what's the difference between ball mills and rod mills - jxsc machine

what's the difference between ball mills and rod mills - jxsc machine

Both the ball mill and the rod mill are designed for grinding materials, but the same as the role of grinding materials and cylinder shape, whats the difference between ball mills and rod mills? Next, we will introduce the intrinsic properties and construction of the ball mill and the rod mill. Ball mill details

Compared with the ball mill, the rod mill adopts advanced controllable feeding and discharging technology, and can use the appropriate grinding body according to the grinding material. The point contact of the traditional ball mill can be changed into line contact, which can make the discharge granularity more uniform and the output is higher.

The rod mill is mainly used for gravity separation or magnetic separation of tungsten-tin ore and other rare metal ores, because the use of a rod mill can prevent the occurrence of dust pollution caused by excessive pulverization and improve the recovery rate of the sorting operation.

How Much the Gold Ore Ball Mill? The ball mill is suitable for grinding various ores and other materials, including mineral processing, building materials and chemical industries. The feed both can be dry and wet.

The finesse of the material milled by the ball mill is 0.074mm-0.4mm, only except for the two small ball mills that have a wider range of 0.075-0.89mm. However, the rod mill fine grinding fineness is about 0.833-0.147mm. In terms of the fineness of the ground material, the ball mill has a finer handling ability.

Can the Ball Mill Grind the Material to 325 Mesh? On the other hand, the surface area of the steel rod medium in the rod mill is smaller than that of the steel ball medium in the ball mill, so the utilization factor is lower than that of the ball mill of the same processing capacity. Rod mills are often used in coarse grinding operations and are not suitable for fine crushing. Buti in some cases, the rod mill can replace the fine crusher and solve the problem that the discharge port of the fine crusher is easy to block.

The rod mill adopts overflow type and open type discharge, does not use grate type discharge. The diameter of the rod mill discharge end is larger than that of the same size ball mill. When the rod mill speed is lower than the working speed of the same size ball mill, the medium in the rod mill is in a sloping working state. For the ball mill, depending on the specific requirements, you can choose the overflow type and grate type of discharge method.

Thats my great honor if the above comparison between the ball mill and the rod mill can help you to choose the equipment that suits your production needs. In summary, if you have high requirements on the fineness of the material, it is recommended that you choose a ball mill for processing. Because it uses a steel ball to grind more thoroughly, more contact areas, will make the fineness of the finished product higher. How to select a ball mill? we are here to help.

wet ball milling vs dry ball milling | orbis machinery, llc

wet ball milling vs dry ball milling | orbis machinery, llc

Everything we make use of in our day to day activities passes through a milling process. Cement used in building, the cereals we eat, toiletries, paints used in making our house presentable, and the tiles that beautifies the house we live in, all went through a milling process. A ball mill is a grinder which is used to grind, blend and mix materials like chemicals, ores, pyrotechnics, paints, mineral dressing process, paint and ceramic raw materials. Its working principle is impact and attrition. Ball milling have proved to be effective in increasing solid-state chemical reactivity and production of amorphous materials. Milling operations are carried out either wet or dry.

Power The difference between the result gotten from using wet and dry milling are most of the time very large. This difference is attributed to the power. The power to drive a wet ball mill is said to be 30% lesser than that of a similar dry ball mill.

Nature Of Materials In the production of some products both wet ball and dry ball milling processes are required. The grinding of the raw mix in a cement plant, can be carried out either wet or dry but because of the nature of the cement can, grinding it has to be carried out dry.

Quality The quality expected will be the determinant of which ball milