understanding cnc milling

understanding cnc milling

CNC milling, or computer numerical control milling, is a machining process which employs computerized controls and rotating multi-point cutting tools to progressively remove material from the workpiece and produce a custom-designed part or product. This process is suitable for machining a wide range of materials, such as metal, plastic, glass, and wood, and producing a variety of custom-designed parts and products.

Several capabilities are offered under the umbrella of precision CNC machining services, including mechanical, chemical, electrical, and thermal processes. CNC milling is a mechanical machining process along with drilling, turning, and a variety of other machining processes, meaning that material is removed from the workpiece via mechanical means, such as the actions of the milling machines cutting tools.

This article focuses on the CNC milling process, outlining the basics of the process, and the components and tooling of the CNC milling machine. Additionally, this article explores the various milling operations and provides alternatives to the CNC milling process.

What is milling? It's is a type of machining that uses cutters to shape a workpiece, often on a moveable tabletop, although some milling machines also feature movable cutters. Milling started out as a manual task performed by humans, but most milling these days is done by a CNC mill, which utilizes a computer to oversee the milling process. CNC milling offers higher precision, accuracy, and production rates, but there are still some situations when manual milling comes in useful. Manual milling, which requires a lot of technical skill and experience, offers shorter turnaround times. It also has the added benefit that manual mills are cheaper and the user doesnt need to worry about programming the machine.

Like most conventional mechanical CNC machiningprocesses, the CNC milling process utilizes computerized controls to operate and manipulate machine tools which cut and shape stock material. In addition, the process follows the same basic production stages which all CNC machining processes do, including:

The CNC milling process begins with the creation of a 2D or 3D CAD part design. Then the completed design is exported to a CNC-compatible file format and converted by CAM software into a CNC machine program which dictates the actions of the machine and the movements of the tooling across the workpiece. Before the operator runs the CNC program, they prepare the CNC milling machine by affixing the workpiece to the machines work surface (i.e., worktable) or workholding device (e.g., vise), and attaching the milling tools to the machine spindle. The CNC milling process employs horizontal or vertical CNC-enabled milling machinesdepending on the specifications and requirements of the milling applicationand rotating multi-point (i.e., multi-toothed) cutting tools, such as mills and drills. When the machine is ready, the operator launches the program via the machine interface prompting the machine to execute the milling operation.

Once the CNC milling process is initiated, the machine begins rotating the cutting tool at speeds reaching up to thousands of RPM. Depending on the type of milling machine employed and the requirements of the milling application, as the tool cuts into the workpiece, the machine will perform one of the following actions to produce the necessary cuts on the workpiece:

As opposed to manual milling processes, in CNC milling, typically the machine feeds moveable workpieces with the rotation of the cutting tool rather than against it. Milling operations which abide by this convention are known as climb milling processes, while contrary operations are known as conventional milling processes.

Generally, milling is best suited as a secondary or finishing process for an already machined workpiece, providing definition to or producing the parts features, such as holes, slots, and threads. However, the process is also used to shape a stock piece of material from start to finish. In both cases, the milling process gradually removes material to form the desired shape and form of the part. First, the tool cuts small piecesi.e., chipsoff the workpiece to form the approximate shape and form. Then, the workpiece undergoes the milling process at much higher accuracy and with greater precision to finish the part with its exact features and specifications. Typically, a completed part requires several machining passes to achieve the desired precision and tolerances. For more geometrically complex parts, multiple machine setups may be required to complete the fabrication process.

CNC milling is a machining process suitable for producing high accuracy, high tolerance parts in prototype, one-off, and small to medium production runs. While parts are typically produced with tolerances ranging between +/- 0.001 in. to +/- 0.005 in., some milling machines can achieve tolerances of up to and greater than +/- 0.0005 in. The versatility of the milling process allows it to be used in a wide range of industries and for a variety of part features and designs, including slots, chamfers, threads, and pockets. The most common CNC milling operations include:

Face milling refers to milling operations in which the cutting tools axis of rotation is perpendicular to the surface of the workpiece. The process employs face milling cutters which have teeth both on the periphery and tool face, with the peripheral teeth primarily being used for cutting and the face teeth being used for finishing applications. Generally, face milling is used to create flat surfaces and contours on the finished piece and is capable of producing higher quality finishes than other milling processes. Both vertical and horizontal milling machines support this process.

Plain milling, also known as surface or slab milling, refers to milling operations in which the cutting tools axis of rotation is parallel to the surface of the workpiece. The process employs plain milling cutters which have teeth on the periphery that perform the cutting operation. Depending on the specifications of the milling application, such as the depth of the cut and the size of the workpiece, both narrow and wide cutters are used. Narrow cutters allow for deeper cuts, while wider cutters are used for cutting larger surface areas. If a plain milling application requires the removal of a large amount of material from the workpiece, the operator first employs a coarse-toothed cutter, slow cutting speeds, and fast feed rates to produce the custom-designed parts approximate geometry. Then, the operator introduces a finer toothed cutter, faster cutting speeds, and slower feed rates to produce the details of the finished part.

Angular milling, also known as angle milling, refers to milling operations in which the cutting tools axis of rotation is at an angle relative to the surface of the workpiece. The process employs single-angle milling cuttersangled based on the particular design being machinedto produce angular features, such as chamfers, serrations, and grooves. One common application of angular milling is the production of dovetails, which employs 45, 50, 55, or 60 dovetail cutters based on the design of the dovetail.

Form milling refers to milling operations involving irregular surfaces, contours, and outlines, such as parts with curved and flat surfaces, or completely curved surfaces. The process employs formed milling cutters or fly cutters specialized for the particular application, such as convex, concave, and corner rounding cutters. Some of the common applications of form milling include producing hemispherical and semi-circular cavities, beads, and contours, as well as intricate designs and complex parts with a single machine setup.

Besides the aforementioned operations, milling machines can be used to accomplish other specialized milling and machining operations. Examples of the other types of milling machine operations available include:

Straddle milling: Straddle milling refers to milling operations in which the machine tool machines two or more parallel workpiece surfaces with a single cut. This process employs two cutters on the same machine arbor, arranged such that the cutters are at either side of the workpiece and can mill both sides at the same time.

Gang milling: What is gang milling? Gang milling refers to milling operations which employ two or more cutterstypically of varying size, shape, or widthon the same machine arbor. Each cutter can perform the same cutting operation, or a different one, simultaneously, which produces more intricate designs and complex parts in shorter production times.

Profile milling: Profile milling refers to milling operations in which the machine tool creates a cut path along a vertical or angled surface on the workpiece. This process employs profile milling equipment and cutting tools which can be either parallel or perpendicular to the workpieces surface.

Gear cutting: Gear cutting is a milling operation which employs involute gear cutters to produce gear teeth. These cutters, a type of formed milling cutters, are available in various shapes and pitch sizes depending on the number of teeth necessary for the particular gear design. A specialized lathe cutter bit can also be employed by this process to produce gear teeth.

Other machining processes: Since milling machines support the use of other machine tools besides milling tools, they can be used for machining processes other than milling, such as drilling, boring, reaming, and tapping.

Like most CNC machining processes, the CNC milling process uses CAD software to produce the initial part design and CAM software to generate the CNC program which provides the machining instructions to produce the part. The CNC program is then loaded to the CNC machine of choice to initiate and execute the milling process.

Column: The column refers to the machine component which provides support and structure to all other machine components. This component includes an affixed base and can include additional internal components which aid the milling process, such as oil and coolant reservoirs.

Knee: The knee refers to the adjustable machine component which is affixed to the column and provides support to the saddle and worktable. This component is adjustable along the Z-axis (i.e., able to be raised or lowered) depending on the specifications of the milling operation.

Saddle: The saddle refers to the machine component located on top of the knee, supporting the worktable. This component is capable of moving parallel to the axis of the spindle, which allows the worktable, and by proxy the workpiece, to be horizontally adjusted.

Worktable: The worktable refers to the machine component located on top of the saddle, which the workpiece or workholding device (e.g., chuck or vise) is fastened. Depending on the type of machine employed, this component is adjustable in the horizontal, vertical, both, or neither direction.

Spindle: The spindle refers to the machine component supported by the column which holds and runs the machine tool (or arbor) employed. Within the column, an electric motor drives the rotation of the spindle.

Arbor: The arbor refers to the shaft component inserted into the spindle in horizontal milling machines in which multiple machine tools can be mounted. These components are available in various lengths and diameters depending on the specifications of the milling application. The types of arbors available include standard milling machine, screw, slitting saw milling cutter, end milling cutter, and shell end milling cutter arbors.

Ram: The ram refers to the machine component, typically in vertical milling machines, located on top of and affixed to the column which supports the spindle. This component is adjustable to accommodate different positions during the milling operation.

Machine tool: The machine tool represents the machine component held by the spindle which performs the material removal operation. The milling process can employ a wide range of milling machine tools (typically multi-point cutters) depending on the specifications of the milling applicatione.g., the material being milled, quality of the surface finish required, machine orientation, etc. Machine tools can vary based on the number, arrangement, and spacing of their teeth, as well as their material, length, diameter, and geometry. Some of the types of horizontal milling machine tools employed include plane, form relieved, staggered tooth, and double angle mills, while vertical milling machine tools employed include flat and ball end, chamfer, face, and twist drill mills. Millings machines can also use drilling, boring, reaming, and tapping tools to perform other machining operations.

In vertical milling machines, the machine spindle is vertically oriented, while in horizontal milling machines the spindle is horizontally oriented. Horizontal machines also employ arbors for additional support and stability during the milling process, and have support capabilities for multiple cutting tools, such as in gang milling and straddle milling. Controls for both vertical and horizontal milling machine are dependent on the type of machine employed. For example, some machines can raise and lower the spindle and laterally move the worktable, while other machines have stationary spindles and worktables which move both horizontally, vertically, and rotationally. When deciding between vertical and horizontal milling machines, manufacturers and job shops must consider the requirements of the milling application, such as the number of surfaces requiring milling and the size and shape of the part. For example, heavier workpieces are better suited for horizontal milling operations, while die sinking applications are better suited for vertical milling operations. Ancillary equipment that modifies vertical or horizontal machines to support the opposing process is also available.

Most CNC milling machines are available with 3 to 5 axes typically providing performance along the XYZ axes and, if applicable, around rotational axes. The X-axis and Y-axis designate horizontal movement (side-to-side and forward-and-back, respectively, on a flat plane), while the Z-axis represents vertical movement (up-and-down) and the W-axis represents diagonal movement across a vertical plane. In basic CNC milling machines, horizontal movement is possible in two axes (XY), while newer models allow for the additional axes of motion, such as 3, 4, and 5-axis CNC machines. Table 1, below, outlines some of the characteristics of milling machines categorized by the number of axes of motion.

Depending on the type of milling machine employed, the machine tool, the machine worktable, or both of the components can be dynamic. Typically, dynamic worktables move along the XY-axes, but they are also capable of moving up and down to adjust the depth of cut and swiveling along the vertical or horizontal axis for an increased range of cutting. For milling applications requiring dynamic tooling, in addition to its inherent rotary motion, the machine tool moves perpendicularly along multiple axes, allowing the tools circumference, rather than just its tip, to cut into the workpiece. CNC milling machines with greater degrees of freedom allow for greater versatility and complexity in the milled parts produced.

There are several different types of milling machines available which are suitable for a variety of machining applications. Beyond classification based solely on either machine configuration or the number of axes of motion, milling machines are further classified based on the combination of their specific characteristics. Some of the most common types of milling machines include:

Knee-type: Knee-type milling machines employ a fixed spindle and vertically adjustable worktable which rests on the saddle supported by the knee. The knee can be lowered and raised on the column depending on the position of the machine tool. Some examples of knee-type milling machines include floor-mounted and bench-type plain horizontal milling machines.

Ram-type: Ram-type milling machines employ a spindle affixed to a movable housing (i.e., ram) on the column, which allows the machine tool to move along the XY axes. Two of the most common ram-type milling machines include floor-mounted universal horizontal and swivel cutter head milling machines.

Bed-type: Bed-type milling machines employ worktables affixed directly to the machine bed, which prevents the workpiece from moving along both the Y-axis and Z-axis. The workpiece is positioned beneath the cutting tool, which, depending on the machine, is capable of moving along the XYZ axes. Some of the bed-type milling machines available include simplex, duplex, and triplex milling machines. While simplex machines employ one spindle which moves along either the X-axis or Y-axis, duplex machines employ two spindles, and triplex machines employ three spindles (two horizontal and one vertical) for machining along the XY and XYZ axes, respectively.

Planer-type: Planer-type milling machines are similar to bed-type milling machines in that they have worktables fixed along the Y-axis and Z-axis and spindles capable of moving along the XYZ axes. However, planer-type machines can support multiple machine tools (typically up to four) simultaneously, which reduces the lead time for complex parts.

Some of the specialized types of milling machines available include rotary table, drum, and planetary milling machines. Rotary table milling machines have circular worktables which rotate around the vertical axis and employ machine tools positioned at varying heights for roughing and finishing operations. Drum milling machines are similar to rotary table machines, except the worktable is referred to as a drum and it rotates around the horizontal axis. In planetary machines, the worktable is stationary, and the workpiece is cylindrical. The rotating machine tool moves across the surface of the workpiece cutting internal and external features, such as threads.

The CNC milling process is best suited as a secondary machining process to provide finishing features to a custom-designed part, but can also be used to produce custom designs and specialty parts from start to finish. CNC milling technology allows the process to machine parts of a wide range of materials, including:

As with all machining processes, when selecting a material for a milling application, several factors must be considered, such as the properties of the material (i.e., hardness, tensile and shear strength, and chemical and temperature resistance) and the cost-effectiveness of machining the material. These criteria dictate whether the material is suitable for the milling process and the budgetary constraints of the milling application, respectively. The chosen material determines the type(s) of the machine tool(s) employed and its/their design(s), and the optimal machine settings, including cutting speed, feed rate, and depth of cut.

CNC milling is a mechanical machining process suitable for machining a wide range of materials and producing a variety of custom-designed parts. While the process may demonstrate advantages over other machining processes, it may not be appropriate for every manufacturing application, and other processes may prove more suitable and cost-effective.

Some of the other more conventional mechanical machining processes available include drilling and turning. Drilling, like milling, typically employs multi-point tools (i.e., drill bits), while turning employs single-point tools. However, while in turning the workpiece can be moved and rotated similar to that of some milling applications, in drilling the workpiece is stationary throughout the drilling operation.

Some of the non-conventional mechanical machining processes (i.e., do not employ machine tools but still employ mechanical material removal processes) include ultrasonic machining, waterjet cutting, and abrasive jet machining. Non-conventional, non-mechanical machining processesi.e., chemical, electrical, and thermal machining processesprovide additional alternative methods of removing material from a workpiece which do not employ machine tools or mechanical material removal processes, and include chemical milling, electrochemical deburring, laser cutting, and plasma arc cutting. These non-conventional machining methods support the production of more complex, demanding, and specialized parts not typically possible through conventional machining processes.

Outlined above are the basics of the CNC milling process, various CNC milling operations and their required equipment, and some of the considerations that may be taken into account by manufacturers and machine shops when deciding whether CNC milling is the most optimal solution for their particular machining application.

To find more information on domestic commercial and industrial suppliers of custom manufacturing services and equipment, visit the Thomas Supplier Discovery Platform, where you will find information on over 500,000 commercial and industrial suppliers.

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used ball mills | ball mills for sale | phoenix equipment

used ball mills | ball mills for sale | phoenix equipment

Why buy a brand new ball mill when we have high-quality used and refurbished ball mills for sale? Well-made industrial equipment from top manufacturers maintain their value and save your company or industry substantially.

Ball mills are a fundamental part of the manufacturing industry in the USA as well as around the world. Ball mills crush material into various sizes and extract resources from mined materials. Pebble mills are a type of ball mill and are also used to reduce the size of hard materials, down to 1 micron or less.

Because of their fairly simple design, ball mills and pebble mills are less likely to need costly repairs (unlike other crushing or extraction equipment) making them an attractive option for businesses on a budget.

Unused 24 x 41 Polysius EGL Ball Mill. Steel Lined. Twin 7MW Electric Motor Drives, 14MW/11kV Power Supply Unit. Twin Combiflex Fixed Speed Gear Drive. Auxiliary Drive Motors, Lubrication Unit Fixed Bearing and Lubrication Unit Floating Bearing, Frozen Charge Protection System, Vibration Sensors for COMBIFLEX, Dam Ring, Permanent installed Centrifuge for Fixed Bearing, Closed Circuit Chiller Unit, Insurance and Commissioning Spares, Special Tools. Qty 2 Available.

Used 11.5' diameter X 17' long ball mill. Manufactured by KVS (Kennedy Van Saun). 1000 HP open winding synchronous motor. Features trommel discharge and feed tank. Refurbished in 2013, which included installation of new oil jacking system, oil lube system for Babbitt bearings, new titanium steel water jet-machined discharge grates, and motor refurbishment. Set of new babbit bearings available. Previously operated as a closed circuit dry mill with grinding capacity of 40 metric tons per hour with output fineness of >80% passing 200 mesh. Motor operating speed of 15.8 RPM charged with approximately 78 tons of 1", 2" and 3" steel balls. Last used at a phosphate processing facility and in good condition.

Used 8' x 10' Epworth 200 HP jacketed steel ball mill, approximately 8' diameter x 10' long, jacketed chamber, gear and pinion driven with approximately 200 motor drive, on stands, Serial# K-0845.

Used 175HP Hosokawa Alpine Super Orion Continuous Ball mill. Model 195/495 CLKE. Alumina Oxide lined. 195 cm (76")inner diameter x 495 cm (194") long drum, periphery dry discharge with adjustable discharge openings, enclosed discharge housing, direct driven thru gearbox. 175HP 460 volt motor with VFD motor controller. Serial# C1198474. Built 2012.

Used 6' x 8' Paul Abbe jacketed 100 HP steel ball mill, approximately 6' diameter x 8' long, jacketed chamber, gear and pinion driven with approximately 100 motor drive, on stands.

Unused 5' diameter X 6' long Steel Lined Ball Mill, manufactured by Patterson Industries, Type D, non-jacketed, with AR400 steel liners. Includes 30 HP, 3 phase, 60 Hz, 230-460 V, 1725 RPM motor. Mill drive is integrally coupled to horizontal parallel shafted helical gear reducer. Continuous type, with product feeding through spiral inlet trunnion and exiting through the discharge end trunnion. Features cylinder manway access door for cleaning. Internal volume measures approximately 839 USG (112 CF). Mill shell is lined with (24) 1/4" thick liner plates, each head lined with (8) 3/8" thick pie-shaped liner plates. Mounted on stand with approximately 66" clearance between the mill cylinder and floor. Mills were intended for use in glass particle size reduction but were never installed. Manufactured in 2019, units are still in factory plastic wrap and in new condition. (Qty - 2 available)

Used 5 ft. dia. x 6 ft. (Approx 120 Cu.Ft) Patterson Pebble Mill. Alumina brick lining. On stand with 20 HP motor and gear reduced drive with brake. Bull gear and pinion. Babbit bearings. Door is polyurethane and has a drain with plug.

Used 4' x 5' (345 Gallon Total/210 Gallon Working) Ball Mill. Mfg Steveco. Steel Lining. Jacketed. 20 HP (460V/60Hz/3ph) Gear Reduced heavy duty drive on high stands. Solid door and discharge door.

Used Paul O. Abbe One Piece Ceramic Ball Mill, Model JM-300. Non-Jacketed chamber approximate 24.8" diameter x 39.5" long. Vessel volume 300 liter (79 gallons). Approximate 5" charge and discharge port with cover. Driven by a 3 HP, 3/60/208-230/460 volt 1760 rpm motor with a shaft mounted Sumitomo Model 203E-25 reducer. Approximate 32 rpm drum speed. Includes a control panel with an ABB drive. Mounted on a common carbon steel frame legs. Serial # 0830032JM. Built 2008.

Used 28 Gallon Paul O. Abbe Ceramic Jar / Ball Mill. Approximate 3.7 Cubic Feet. Approximate 20" diameter x 20" straight side. Includes motor and cage. Mounted on a carbon steel frame with safety cage.

Used 30 gallon Paul O. Abbe Jar Mill. Porcelain jar 21" diameter x 18" straight side. Driven by 1hp, 1/60/115/230 volt, 1740 rpm motor thru a reducer, ratio 9.3 to 1. Inlet & outlet with cover and clamp. Mounted on carbon steel legs with a discharge housing. Serial#84876

Used 25 Gallon Norton Chemical Process Products Jar Mill. Porcelain jar 20" diameter x 20" straight side. Driven by 1hp, 3/60/230/460 volt, 1730 rpm motor thru a reducer, no ratio. Inlet & outlet with cover and clamp. Mounted on carbon steel legs with a discharge housing. Serial# AV-83104.

Used 35.30 Gallon Paul O. Abbe Jar Mill. Model 5A Porcelain jar 22" diameter x 20" straight side. Driven by 1hp, 3/60/230/460 volt, 1745 rpm motor thru a reducer, ratio 25 to 1. Inlet & outlet with cover and clamp. Mounted on carbon steel legs with a discharge housing. Serial#A41563.

Unused 24 x 41 Polysius EGL Ball Mill. Steel Lined. Twin 7MW Electric Motor Drives, 14MW/11kV Power Supply Unit. Twin Combiflex Fixed Speed Gear Drive. Auxiliary Drive Motors, Lubrication Unit Fixed Bearing and Lubrication Unit Floating Bearing, Frozen Charge Protection System, Vibration Sensors for COMBIFLEX, Dam Ring, Permanent installed Centrifuge for Fixed Bearing, Closed Circuit Chiller Unit, Insurance and Commissioning Spares, Special Tools. Qty 2 Available.

Used 11.5' diameter X 17' long ball mill. Manufactured by KVS (Kennedy Van Saun). 1000 HP open winding synchronous motor. Features trommel discharge and feed tank. Refurbished in 2013, which included installation of new oil jacking system, oil lube system for Babbitt bearings, new titanium steel water jet-machined discharge grates, and motor refurbishment. Set of new babbit bearings available. Previously operated as a closed circuit dry mill with grinding capacity of 40 metric tons per hour with output fineness of >80% passing 200 mesh. Motor operating speed of 15.8 RPM charged with approximately 78 tons of 1", 2" and 3" steel balls. Last used at a phosphate processing facility and in good condition.

Used 8' x 10' Epworth 200 HP jacketed steel ball mill, approximately 8' diameter x 10' long, jacketed chamber, gear and pinion driven with approximately 200 motor drive, on stands, Serial# K-0845.

Used 175HP Hosokawa Alpine Super Orion Continuous Ball mill. Model 195/495 CLKE. Alumina Oxide lined. 195 cm (76")inner diameter x 495 cm (194") long drum, periphery dry discharge with adjustable discharge openings, enclosed discharge housing, direct driven thru gearbox. 175HP 460 volt motor with VFD motor controller. Serial# C1198474. Built 2012.

Used 6' x 8' Paul Abbe jacketed 100 HP steel ball mill, approximately 6' diameter x 8' long, jacketed chamber, gear and pinion driven with approximately 100 motor drive, on stands.

Unused 5' diameter X 6' long Steel Lined Ball Mill, manufactured by Patterson Industries, Type D, non-jacketed, with AR400 steel liners. Includes 30 HP, 3 phase, 60 Hz, 230-460 V, 1725 RPM motor. Mill drive is integrally coupled to horizontal parallel shafted helical gear reducer. Continuous type, with product feeding through spiral inlet trunnion and exiting through the discharge end trunnion. Features cylinder manway access door for cleaning. Internal volume measures approximately 839 USG (112 CF). Mill shell is lined with (24) 1/4" thick liner plates, each head lined with (8) 3/8" thick pie-shaped liner plates. Mounted on stand with approximately 66" clearance between the mill cylinder and floor. Mills were intended for use in glass particle size reduction but were never installed. Manufactured in 2019, units are still in factory plastic wrap and in new condition. (Qty - 2 available)

Used 5 ft. dia. x 6 ft. (Approx 120 Cu.Ft) Patterson Pebble Mill. Alumina brick lining. On stand with 20 HP motor and gear reduced drive with brake. Bull gear and pinion. Babbit bearings. Door is polyurethane and has a drain with plug.

Used 4' x 5' (345 Gallon Total/210 Gallon Working) Ball Mill. Mfg Steveco. Steel Lining. Jacketed. 20 HP (460V/60Hz/3ph) Gear Reduced heavy duty drive on high stands. Solid door and discharge door.

Used Paul O. Abbe One Piece Ceramic Ball Mill, Model JM-300. Non-Jacketed chamber approximate 24.8" diameter x 39.5" long. Vessel volume 300 liter (79 gallons). Approximate 5" charge and discharge port with cover. Driven by a 3 HP, 3/60/208-230/460 volt 1760 rpm motor with a shaft mounted Sumitomo Model 203E-25 reducer. Approximate 32 rpm drum speed. Includes a control panel with an ABB drive. Mounted on a common carbon steel frame legs. Serial # 0830032JM. Built 2008.

Used 28 Gallon Paul O. Abbe Ceramic Jar / Ball Mill. Approximate 3.7 Cubic Feet. Approximate 20" diameter x 20" straight side. Includes motor and cage. Mounted on a carbon steel frame with safety cage.

Used 30 gallon Paul O. Abbe Jar Mill. Porcelain jar 21" diameter x 18" straight side. Driven by 1hp, 1/60/115/230 volt, 1740 rpm motor thru a reducer, ratio 9.3 to 1. Inlet & outlet with cover and clamp. Mounted on carbon steel legs with a discharge housing. Serial#84876

Used 25 Gallon Norton Chemical Process Products Jar Mill. Porcelain jar 20" diameter x 20" straight side. Driven by 1hp, 3/60/230/460 volt, 1730 rpm motor thru a reducer, no ratio. Inlet & outlet with cover and clamp. Mounted on carbon steel legs with a discharge housing. Serial# AV-83104.

Used 35.30 Gallon Paul O. Abbe Jar Mill. Model 5A Porcelain jar 22" diameter x 20" straight side. Driven by 1hp, 3/60/230/460 volt, 1745 rpm motor thru a reducer, ratio 25 to 1. Inlet & outlet with cover and clamp. Mounted on carbon steel legs with a discharge housing. Serial#A41563.

Phoenix Equipment is a global supplier of used ball mills. We have new, used and reconditioned ball mills from leading manufacturers, including: Paul O. Abbe Retsch Epworth Patterson Netzsch Newell Dunford Marcy Denver FL Smidth Nordberg Allis Chalmers Metso Hardinge Kurimoto Iron Works Kobe-Allis Chalmers Stevenson Fuller-Traylor Steveco Western Machinery Marion Machine Makrum and more. Ball mills are used in a wide-range of industrial applications: cement processing, paint dyes and pigmentation processing, coal and ore processing, chemical processing and pyrotechnics, and many others. Ball milling has several key advantages over other systems: cost of the grinding medium and installation is generally low works for batch or continuous operation (as well as closed-circuit grinding) suitable for a wide range of materials simple design ensures less repairs Whether you are in the market for a used ball mill for your business or you have a pre-owned ball mill youd like to sell, USA-based Phoenix Equipment can help. Contact us today to learn more about what Phoenix can do for you. Related equipment: Agitators, Screen/Separators, Kilns and Calciners, Scales and Extruders. Fill out our quick and easy quote form for more information about our Ball Mills inventory.

Ball mills are used in a wide-range of industrial applications: cement processing, paint dyes and pigmentation processing, coal and ore processing, chemical processing and pyrotechnics, and many others.

Whether you are in the market for a used ball mill for your business or you have a pre-owned ball mill youd like to sell, USA-based Phoenix Equipment can help. Contact us today to learn more about what Phoenix can do for you.

Phoenix Equipment buys and sells used chemical process equipment and plants for relocation. Our industry focus includes process plants and machinery in the chemical, petrochemical, fertilizer, refining, gas processing, power generation, pharmaceutical and food manufacturing industries. We have extensive experience acquiring processing plants and process lines that require the execution of complex dismantlement, demolition and decommissioning projects. Based in Red Bank, New Jersey, USA, we have team members located in China, India, Germany and relationships throughout the world.

Why Use Phoenix for Your Plant Dismantling & Plant Relocation Needs A Common Plant Liquidation Scenario Your company has made the tough decision to close a plant. This plant was running for years, and the company paid a lot to have it built, paid everyones salaries, and maintained or even modernized all of the production assets over the plants life but the plant needs to be sold off for one reason or another. Your company has called upon you to recover as much dollar as you can to help keep the organization alive, and better yet, healthy, in what is a constant battle in the marketplace. Youve either: Have spent months, maybe even years trying to find a buyer that would operate the plant in place, without any success, while the plants assets lose value every passing day. Or, you cant sell it to another company, as you are one of the few suppliers of the product the plant makes, and you dont want to create a competitor, or improve a competitors position. Or, the plant is on leased propert

Hydrogenation: Major Applications Hydrogenation is a billion-dollar industry. Hydrogenating means to add hydrogen to something. According to Haldor Topsoe, hydrogenation comprises 48% of total hydrogen consumption, 44% of which is for hydrocracking and hydrotreating in refineries , and 4% for hydrogenation of unsaturated hydrocarbons (including hardening of edible oil) and of aromatics, hydrogenation of aldehydes and ketones (for instance oxo-products), and hydrogenation of nitrobezene (for manufacture of aniline). Hydrocracking & Hydrotreating Industrially, hydrotreating and hydrocracking are performed in down flow trickle bed reactors, where the gas and the liquid feed are sent concurrently through a fixed bed plug flow reactor. Although the flow pattern in the reactor can be reasonably approximated, the observed kinetics in such a trickle bed reactor are quite often affected by minor unplanned oscillations in the flow. How the gas and liquid collide and mix together affects the end prod

Thermoplastics A Focus on Polyethylene & Polypropylene Thermoplastics are a class of polymers, that with the application of heat, can be softened and melted, and can be processed either in the heat-softened state (e.g. by thermoforming) or in the liquid state (e.g. by extrusion and injection molding). Over 70% of the plastics used in the world are thermoplastics, and the two most commonly used thermoplastics are both olefins, compound made up of hydrogen and carbon that contains one or more pairs of carbon atoms linked by a double bond. These two olefins are polyethylene and polypropylene. Polyethylene Polyethylene is a tough, light, flexible synthetic resin made by polymerizing ethylene, chiefly used for plastic bags, food containers, and other packaging. It may be of low density or high density depending upon the process used in its manufacturing. It is resistant to moisture and most of the chemicals. It can be heat sealed and is flexible at room temperature (and low temperature), and in additional to its material properties,

small ball mills for sale

small ball mills for sale

Our small-scale miners Ball Mills use horizontal rotating cylinders that contain the grinding media and the particles to be broken. The mass moves up the wall of the cylinder as it rotates and falls back into the toe of the mill when the force of gravity exceeds friction and centrifugal forces. Particles are broken in the toe of the mill when caught in the collisions between the grinding media themselves and the grinding media and the mill wall. In ball mills, the grinding media and particles acquire potential energy that becomes kinetic energy as the mass falls from the rotating shell. Ball mills are customarily divided into categories that are mainly defined by the size of the feed particles and the type of grinding media.

Intermediate and fine size reduction by grinding is frequently achieved in a ball mill in which the length of the cylindrical shell is usually 1 to 1.5 times the shell diameter. Ball mills of greater length are termed tube mills, and when hard pebbles rather than steel balls are used for the grinding media, the mills are known as pebble mills. In general, ball mills can be operated either wet or dry and are capable of producing products on the order of 100 um. This duty represents reduction ratios as great as 100.

The ball mill, an intermediate and fine-grinding device, is a tumbling drum with a 40% to 50% filling of balls. The material that is to be ground fills the voids between the balls. The tumbling balls capture the particles in ball/ball or ball/liner events and load them to the point of fracture. Very large tonnages can be ground with these devices because they are very effective material handling devices. The feed can be dry, with less than 3% moisture to minimize ball coating, or a slurry can be used containing 20% to 40% water by weight. Ball mills are employed in either primary or secondary grinding applications. In primary applications, they receive their feed from crushers, and in secondary applications, they receive their feed from rod mills, autogenous mills, or semi-autogenous mills. Regrind mills in mineral processing operations are usually ball mills, because the feed for these applications is typically quite fine. Ball mills are sometimes used in single-stage grinding, receiving crusher product. The circuits of these mills are often closed with classifiers at high-circulating loads.

All ball mills operate on the same principles. One of these principles is that the total weight of the charge in the mill-the sum of the weight of the grinding media, the weight of the material to be ground, and any water in the millis a function of the percentage of the volume of the mill it occupies.

The power the mill draws is a function of the weight of the charge in the mill, the %of volumetric loading of the mill, the %of critical speed, which is the speed in RPM at which the outer layer of the charge in the mill will centrifuge.

For closed grinding circuits producing typical ball mill products, indirect and direct on-line measurements of the product size are available. The indirect means are those which assume that the product size is relatively constant when the feed condition to the classifying unit and the operating conditions in the classifying unit are constant. One example is maintaining a constant mass flow, pulp density and pressure in the feed to the cyclone classifier.

By using math modeling, it is possible to calculate the product size from measured cyclone classifier feed conditions and circuit operating data, thus establishing the effect on the particle size distribution in the product for changes in the variables.

Direct on-line means to measure either particle size or surface area are available for typical ball mill circuit products. These require the means to obtain representative or at least consistent samples from the grinding circuit product stream. These direct means and the calculated product particle size distributions can be used to:

Small variations in the feed size to ball mill circuits generally is not critical to the calculation of operating work index because they make a very small change in the 10F factor. Thus, a computer program can be developed to calculate operating work indices from on-line data with the feed size a constant and with the program designed to permit manually changing this value, as required to take into account changes in feed size resulting from such things as drawing down feed bins, crusher maintenance, work screen surfaces in the crushing plant, etc. which are generally known in advance, or can be established quickly. Developments underway for on-line measurement of particle size in coarser material which when completed will permit measuring the feed size used to calculate operating work indices.

recorded by a data logger, gives continuous means to report comminution circuit performance and evaluate in-plant testing. Changes in Wio indicated on data loggers alert operating and supervisory personnel that a change has occurred in either the ore or in circuit performance. If sufficient instrumentation is available, the cause for a problem can often be located from other recorded or logged data covering circuit and equipment operation, however, generally the problem calls for operator attention to be corrected.

Wio can be used to determine the efficiency of power utilization for the entire comminution section of a mill, and for the individual circuits making up the comminution section. The efficiency of a comminution circuit is determined by the following equation.

Wi is obtained by running the appropriate laboratory tests on a composite sample of circuit feed. Wio is calculated from plant operating data covering the period when the feed sample was taken. Since Wi from laboratory tests refers to specific conditions for accurate efficiency determinations, it is necessary to apply correction factors as discussed in The Tools of Power Power to Wio to put the laboratory and operating data on the same basis.

To-date, there is no known way to obtain standard work index data from on-line tests. Continuous measurement of comminution circuit efficiency is not possible and thus efficiency is not available for circuit control. Using laboratory data and operating data, efficiency can be determined for overall section and individual circuit for evaluation and reporting. Just monitoring Wio and correcting operating problems as they occur will improve the utilization of the power delivered to the comminution circuits.

Samples taken from the chips around blast hole drillings and from broken ore in the pit or mine for laboratory work index and other ore characteristic determinations before the ore is delivered to the mill, can be used to predict in advance comminution circuit performance. Test results can also be used for ore blending to obtain a more uniform feed, particularly to primary autogenous and semi-autogenous circuits.

We sell Small Ball Mills from 2 to 6 (600 mm X 1800 mm) in diameter and as long as 10 (3000 mm) in length. The mills are manufactured using a flanged mild steel shell, cast heads, overflow discharge, removable man door, spur type ring gear, pinion gear assembly with spherical roller bearings, replaceable roller bronze trunnion bearings, oil lubrication, replaceable trunnion liners with internal spirals, rubber liners and lifters, feed spout with wash port, discharge trommel with internal spiral, motor and gear reducer drive, direct coupled to pinion gear, gear guard and modular steel support frame. All ball mills always come withOSHA-type gear guard.

A PULP level sufficiently high to interpose a bed of pulp, partly to cushion the impact of the balls, permits a maximum crushing effect with a minimum wear of steel. The pulp level of theseSmall Ball Millscan be varied from discharging at the periphery to discharging at a point about halfway between the trunnion and the periphery.The mill shell is of welded plate steel with integral end flanges turned for perfect alignment, and the heads are semi-steel, with hand holes in the discharge end through which the diaphragm regulation is arranged with plugs.The trunnion bearings are babbitted, spherical, cast iron, and of ample size to insure low bearing pressure; while the shell and saddle are machined to gauge so that the shells are interchangeable.

Data based on:Wet grinding, single stage, closed circuit operation: feed:( one way dimension); Class III ore. All mills:free discharge, grated type, rapid pulp flow. N. B.for overflow type mills: capacity 80%power 83%. Dimensions :diameters inside shell without linerslengths working length shell between end liners.

The CIW is a Small Ball Mill thats belt driven, rigid bearing, wet grinding, trunnion or grate discharge type mill with friction clutch pulley and welded steel shell. The 7 and 8 foot diameter mills are of flange ring construction with cut gears while all other sizes have cast tooth gears. All these mills are standard with white iron bar wave type shell liners except the 8 foot diameter mill which is equipped with manganese steel liners. The horsepowers shown in the table are under running conditions so that high torque or wound rotor (slip ring) motors must be used. Manganese or alloy steel shell or head liners and grates can be supplied with all sizes of mills if required. Alloy steel shell liners are recommended where 4 or larger balls are used and particularly for the larger sized mills.

Small (Muleback Type) Ball Mill is built for muleback transportation in 30 and 3 diameters (inside liners). A 4 (Muleback Type) Ball Mill is of special design and will be carefully considered upon request. Mankinds search for valuable minerals often leads him far away from modern transportation facilities. The potential sources of gold, silver and strategic minerals are often found by the prospector, not close by our modern highways, but far back in the mountains and deserts all over the world. The Equipment Company has realized this fact, and therefore has designed a Ball Mill that can be transported to these faraway and relatively inaccessible properties, either by the age old muleback transportation system, or by the modern airplane. As a result these properties may now obtain a well-designed ball mill with the heaviest individual piece weighing only 350 pounds.

The prime factor considered in this design was to furnish equipment having a maximum strength with a minimum weight. For this reason, these mills are made of steel, giving a high tensile strength and light weight to the mills. The muleback design consists of the sturdy cast iron head construction on the 30 size and cast steel head construction on the larger sizes. The flanges on the heads are arranged to bolt to the rolled steel shell provided with flanged rings. When required, the total length of the shell may consist of several shell lengths flanged together to provide the desired mill length. Liners, bearings, gears and drives are similar to those standard on all Ball Mills.

This (Convertible) and Small Ball Mill is unique in design and is particularly adapted to small milling plants. The shell is cast in one piece with a flange for bolting to the head. In converting the mill from a 30x 18 to a 30x 36 unit with double the capacity, it is only necessary to secure a second cast shell (a duplicate of the first) and bolt it to the original section.

30 Convertible Ball Mills are furnished with scoop feeders with replaceable lips. Standard mills are furnished with liners to avoid replacement of the shell; however, themill can be obtained less liners. This ball mill is oftendriven by belts placed around the center, although gear drive units with cast gears can be furnished. A Spiral Screen can be attached to the discharge.

This mill may be used for batch or intermittent grinding, or mixing of dry or wet materials in the ore dressing industry, metallurgical, chemical, ceramic, or paint industries. The material is ground and mixed in one operation by rotating it together with balls, or pebbles in a hermetically sealed cylinder.

The cast iron shell which is bolted to the heads is made with an extra thick wall to give long wearing life. Two grate cleanout doors are provided on opposite sides of the shell by means of which the mill can be either gradually discharged and washed, while running, or easily and rapidly emptied and flushedout while shut down. Wash-water is introduced into the interior of the mill through a tapped opening in the trunnion. The mill may be lined with rubber, silex (buhrstone) or wood if desired.

The Hardinge Conical Ball Mill has been widely used with outstanding success in grinding many materials in a wide variety of fields. The conical mill operates on the principle of an ordinary ball mill with a certain amount of classification within the mill itself, due to its shape.

Sizes of conical mills are given in diameter of the cylindrical section in feet and the length of the cylindrical section in inches. Liners can be had of hard iron, manganese steel or Belgian Silex. Forged steel balls or Danish Flint Pebbles are used for the grinding media, depending upon the material being milled.

The Steel Head Ball-Rod Mill gives the ore dressing engineer a wide choice in grinding design so that he can easily secure a Ball-Rod Mill suited to his particular problem. The successful operation of any grinding unit is largely dependent on the method of removing the ground pulp. The Ball-Rod Mill is available with five types of discharge trunnions, each type obtainable in small, medium or large diameters. The types of discharge trunnions are:

The superiority of the Steel Head Ball-Rod Mill is due to the all steel construction. The trunnions are an integral part of the cast steel heads and are machined with the axis of the mill. The mill heads are assured against breakage due to the high tensile strength of cast steel as compared to that of the cast iron head found on the ordinary ball mill. Trunnion Bearings are made of high- grade nickel babbitt.

Steel Head Ball-Rod Mills can be converted intolarger capacity mills by bolting an additional shell lengthonto the flange of the original shell. This is possible because all Steel Head Ball or Rod Mills have bearings suitable for mills with length twice the diameter.

Head and shell liners for Steel Head Ball-Rod Mills are available in Decolloy (a chrome-nickel alloy), hard iron, electric steel, molychrome steel, and manganese steel. Drive gears are furnished either in cast tooth spur gear and pinion or cut tooth spur gear and pinion. The gears are furnished as standard on the discharge end of the mill, out of the way of the classifier return feed, but can be furnished at the mill feed end by request. Drives may be obtained according to the customers specifications.

Thats one characteristic of Traylor Ball Millsliked by ownersthey are built not only to do a first class job at low cost but to keep on doing it, year after year. Of course, that means we do not build as many mills as if they wore out quicklyor would we? but much as welike order, we value more the fine reputationTraylor Ball Mills have had for nearly threedecades.

Thats one characteristic of Traylor Ball Mills We dont aim to write specifications into thisliked by ownersthey are built not only to do advertisementlet it suffice to say that theresa first class job at low cost but to keep on do- a Traylor Ball Mills that will exactly fit anyanything it, year after year. Of course, that means requirement that anyone may have.

If this is true, there is significance in the factthat international Nicked and Climax Molybdenum, theworlds largest producers of two important steel alloys, areboth users of MARCY Mills exclusively. With international interest centered on increasingproduction of gold, it is even more significant that MARCYMills are the predominant choice of operators in everyimportants gold mining camp in the world.

Ball Mill. Intermediate and fine size reduction by grinding is frequently achieved in a ball mill in which the length of the cylindrical shell is usually 1 to 1.5 times the shell diameter. Ball mills of greater length are termed tube mills, and when hard pebbles rather than steel balls are used for the grinding media, the mills are known as pebble mills. In general, ball mills can be operated either wet or dry and are capable of producing products on the order of 100 pm. This duty represents reduction ratios as great as 100.

The ball mill, an intermediate and fine-grinding device, is a tumbling drum with a 40% to 50% filling of balls (usually steel or steel alloys). The material that is to be ground fills the voids between the balls. The tumbling balls capture the particles in ball/ball or ball/liner events and load them to the point of fracture. Very large tonnages can be ground with these devices because they are very effective material handling devices. The feed can be dry, with less than 3% moisture to minimize ball coating, or a slurry can be used containing 20% to 40% water by weight. Ball mills are employed in either primary or secondary grinding applications. In primary applications, they receive their feed from crushers, and in secondary applications, they receive their feed from rod mills, autogenous mills, or semiautogenous mills. Regrind mills in mineral processing operations are usually ball mills, because the feed for these applications is typically quite fine. Ball mills are sometimes used in single-stage grinding, receiving crusher product. The circuits of these mills are often closed with classifiers at high-circulating loads.

These loads maximize throughput at a desired product size. The characteristics of ball mills are summarized in the Table, which lists typical feed and product sizes. The size of the mill required to achieve a given task-that is, the diameter (D) inside the liners-can be calculated from the design relationships given. The design parameters must be specified.

The liner- and ball-wear equations are typically written in terms of an abrasion index (Bond 1963). The calculated liner and ball wear is expressed in kilograms per kilowatt-hour (kg/kWh), and when multiplied by the specific power (kWh/t), the wear rates are given in kilograms per ton of feed. The wear in dry ball mills is approximately one-tenth of that in wet ball mills because of the inhibition of corrosion. The efficiency of ball mills as measured relative to single-particle slow-compression loading is about 5%. Abrasion indices for five materials are also listed in the Table.

The L/D ratios of ball mills range from slightly less than 1:1 to something greater than 2:1. The tube and compartment ball mills commonly used in the cement industry have L/D ratios 2.75:1 or more. The fraction of critical speed that the mill turns depends on the application, and most mills operate at around 75% of critical speed. Increased speed generally means increased power, but as the simulations presented in Figure 3.26 show, it can also produce more wasted ball impacts on the liners above the toe. causing more wear and less breakage.

There are three principal forms of discharge mechanism. In the overflow ball mill, the ground product overflows through the discharge end trunnion. A diaphragm ball mill has a grate at thedischarge end. The product flows through the slots in the grate. Pulp lifters may be used to discharge the product through the trunnion, or peripheral ports may be used to discharge the product.

The majority of grinding balls are forged carbon or alloy steels. Generally, they are spherical, but other shapes have been used. The choice of the top (or recharge) ball size can be made using empirical equations developed by Bond or Azzaroni or by using special batch-grinding tests interpreted in the content of population balance models. The effect of changes in ball size on specific selection functions has been found to be different for different materials. A ball size-correction method can be used along with the specific selection function scale-up method to determine the best ball size. To do this, a set of ball size tests are performed in a batch mill from which the specific selection function dependence on ball size can be determined. Then, the mill capacities used to produce desired product size can be predicted by simulation using the kinetic parameter corresponding to the different ball sizes.

The mill liners used are constructed from cast alloy steels, wear-resistant cast irons, or polymer (rubber) and polymer metal combinations. The mill liner shapes often recommended in new mills are double-wave liners when balls less than 2.5 in. are used and single-wave liners when larger balls are used. Replaceable metal lifter bars are sometimes used. End liners are usually ribbed or employ replaceable lifters.

The typical mill-motor coupling is a pinion and gear. On larger mills two motors may be used, and in that arrangement two pinions drive one gear on the mill. Synchronous motors are well suited to the ball mill, because the power draw is almost constant. Induction, squirrel cage, and slip ring motors are also used. A high-speed motor running 600 to 1,000 rpm requires a speed reducer between the motor and pinion shaft. The gearless drive has been installed at a number of locations around the world.

what's the difference between sag mill and ball mill - jxsc machine

what's the difference between sag mill and ball mill - jxsc machine

A mill is a grinder used to grind and blend solid or hard materials into smaller pieces by means of shear, impact and compression methods. Grinding mill machine is an essential part of many industrial processes, there are mainly five types of mills to cover more than 90% materials size-reduction applications.

Do you the difference between the ball mill, rod mills, SAG mill, tube mill, pebble mill? In the previous article, I made a comparison of ball mill and rod mill. Today, we will learn about the difference between SAG mill vs ball mill.

AG/SAG is short for autogenous mill and semi-autogenous mill, it combines with two functions of crushing and grinding, uses the ground material itself as the grinding media, through the mutual impact and grinding action to gradually reduce the material size. SAG mill is usually used to grind large pieces into small pieces, especially for the pre-processing of grinding circuits, thus also known as primary stage grinding machine. Based on the high throughput and coarse grind, AG mills produce coarse grinds often classify mill discharge with screens and trommel. SAG mills grinding media includes some large and hard rocks, filled rate of 9% 20%. SAG mill grind ores through impact, attrition, abrasion forces. In practice, for a given ore and equal processing conditions, the AG milling has a finer grind than SAG mills.

The working principle of the self-grinding machine is basically the same as the ball mill, the biggest difference is that the sag grinding machine uses the crushed material inside the cylinder as the grinding medium, the material constantly impacts and grinding to gradually pulverize. Sometimes, in order to improve the processing capacity of the mill, a small amount of steel balls be added appropriately, usually occupying 2-3% of the volume of the mill (that is semi-autogenous grinding).

High capacity Ability to grind multiple types of ore in various circuit configurations, reduces the complexity of maintenance and coordination. Compared with the traditional tumbling mill, the autogenous mill reduces the consumption of lining plates and grinding media, thus have a lower operation cost. The self-grinding machine can grind the material to 0.074mm in one time, and its content accounts for 20% ~ 50% of the total amount of the product. Grinding ratio can reach 4000 ~ 5000, more than ten times higher than ball, rod mill.

Ball mills are fine grinders, have horizontal ball mill and vertical ball mill, their cylinders are partially filled with steel balls, manganese balls, or ceramic balls. The material is ground to the required fineness by rotating the cylinder causing friction and impact. The internal machinery of the ball mill grinds the material into powder and continues to rotate if extremely high precision and precision is required.

The ball mill can be applied in the cement production plants, mineral processing plants and where the fine grinding of raw material is required. From the volume, the ball mill divide into industrial ball mill and laboratory use the small ball mill, sample grinding test. In addition, these mills also play an important role in cold welding, alloy production, and thermal power plant power production.

The biggest characteristic of the sag mill is that the crushing ratio is large. The particle size of the materials to be ground is 300 ~ 400mm, sometimes even larger, and the minimum particle size of the materials to be discharged can reach 0.1 mm. The calculation shows that the crushing ratio can reach 3000 ~ 4000, while the ball mills crushing ratio is smaller. The feed size is usually between 20-30mm and the product size is 0-3mm.

Both the autogenous grinding mill and the ball mill feed parts are welded with groove and embedded inner wear-resistant lining plate. As the sag mill does not contain grinding medium, the abrasion and impact on the equipment are relatively small.

The feed of the ball mill contains grinding balls. In order to effectively reduce the direct impact of materials on the ball mill feed bushing and improve the service life of the ball mill feed bushing, the feeding point of the groove in the feeding part of the ball mill must be as close to the side of the mill barrel as possible. And because the ball mill feed grain size is larger, ball mill feeding groove must have a larger slope and height, so that feed smooth.

Since the power of the autogenous tumbling mill is relatively small, it is appropriate to choose dynamic and static pressure bearing. The ball bearing liner is made of lead-based bearing alloy, and the back of the bearing is formed with a waist drum to form a contact centering structure, with the advantages of flexible movement. The bearing housing is lubricated by high pressure during start-up and stop-up, and the oil film is formed by static pressure. The journal is lifted up to prevent dry friction on the sliding surface, and the starting energy moment is reduced. The bearing lining is provided with a snake-shaped cooling water pipe, which can supply cooling water when necessary to reduce the temperature of the bearing bush. The cooling water pipe is made of red copper which has certain corrosion resistance.

Ball mill power is relatively large, the appropriate choice of hydrostatic sliding bearing. The main bearing bush is lined with babbitt alloy bush, each bush has two high-pressure oil chambers, high-pressure oil has been supplied to the oil chamber before and during the operation of the mill, the high-pressure oil enters the oil chamber through the shunting motor, and the static pressure oil film is compensated automatically to ensure the same oil film thickness To provide a continuous static pressure oil film for mill operation, to ensure that the journal and the bearing Bush are completely out of contact, thus greatly reducing the mill start-up load, and can reduce the impact on the mill transmission part, but also can avoid the abrasion of the bearing Bush, the service life of the bearing Bush is prolonged. The pressure indication of the high pressure oil circuit can be used to reflect the load of the mill indirectly. When the mill stops running, the high pressure oil will float the Journal, and the Journal will stop gradually in the bush, so that the Bush will not be abraded. Each main bearing is equipped with two temperature probe, dynamic monitoring of the bearing Bush temperature, when the temperature is greater than the specified temperature value, it can automatically alarm and stop grinding. In order to compensate for the change of the mill length due to temperature, there is a gap between the hollow journal at the feeding end and the bearing Bush width, which allows the journal to move axially on the bearing Bush. The two ends of the main bearing are sealed in an annular way and filled with grease through the lubricating oil pipe to prevent the leakage of the lubricating oil and the entry of dust.

The end cover of the autogenous mill is made of steel plate and welded into one body; the structure is simple, but the rigidity and strength are low; the liner of the autogenous mill is made of high manganese steel.

The end cover and the hollow shaft can be made into an integral or split type according to the actual situation of the project. No matter the integral or split type structure, the end cover and the hollow shaft are all made of Casting After rough machining, the key parts are detected by ultrasonic, and after finishing, the surface is detected by magnetic particle. The surface of the hollow shaft journal is Polished after machining. The end cover and the cylinder body are all connected by high-strength bolts. Strict process measures to control the machining accuracy of the joint surface stop, to ensure reliable connection and the concentricity of the two end journal after final assembly. According to the actual situation of the project, the cylinder can be made as a whole or divided, with a flanged connection and stop positioning. All welds are penetration welds, and all welds are inspected by ultrasonic nondestructive testing After welding, the whole Shell is returned to the furnace for tempering stress relief treatment, and after heat treatment, the shell surface is shot-peened. The lining plate of the ball mill is usually made of alloy material.

The transmission part comprises a gear and a gear, a gear housing, a gear housing and an accessory thereof. The big gear of the transmission part of the self-grinding machine fits on the hollow shaft of the discharge material, which is smaller in size, but the seal of the gear cover is not good, and the ore slurry easily enters the hollow shaft of the discharge material, causing the hollow shaft to wear.

The big gear of the ball mill fits on the mill shell, the size is bigger, the big gear is divided into half structure, the radial and axial run-out of the big gear are controlled within the national standard, the aging treatment is up to the standard, and the stress and deformation after processing are prevented. The big gear seal adopts the radial seal and the reinforced big gear shield. It is welded and manufactured in the workshop. The geometric size is controlled, the deformation is prevented and the sealing effect is ensured. The small gear transmission device adopts the cast iron base, the bearing base and the bearing cap are processed at the same time to reduce the vibration in operation. Large and small gear lubrication: The use of spray lubrication device timing quantitative forced spray lubrication, automatic control, no manual operation. The gear cover is welded by profile steel and high-quality steel plate. In order to enhance the stiffness of the gear cover, the finite element analysis is carried out, and the supporting structure is added in the weak part according to the analysis results.

The self-mill adopts the self-return device to realize the discharge of the mill. The self-returning device is located in the revolving part of the mill, and the material forms a self-circulation in the revolving part of the mill through the self-returning device, discharging the qualified material from the mill, leading the unqualified material back into the revolving part to participate in the grinding operation.

The ball mill adopts a discharge screen similar to the ball mill, and the function of blocking the internal medium of the overflow ball mill is accomplished inside the rotary part of the ball mill. The discharge screen is only responsible for forcing out a small amount of the medium that overflows into the discharge screen through the internal welding reverse spiral, to achieve forced discharge mill.

The slow drive consists of a brake motor, a coupling, a planetary reducer and a claw-type clutch. The device is connected to a pinion shaft and is used for mill maintenance and replacement of liners. In addition, after the mill is shut down for a long time, the slow-speed transmission device before starting the main motor can eliminate the eccentric load of the steel ball, loosen the consolidation of the steel ball and materials, ensure safe start, avoid overloading of the air clutch, and play a protective role. The slow-speed transmission device can realize the point-to-point reverse in the electronic control design. When connecting the main motor drive, the claw-type Clutch automatically disengages, the maintenance personnel should pay attention to the safety.

The slow drive device of the ball mill is provided with a rack and pinion structure, and the operating handle is moved to the side away from the cylinder body The utility model not only reduces the labor intensity but also ensures the safety of the operators.

ball mills - an overview | sciencedirect topics

ball mills - an overview | sciencedirect topics

A ball mill is a type of grinder used to grind and blend bulk material into QDs/nanosize using different sized balls. The working principle is simple; impact and attrition size reduction take place as the ball drops from near the top of a rotating hollow cylindrical shell. The nanostructure size can be varied by varying the number and size of balls, the material used for the balls, the material used for the surface of the cylinder, the rotation speed, and the choice of material to be milled. Ball mills are commonly used for crushing and grinding the materials into an extremely fine form. The ball mill contains a hollow cylindrical shell that rotates about its axis. This cylinder is filled with balls that are made of stainless steel or rubber to the material contained in it. Ball mills are classified as attritor, horizontal, planetary, high energy, or shaker.

Grinding elements in ball mills travel at different velocities. Therefore, collision force, direction and kinetic energy between two or more elements vary greatly within the ball charge. Frictional wear or rubbing forces act on the particles, as well as collision energy. These forces are derived from the rotational motion of the balls and movement of particles within the mill and contact zones of colliding balls.

By rotation of the mill body, due to friction between mill wall and balls, the latter rise in the direction of rotation till a helix angle does not exceed the angle of repose, whereupon, the balls roll down. Increasing of rotation rate leads to growth of the centrifugal force and the helix angle increases, correspondingly, till the component of weight strength of balls become larger than the centrifugal force. From this moment the balls are beginning to fall down, describing during falling certain parabolic curves (Figure 2.7). With the further increase of rotation rate, the centrifugal force may become so large that balls will turn together with the mill body without falling down. The critical speed n (rpm) when the balls are attached to the wall due to centrifugation:

where Dm is the mill diameter in meters. The optimum rotational speed is usually set at 6580% of the critical speed. These data are approximate and may not be valid for metal particles that tend to agglomerate by welding.

The degree of filling the mill with balls also influences productivity of the mill and milling efficiency. With excessive filling, the rising balls collide with falling ones. Generally, filling the mill by balls must not exceed 3035% of its volume.

The mill productivity also depends on many other factors: physical-chemical properties of feed material, filling of the mill by balls and their sizes, armor surface shape, speed of rotation, milling fineness and timely moving off of ground product.

where b.ap is the apparent density of the balls; l is the degree of filling of the mill by balls; n is revolutions per minute; 1, and 2 are coefficients of efficiency of electric engine and drive, respectively.

A feature of ball mills is their high specific energy consumption; a mill filled with balls, working idle, consumes approximately as much energy as at full-scale capacity, i.e. during grinding of material. Therefore, it is most disadvantageous to use a ball mill at less than full capacity.

Grinding elements in ball mills travel at different velocities. Therefore, collision force, direction, and kinetic energy between two or more elements vary greatly within the ball charge. Frictional wear or rubbing forces act on the particles as well as collision energy. These forces are derived from the rotational motion of the balls and the movement of particles within the mill and contact zones of colliding balls.

By the rotation of the mill body, due to friction between the mill wall and balls, the latter rise in the direction of rotation until a helix angle does not exceed the angle of repose, whereupon the balls roll down. Increasing the rotation rate leads to the growth of the centrifugal force and the helix angle increases, correspondingly, until the component of the weight strength of balls becomes larger than the centrifugal force. From this moment, the balls are beginning to fall down, describing certain parabolic curves during the fall (Fig. 2.10).

With the further increase of rotation rate, the centrifugal force may become so large that balls will turn together with the mill body without falling down. The critical speed n (rpm) when the balls remain attached to the wall with the aid of centrifugal force is:

where Dm is the mill diameter in meters. The optimum rotational speed is usually set at 65%80% of the critical speed. These data are approximate and may not be valid for metal particles that tend to agglomerate by welding.

where db.max is the maximum size of the feed (mm), is the compression strength (MPa), E is the modulus of elasticity (MPa), b is the density of material of balls (kg/m3), and D is the inner diameter of the mill body (m).

The degree of filling the mill with balls also influences the productivity of the mill and milling efficiency. With excessive filling, the rising balls collide with falling ones. Generally, filling the mill by balls must not exceed 30%35% of its volume.

The productivity of ball mills depends on the drum diameter and the relation of drum diameter and length. The optimum ratio between length L and diameter D, L:D, is usually accepted in the range 1.561.64. The mill productivity also depends on many other factors, including the physical-chemical properties of the feed material, the filling of the mill by balls and their sizes, the armor surface shape, the speed of rotation, the milling fineness, and the timely moving off of the ground product.

where D is the drum diameter, L is the drum length, b.ap is the apparent density of the balls, is the degree of filling of the mill by balls, n is the revolutions per minute, and 1, and 2 are coefficients of efficiency of electric engine and drive, respectively.

A feature of ball mills is their high specific energy consumption. A mill filled with balls, working idle, consumes approximately as much energy as at full-scale capacity, that is, during the grinding of material. Therefore, it is most disadvantageous to use a ball mill at less than full capacity.

Milling time in tumbler mills is longer to accomplish the same level of blending achieved in the attrition or vibratory mill, but the overall productivity is substantially greater. Tumbler mills usually are used to pulverize or flake metals, using a grinding aid or lubricant to prevent cold welding agglomeration and to minimize oxidation [23].

Cylindrical Ball Mills differ usually in steel drum design (Fig. 2.11), which is lined inside by armor slabs that have dissimilar sizes and form a rough inside surface. Due to such juts, the impact force of falling balls is strengthened. The initial material is fed into the mill by a screw feeder located in a hollow trunnion; the ground product is discharged through the opposite hollow trunnion.

Cylindrical screen ball mills have a drum with spiral curved plates with longitudinal slits between them. The ground product passes into these slits and then through a cylindrical sieve and is discharged via the unloading funnel of the mill body.

Conical Ball Mills differ in mill body construction, which is composed of two cones and a short cylindrical part located between them (Fig. 2.12). Such a ball mill body is expedient because efficiency is appreciably increased. Peripheral velocity along the conical drum scales down in the direction from the cylindrical part to the discharge outlet; the helix angle of balls is decreased and, consequently, so is their kinetic energy. The size of the disintegrated particles also decreases as the discharge outlet is approached and the energy used decreases. In a conical mill, most big balls take up a position in the deeper, cylindrical part of the body; thus, the size of the balls scales down in the direction of the discharge outlet.

For emptying, the conical mill is installed with a slope from bearing to one. In wet grinding, emptying is realized by the decantation principle, that is, by means of unloading through one of two trunnions.

With dry grinding, these mills often work in a closed cycle. A scheme of the conical ball mill supplied with an air separator is shown in Fig. 2.13. Air is fed to the mill by means of a fan. Carried off by air currents, the product arrives at the air separator, from which the coarse particles are returned by gravity via a tube into the mill. The finished product is trapped in a cyclone while the air is returned in the fan.

The ball mill is a tumbling mill that uses steel balls as the grinding media. The length of the cylindrical shell is usually 11.5 times the shell diameter (Figure 8.11). The feed can be dry, with less than 3% moisture to minimize ball coating, or slurry containing 2040% water by weight. Ball mills are employed in either primary or secondary grinding applications. In primary applications, they receive their feed from crushers, and in secondary applications, they receive their feed from rod mills, AG mills, or SAG mills.

Ball mills are filled up to 40% with steel balls (with 3080mm diameter), which effectively grind the ore. The material that is to be ground fills the voids between the balls. The tumbling balls capture the particles in ball/ball or ball/liner events and load them to the point of fracture.

When hard pebbles rather than steel balls are used for the grinding media, the mills are known as pebble mills. As mentioned earlier, pebble mills are widely used in the North American taconite iron ore operations. Since the weight of pebbles per unit volume is 3555% of that of steel balls, and as the power input is directly proportional to the volume weight of the grinding medium, the power input and capacity of pebble mills are correspondingly lower. Thus, in a given grinding circuit, for a certain feed rate, a pebble mill would be much larger than a ball mill, with correspondingly a higher capital cost. However, the increase in capital cost is justified economically by a reduction in operating cost attributed to the elimination of steel grinding media.

In general, ball mills can be operated either wet or dry and are capable of producing products in the order of 100m. This represents reduction ratios of as great as 100. Very large tonnages can be ground with these ball mills because they are very effective material handling devices. Ball mills are rated by power rather than capacity. Today, the largest ball mill in operation is 8.53m diameter and 13.41m long with a corresponding motor power of 22MW (Toromocho, private communications).

Modern ball mills consist of two chambers separated by a diaphragm. In the first chamber the steel-alloy balls (also described as charge balls or media) are about 90mm diameter. The mill liners are designed to lift the media as the mill rotates, so the comminution process in the first chamber is dominated by crushing. In the second chamber the ball diameters are of smaller diameter, between 60 and 15mm. In this chamber the lining is typically a classifying lining which sorts the media so that ball size reduces towards the discharge end of the mill. Here, comminution takes place in the rolling point-contact zone between each charge ball. An example of a two chamber ball mill is illustrated in Fig. 2.22.15

Much of the energy consumed by a ball mill generates heat. Water is injected into the second chamber of the mill to provide evaporative cooling. Air flow through the mill is one medium for cement transport but also removes water vapour and makes some contribution to cooling.

Grinding is an energy intensive process and grinding more finely than necessary wastes energy. Cement consists of clinker, gypsum and other components mostly more easily ground than clinker. To minimise over-grinding modern ball mills are fitted with dynamic separators (otherwise described as classifiers or more simply as separators). The working principle is that cement is removed from the mill before over-grinding has taken place. The cement is then separated into a fine fraction, which meets finished product requirements, and a coarse fraction which is returned to mill inlet. Recirculation factor, that is, the ratio of mill throughput to fresh feed is up to three. Beyond this, efficiency gains are minimal.

For more than 50years vertical mills have been the mill of choice for grinding raw materials into raw meal. More recently they have become widely used for cement production. They have lower specific energy consumption than ball mills and the separator, as in raw mills, is integral with the mill body.

In the Loesche mill, Fig. 2.23,16 two pairs of rollers are used. In each pair the first, smaller diameter, roller stabilises the bed prior to grinding which takes place under the larger roller. Manufacturers use different technologies for bed stabilisation.

Comminution in ball mills and vertical mills differs fundamentally. In a ball mill, size reduction takes place by impact and attrition. In a vertical mill the bed of material is subject to such a high pressure that individual particles within the bed are fractured, even though the particles are very much smaller than the bed thickness.

Early issues with vertical mills, such as narrower PSD and modified cement hydration characteristics compared with ball mills, have been resolved. One modification has been to install a hot gas generator so the gas temperature is high enough to partially dehydrate the gypsum.

For many decades the two-compartment ball mill in closed circuit with a high-efficiency separator has been the mill of choice. In the last decade vertical mills have taken an increasing share of the cement milling market, not least because the specific power consumption of vertical mills is about 30% less than that of ball mills and for finely ground cement less still. The vertical mill has a proven track record in grinding blastfurnace slag, where it has the additional advantage of being a much more effective drier of wet feedstock than a ball mill.

The vertical mill is more complex but its installation is more compact. The relative installed capital costs tend to be site specific. Historically the installed cost has tended to be slightly higher for the vertical mill.

Special graph paper is used with lglg(1/R(x)) on the abscissa and lg(x) on the ordinate axes. The higher the value of n, the narrower the particle size distribution. The position parameter is the particle size with the highest mass density distribution, the peak of the mass density distribution curve.

Vertical mills tend to produce cement with a higher value of n. Values of n normally lie between 0.8 and 1.2, dependent particularly on cement fineness. The position parameter is, of course, lower for more finely ground cements.

Separator efficiency is defined as specific power consumption reduction of the mill open-to-closed-circuit with the actual separator, compared with specific power consumption reduction of the mill open-to-closed-circuit with an ideal separator.

As shown in Fig. 2.24, circulating factor is defined as mill mass flow, that is, fresh feed plus separator returns. The maximum power reduction arising from use of an ideal separator increases non-linearly with circulation factor and is dependent on Rf, normally based on residues in the interval 3245m. The value of the comminution index, W, is also a function of Rf. The finer the cement, the lower Rf and the greater the maximum power reduction. At C = 2 most of maximum power reduction is achieved, but beyond C = 3 there is very little further reduction.

Separator particle separation performance is assessed using the Tromp curve, a graph of percentage separator feed to rejects against particle size range. An example is shown in Fig. 2.25. Data required is the PSD of separator feed material and of rejects and finished product streams. The bypass and slope provide a measure of separator performance.

The particle size is plotted on a logarithmic scale on the ordinate axis. The percentage is plotted on the abscissa either on a linear (as shown here) or on a Gaussian scale. The advantage of using the Gaussian scale is that the two parts of the graph can be approximated by two straight lines.

The measurement of PSD of a sample of cement is carried out using laser-based methodologies. It requires a skilled operator to achieve consistent results. Agglomeration will vary dependent on whether grinding aid is used. Different laser analysis methods may not give the same results, so for comparative purposes the same method must be used.

The ball mill is a cylindrical drum (or cylindrical conical) turning around its horizontal axis. It is partially filled with grinding bodies: cast iron or steel balls, or even flint (silica) or porcelain bearings. Spaces between balls or bearings are occupied by the load to be milled.

Following drum rotation, balls or bearings rise by rolling along the cylindrical wall and descending again in a cascade or cataract from a certain height. The output is then milled between two grinding bodies.

Ball mills could operate dry or even process a water suspension (almost always for ores). Dry, it is fed through a chute or a screw through the units opening. In a wet path, a system of scoops that turn with the mill is used and it plunges into a stationary tank.

Mechanochemical synthesis involves high-energy milling techniques and is generally carried out under controlled atmospheres. Nanocomposite powders of oxide, nonoxide, and mixed oxide/nonoxide materials can be prepared using this method. The major drawbacks of this synthesis method are: (1) discrete nanoparticles in the finest size range cannot be prepared; and (2) contamination of the product by the milling media.

More or less any ceramic composite powder can be synthesized by mechanical mixing of the constituent phases. The main factors that determine the properties of the resultant nanocomposite products are the type of raw materials, purity, the particle size, size distribution, and degree of agglomeration. Maintaining purity of the powders is essential for avoiding the formation of a secondary phase during sintering. Wet ball or attrition milling techniques can be used for the synthesis of homogeneous powder mixture. Al2O3/SiC composites are widely prepared by this conventional powder mixing route by using ball milling [70]. However, the disadvantage in the milling step is that it may induce certain pollution derived from the milling media.

In this mechanical method of production of nanomaterials, which works on the principle of impact, the size reduction is achieved through the impact caused when the balls drop from the top of the chamber containing the source material.

A ball mill consists of a hollow cylindrical chamber (Fig. 6.2) which rotates about a horizontal axis, and the chamber is partially filled with small balls made of steel, tungsten carbide, zirconia, agate, alumina, or silicon nitride having diameter generally 10mm. The inner surface area of the chamber is lined with an abrasion-resistant material like manganese, steel, or rubber. The magnet, placed outside the chamber, provides the pulling force to the grinding material, and by changing the magnetic force, the milling energy can be varied as desired. The ball milling process is carried out for approximately 100150h to obtain uniform-sized fine powder. In high-energy ball milling, vacuum or a specific gaseous atmosphere is maintained inside the chamber. High-energy mills are classified into attrition ball mills, planetary ball mills, vibrating ball mills, and low-energy tumbling mills. In high-energy ball milling, formation of ceramic nano-reinforcement by in situ reaction is possible.

It is an inexpensive and easy process which enables industrial scale productivity. As grinding is done in a closed chamber, dust, or contamination from the surroundings is avoided. This technique can be used to prepare dry as well as wet nanopowders. Composition of the grinding material can be varied as desired. Even though this method has several advantages, there are some disadvantages. The major disadvantage is that the shape of the produced nanoparticles is not regular. Moreover, energy consumption is relatively high, which reduces the production efficiency. This technique is suitable for the fabrication of several nanocomposites, which include Co- and Cu-based nanomaterials, Ni-NiO nanocomposites, and nanocomposites of Ti,C [71].

Planetary ball mill was used to synthesize iron nanoparticles. The synthesized nanoparticles were subjected to the characterization studies by X-ray diffraction (XRD), and scanning electron microscopy (SEM) techniques using a SIEMENS-D5000 diffractometer and Hitachi S-4800. For the synthesis of iron nanoparticles, commercial iron powder having particles size of 10m was used. The iron powder was subjected to planetary ball milling for various period of time. The optimum time period for the synthesis of nanoparticles was observed to be 10h because after that time period, chances of contamination inclined and the particles size became almost constant so the powder was ball milled for 10h to synthesize nanoparticles [11]. Fig. 12 shows the SEM image of the iron nanoparticles.

The vibratory ball mill is another kind of high-energy ball mill that is used mainly for preparing amorphous alloys. The vials capacities in the vibratory mills are smaller (about 10 ml in volume) compared to the previous types of mills. In this mill, the charge of the powder and milling tools are agitated in three perpendicular directions (Fig. 1.6) at very high speed, as high as 1200 rpm.

Another type of the vibratory ball mill, which is used at the van der Waals-Zeeman Laboratory, consists of a stainless steel vial with a hardened steel bottom, and a single hardened steel ball of 6 cm in diameter (Fig. 1.7).

The mill is evacuated during milling to a pressure of 106 Torr, in order to avoid reactions with a gas atmosphere.[44] Subsequently, this mill is suitable for mechanical alloying of some special systems that are highly reactive with the surrounding atmosphere, such as rare earth elements.

In spite of the traditional approaches used for gas-solid reaction at relatively high temperature, Calka etal.[58] and El-Eskandarany etal.[59] proposed a solid-state approach, the so-called reactive ball milling (RBM), used for preparations different families of meal nitrides and hydrides at ambient temperature. This mechanically induced gas-solid reaction can be successfully achieved, using either high- or low-energy ball-milling methods, as shown in Fig.9.5. However, high-energy ball mill is an efficient process for synthesizing nanocrystalline MgH2 powders using RBM technique, it may be difficult to scale up for matching the mass production required by industrial sector. Therefore, from a practical point of view, high-capacity low-energy milling, which can be easily scaled-up to produce large amount of MgH2 fine powders, may be more suitable for industrial mass production.

In both approaches but with different scale of time and milling efficiency, the starting Mg metal powders milled under hydrogen gas atmosphere are practicing to dramatic lattice imperfections such as twinning and dislocations. These defects are caused by plastics deformation coupled with shear and impact forces generated by the ball-milling media.[60] The powders are, therefore, disintegrated into smaller particles with large surface area, where very clean or fresh oxygen-free active surfaces of the powders are created. Moreover, these defects, which are intensively located at the grain boundaries, lead to separate micro-scaled Mg grains into finer grains capable to getter hydrogen by the first atomically clean surfaces to form MgH2 nanopowders.

Fig.9.5 illustrates common lab scale procedure for preparing MgH2 powders, starting from pure Mg powders, using RBM via (1) high-energy and (2) low-energy ball milling. The starting material can be Mg-rods, in which they are processed via sever plastic deformation,[61] using for example cold-rolling approach,[62] as illustrated in Fig.9.5. The heavily deformed Mg-rods obtained after certain cold rolling passes can be snipped into small chips and then ball-milled under hydrogen gas to produce MgH2 powders.[8]

Planetary ball mills are the most popular mills used in scientific research for synthesizing MgH2 nanopowders. In this type of mill, the ball-milling media have considerably high energy, because milling stock and balls come off the inner wall of the vial and the effective centrifugal force reaches up to 20 times gravitational acceleration. The centrifugal forces caused by the rotation of the supporting disc and autonomous turning of the vial act on the milling charge (balls and powders). Since the turning directions of the supporting disc and the vial are opposite, the centrifugal forces alternately are synchronized and opposite. Therefore, the milling media and the charged powders alternatively roll on the inner wall of the vial, and are lifted and thrown off across the bowl at high speed.

In the typical experimental procedure, a certain amount of the Mg (usually in the range between 3 and 10g based on the vials volume) is balanced inside an inert gas atmosphere (argon or helium) in a glove box and sealed together with certain number of balls (e.g., 2050 hardened steel balls) into a hardened steel vial (Fig.9.5A and B), using, for example, a gas-temperature-monitoring system (GST). With the GST system, it becomes possible to monitor the progress of the gas-solid reaction taking place during the RBM process, as shown in Fig.9.5C and D. The temperature and pressure changes in the system during milling can be also used to realize the completion of the reaction and the expected end product during the different stages of milling (Fig.9.5D). The ball-to-powder weight ratio is usually selected to be in the range between 10:1 and 50:1. The vial is then evacuated to the level of 103bar before introducing H2 gas to fill the vial with a pressure of 550bar (Fig.9.5B). The milling process is started by mounting the vial on a high-energy ball mill operated at ambient temperature (Fig.9.5C).

Tumbling mill is cylindrical shell (Fig.9.6AC) that rotates about a horizontal axis (Fig.9.6D). Hydrogen gas is pressurized into the vial (Fig.9.6C) together with Mg powders and ball-milling media, using ball-to-powder weight ratio in the range between 30:1 and 100:1. Mg powder particles meet the abrasive and impacting force (Fig.9.6E), which reduce the particle size and create fresh-powder surfaces (Fig.9.6F) ready to react with hydrogen milling atmosphere.

Figure 9.6. Photographs taken from KISR-EBRC/NAM Lab, Kuwait, show (A) the vial and milling media (balls) and (B) the setup performed to charge the vial with 50bar of hydrogen gas. The photograph in (C) presents the complete setup of GST (supplied by Evico-magnetic, Germany) system prior to start the RBM experiment for preparing of MgH2 powders, using Planetary Ball Mill P400 (provided by Retsch, Germany). GST system allows us to monitor the progress of RBM process, as indexed by temperature and pressure versus milling time (D).

The useful kinetic energy in tumbling mill can be applied to the Mg powder particles (Fig.9.7E) by the following means: (1) collision between the balls and the powders; (2) pressure loading of powders pinned between milling media or between the milling media and the liner; (3) impact of the falling milling media; (4) shear and abrasion caused by dragging of particles between moving milling media; and (5) shock-wave transmitted through crop load by falling milling media. One advantage of this type of mill is that large amount of the powders (100500g or more based on the mill capacity) can be fabricated for each milling run. Thus, it is suitable for pilot and/or industrial scale of MgH2 production. In addition, low-energy ball mill produces homogeneous and uniform powders when compared with the high-energy ball mill. Furthermore, such tumbling mills are cheaper than high-energy mills and operated simply with low-maintenance requirements. However, this kind of low-energy mill requires long-term milling time (more than 300h) to complete the gas-solid reaction and to obtain nanocrystalline MgH2 powders.

Figure 9.7. Photos taken from KISR-EBRC/NAM Lab, Kuwait, display setup of a lab-scale roller mill (1000m in volume) showing (A) the milling tools including the balls (milling media and vial), (B) charging Mg powders in the vial inside inert gas atmosphere glove box, (C) evacuation setup and pressurizing hydrogen gas in the vial, and (D) ball milling processed, using a roller mill. Schematic presentations show the ball positions and movement inside the vial of a tumbler mall mill at a dynamic mode is shown in (E), where a typical ball-powder-ball collusion for a low energy tumbling ball mill is presented in (F).

amateur rocketry motor (engine) propellant

amateur rocketry motor (engine) propellant

There is quite a number of propellants used in experimental rocketry and often people will get attached to one type or another and become quite knowledgeable about that propellant. The three most common types of propellants are compressed powder, usually black powder, sugar propellant (most commonly sucrose, dextrose and most recently, sorbitol) and composite propellant using ammonium nitrate or ammonium perchlorate as the oxidizer and a powdered metal (usually aluminum or magnesium) as the fuel). There are three well known people who are "experts" in each of these propellants: David Sleeter (Teleflite Corporation) has a book on black powder motors "Amateur Rocket Motor Construction." John Wickman has a book "How to Make Amateur Rockets" and his propellant of choice is composite propellant. Richard Nakka is the sugar rocket specialist and has the most comprehensive experimental rocketry website bar none.

Note: You will see the term "grain" used throughout this website. In black powders and smokeless powders, the grain size refers to the size of each particle of powder which is quite small, on the order of 1/16". In rocketry, the propellant is compressed or cast into large forms just smaller than the motor diameter. A motor may use one to as high as seven or more grains in a motor or the propellant may be cast directly into the motor (case bonded grains) in which case the entire mass of propellant is referred to as the grain.

Compressed propellant is prepared dry but may be wet at some stage of the preparation. It is loaded into the motor casing by compressing with constant mechanical or hydraulic pressure or by impact such as by blows of a mallet or hammer. The burn rate depends on how fine the components are ground, how intimately it is mixed, and the density which is determined by how much it is compressed. Compressed propellants are normally loaded into wound paper tubing which has a lower burst strength than PVC or metal. An amateur will normally use blows to compress the propellant and this means the amount of compression can vary and so getting a consistent rocket motor becomes difficult and can result in burst motors or motors with lower thrust. This is why I switched to cast sugar propellant. It is also easy to split the casing because the hammer blows can create tremendous hydraulic pressure on the casing. The normal way to avoid this is to use an external clamp around the entire outside of the case. A series of hose clamps can be used but this takes a fair amount of time to put them all on and take them all off. I used a wood clamp that you can see in my free manual. David Sleeter uses a fabricated steel clamp but a lot of people don't have the tools to do that.

In the early days of experimental rocketry powdered zinc and sulfur were a common propellant.This was also referred as "micrograin." The optimum mixture was 2.04 parts zinc to one part sulfur by weight. Its burn rate depends on how small the particle size is for each and how much it is compressed. The more dense it is compacted, the slower the burn rate. It's burn rate is between 14 and 290 inches per second. At 160 lbs/ft3 and 1000 psi, the following has been measured*:

Because it is so difficult to compress the powder to a known value consistently, rocket motors made with this formula typically either don't have much power and may not get off the launch pad, or they blow up from over pressurization. It is not used by any serious rocketeers today.

Black powder is made from Potassium Nitrate (KNO3), Charcoal and Sulfur. The common ratio is 75:15:10. Like zinc-sulfur, the burn rate depends on the particle size and how much it is compressed. Black powder can be used used as a propellant with more consistency than zinc-sulfur and is the propellant used in small commercial model rocket engines. My 1979 manual explains how to make and use black powder for rocket engines. David Sleeter took the development to the next level and published his book, Amateur Rocket Motor Construction. The burn rate of black powder can be slowed by the addition of other components. I used calcium carbonate. David uses baking soda. David also varies the type of charcoal used to get different burn rates and to control chuffing. He adds Red gum as a binder (I used Gum Acacia) and either water, alcohol, or acetone is added before loading so the powder will compress more. I did the same but also loaded it dry with good results.

Black powder, regardless of how fine it is ground, in the initial dry mix state is not very powerful. It must be mixed with a little water until it is a darker color and then dried again. While it is wet, it can be pushed through a window screen to form grains. This grain powder is extremely fast burning. Or it can be again ground up to a powder and then it is still very fast burning. It is likely that the wetting dissolves the KNO3 and then coats it around the charcoal and sulfur particles so that it is in much more intimate contact with them. Richard Nakka notes that sulfur is only used in conventional black powder so it will ignite more easily from a spark such as is used in flintlock guns. He makes black powder from 80% potassium nitrate and 20% charcoal by weight for one of his igniters and presumably, this would also apply for black powder motors but I have not tried this yet.

Sugar and potassium nitrate are the ingredients for the common "caramel candy" propellant. Normally it is heated to a thick slurry but it also can be just mixed together dry and then compressed in a motor tube in the same way as black powder. As with all compressed propellants, the particle size of the constituents and the degree of compaction is what determines the burn rate and efficiency of the propellant and so it is difficult to get a consistent product. Mixed in this way, it also is not as powerful as when it is mixed more intimately through melting or dissolving in water and then heating. The ratio is the same as for the melted variety: 65% potassium nitrate, 35% sugar. See the Carmel Candy Propellant page for more information on the melted method of preparing this propellant.

There is some variation in the definition of composite propellant. It generally is considered to be a propellant where the oxidizer and the fuel (reducing agent) are intimately mixed together with a binder. Some define the composite propellant as being a rubber-like consistency and then the binder is that which gives that property. However, asphalt was an early binder and the finished product was not very elastic. Many also consider epoxy propellants to be classed as a composite and although it is tough rather than brittle, it definitely is not elastic. The other problem with the definition is that the binder is also a fuel. It can serve as the only fuel in the propellant, the main fuel with smaller amounts of other fuel, or another substance may be the main fuel with the binder being a lesser contributor. During the developmental years, some propellants such as those using synthetic rubbers were cast at elevated temperatures where they were liquid and then became solid when they cooled. Others, essentially all propellants for amateur rockets and many for commercial rockets, now are liquid at room temperature and a curing agent is added which reacts chemically with the binder to cause it to harden over a period of time, usually minutes to a few hours. Other substances that can be added are plasticizers and burn rate modifiers. A plasticizer can be added to some to decrease the viscosity (make it thinner) so that the propellant pours easier and makes the casting process easier. Iron oxide can be added in small amounts to increase the burn rate and there are other chemicals that could be added to slow it down (not common). There are several types of iron oxide, different chemical formulas, with varying amounts of iron and oxygen. For example, ferric oxide (Fe2O3) is red, ferrous oxide (FeO) is black, and ferrous ferric oxide (Fe3O4) is green.

This type of propellant solves one of the biggest problems of other propellant types and that is brittleness. Any propellant that is brittle can crack and that invariable causes over pressurization of the motor due to increased burn area and catastrophic failure. Cracks can occur not only from rough handling but also from the high pressure, thermal stress, and g-forces experienced in flight. The bigger the grain size, the more potential for cracks.

Virtually all motors for amateur use and most composite propellants for commercial or military rockets use Ammonium Perchlorate as the oxidizer. The oxidizer comprises 50% to 80% of the total by weight. The fuel is usually a powdered metal, either Aluminum or Magnesium. The particle size of the oxidizer and the powdered metal will make a difference in the burn rate, the smaller the size, the faster the burn rate. These propellants are harder to ignite than black powder or sugar based propellants and require a longer burning, more intense igniter.

Grinding is done to reduce the chemicals to a very small particle size. This is required for any compressed powder motors and for dry melting (melting the mixture without water.) You can grind the chemicals separately or you can grind them together IN CERTAIN SITUATIONS. If grinding together, there must be no metal involved in the operation so there can be no sparks and the heat generated must be very low. Otherwise, you could ignite the powder. All propellants that are mixed together dry are very flammable. A ball mill with non-metallic "balls" is the only acceptable method and even then, precautions must be taken in case of ignition. The dust inside can be explosive.

A small amount can be done with a mortar and pestle but a person usually is looking for an alternative pretty quickly. It can still be a good way when experimenting with different formulas because it can be washed out quickly and easily in preparation for the next chemical. This is also a good method for preparing mixtures for igniters which don't use much for each one.

You will probably read on many web sites that a blender is not a good method of grinding chemicals. One reason is that it is harder to clean and you have to make sure that there is no residue from a previous different chemical before grinding the next. Also, a blender doesn't work that well with solids. Nevertheless, it is a possibility and can be used. Sometimes you have to keep pushing the chemical into the blades because it tends to stack up and stick to the sides of the container. Be aware that you can quickly dull the blades so don't use the kitchen blender. Get one from a thrift store and dedicate it to your own project.

When I first started experimenting with black powder motors thirty years ago, I used potassium nitrate and sulfur from the drugstore. I ground up charcoal briquettes for the charcoal. There are binders in charcoal that make it a poor source and that is probably why I found that a formula of 68% KNO3, 20% charcoal, and 12% sulfur worked best for my chemicals rather than the normal 75%, 15% 10%. I needed more charcoal to make it work because of the impurities. I broke up the briquettes inside the leg of an old pair of jeans with a hammer first, then poured some of that into a blender and ground it up more. Finally, I sifted that through some silk that I had used for model airplanes that had a very tight weave (better than through nylons). It was a difficult, messy and time consuming process but it resulted in a powder as fine as purchased air floated charcoal. I recommend not wasting your time this way and just buying your chemicals.

A coffee mill does a job similar to a blender but it works a little better. You can grind a little at a time but it does a better job of keeping the material pulled into the blades. It was designed to grind solids so it is a better choice. A new coffee mill (a cheap one) can be purchased for about $15. It has the same problem of cleaning but with its low price, a person could have more than one if he needed to grind more than one ingredient. It is also a little faster, even though you can only grind a little at a time, you can do it quickly and get a sizeable amount of ground chemicals in a reasonable time through multiple batches. Check for lumps that haven't been reduced to powder in both a blender and a coffee mill before using. You might want to put it through a fine screen to insure you don't have lumps.

The ball mill is the best way to grind and you can also grind all the ingredients for black powder together. A ball mill is really a rock tumbler. The rock tumbler is usually made of hard rubber at least on the inside. Mine has an aluminum plate inside the rubber lid to help give it rigidity but when it is closed up, there is no exposed metal. When polishing rocks, the tumbler is filled about three quarter full of rocks, then water and the abrasive is added to that. When grinding chemicals or powder, a similar process is used except there is no water added. David Sleeter in his book prescribed brass bar stock. I checked into that and when I saw the price, I decided there IS another way. I tried some rocks (after all, it really is a ROCK tumbler). I used those for milling potassium nitrate. That worked fine so I also used the rocks to mill charcoal (after washing them). That also worked fine. I still had a little concern about using the rocks to grind black powder with all the ingredients (explosive) because some rocks can still produce sparks, though unlikely. Since I had already rejected brass bar stock, I thought about glass marbles. They are cheap, round, totally spark free. They worked GREAT creating dust consistency for everything I tried in it--charcoal, potassium nitrate and black powder.

There is one driven rubber roller attached to the large pulley. There is a small pulley on the motor. It is a double reduction system. The drum actually turns at about 2 rpm. The drum has a grooved plastic nut. The groove runs in the slot at the top of the white angle bracket to keep it from moving along the roller axis and off the machine.

The drum is all rubber and as can be seen has multiple flat sides. This helps the contents to tumble rather than roll. The white residue is KNO3 residue left from my last milled batch which was milled to a talc like powder using 400 standard size glass marbles that I got at a Dollar Store for 100 for $1.00. This has a capacity of 1-1/4 gallons and will mill about two pounds in a batch. Starting with lumps about half the size of the marbles and smaller, it takes about six or eight hours to mill to dust.

The lid is composed of four parts as can be seen in the left picture: the inner lid, the outer lid, a washer and plastic grooved nut. The inner lid is rubber with an aluminum disk molded into it for stiffness. The bottom or rubber side of the inner lid can be seen in the picture on the right. The inner lid fits snuggly inside the drum and provides an entirely rubber milling area and also is water tight. (Rock tumbling is done with water, an abrasive and the rocks). When the outer lid is placed on, it helps snug the drum up against the inner lid.

This method is mainly used for black powder. Whatever components are not already in a fine powder need to first be ground. Usually the sulfur is already a powder, at least if you have "flours of sulfur" or "sulfur flour" or something similar. If you are making your own charcoal from chunks, then it will need to be broken up into small pieces first and then milled to a fine powder. "Air floated" charcoal can be purchased and that doesn't need to be milled at all. Finally, the potassium nitrate is probably not a fine powder and will probably need to be milled. The individual components are usually first milled separately. The mill needs to be thoroughly washed between uses of different chemicals. Then the right proportions of each are milled together. Last, the powder is mixed with just enough water (alcohol or acetone can be used because they dry faster) to moisten the whole batch and if it is to be used in a rocket motor, it can then be loaded directly and rammed in place by blows with a mallet on a rod in the paper rocket tube. It can also be let dry first and then re-ground and loaded dry. See the 1979 manual for details (pay attention to it's revision)

As mentioned above, the same formula for melted caramel candy propellant can be milled separately then mixed together and loaded dry into a paper motor tube in the same way as black powder. It is difficult to get these to be consistent and they don't have as much total power (specific impulse) as using the heated method.

This is the third type of compressed propellant but is not considered a dependable fuel now since there is so much information and chemicals available for other fuels. The method would be the same as for Sugar and KN. The Zinc would have to be purchased already in a powdered state since it can't be milled. It would then be dry mixed and compressed with hammer blows on a dowel.

This method takes in all other propellant types that have at least one non-liquid component and includes especially composite propellant and Epoxy propellant. These are just mixed together thoroughly and then a hardener is added which will cause the liquid slurry to harden over a short period of time, usually half an hour to several hours.

ball mill for sale | grinding machine - jxsc mining

ball mill for sale | grinding machine - jxsc mining

Ball mill is the key equipment for grinding materials. those grinding mills are widely used in the mining process, and it has a wide range of usage in grinding mineral or material into fine powder, such as gold, ironzinc ore, copper, etc.

JXSC Mining produce reliable effective ball mill for long life and minimum maintenance, incorporate many of the qualities which have made us being professional in the mineral processing industry since 1985. Various types of ball mill designs are available to suit different applications. These could include but not be restricted to coal mining grate discharge, dry type grinding, wet mineral grinding, high-temperature milling operations, stone & pebble milling.

A ball mill grinds ores to an end product size of thirty-five mesh or finer. The feeding material to a ball mill is treated by: Single or multistage crushing and screening Crushing, screening, and/or rod milling Primary crushing and autogenous/semi-autogenous grinding.

Normal feed sizes: eighty percent of six millimeters or finer for hard rocker eighty percent of twenty-five millimeters or finer for fragile rocks (Larger feed sizes can be tolerated depending on the requirements).

The ratio of machine length to the cylinder diameter of cylindrical type ball mills range from one to three through three to one. When the length to diameter ratio is two to one or even bigger, we should better choose the mill of a Tube Mill.

Grinding circuit design Grinding circuit design is available, we experienced engineers expect the chance to help you with ore material grinding mill plant of grinding circuit design, installation, operation, and optimization. The automatic operation has the advantage of saving energy consumption, grinding media, and reducing body liner wear while increasing grinding capacity. In addition, by using a software system to control the ore grinding process meet the requirements of different ore milling task.

The ball mill is a typical material grinder machine which widely used in the mineral processing plant, ball mill performs well in different material conditions either wet type grinding or dry type, and to grind the ores to a fine size.

Main ball mill components: cylinder, motor drive, grinding medium, shaft. The cylinder cavity is partial filling with the material to be ground and the metal grinding balls. When the large cylinder rotating and creating centrifugal force, the inner metal grinding mediums will be lifted to the predetermined height and then fall, the rock material will be ground under the gravity force and squeeze force of moving mediums. Feed material to be ground enters the cylinder through a hopper feeder on one end and after being crushed by the grinding medium is discharged at the other end.

Mining Equipment Manufacturers, Our Main Products: Gold Trommel, Gold Wash Plant, Dense Media Separation System, CIP, CIL, Ball Mill, Trommel Scrubber, Shaker Table, Jig Concentrator, Spiral Separator, Slurry Pump, Trommel Screen.

defense capabilities

defense capabilities

MAST prides itself on the ability to provide premium technology at competitive prices throughout the marketplace. With a spacious elastomer processing suite and full-scale production capabilities, MAST has substantial lab scale development space to rapidly prototype a variety of products.

MAST Technologies has a versatile coatings and applications sector for mixing and applying liquid coatings via spray and dip processes. MASTs automated pneumatic spray booth provides optimized and repeatable coating application to a variety of products.

Industry standard microwave measurements can be performed in-house and digital data capture allows for rapid and professional reporting. MASTs vector network analyzer provides phase and amplitude measurements in a variety of test setups, including microstrip testing, Bistatic Arch Reflectivity, and Insertion Tunnel testing.

Please see Tech Bulletin 101 for more information on the NRL Arch Reflectivity test setup. Surface and volume resistivity measurements of conductive or resistive products are provided by a surface resistivity probe and proper multimeter setup.

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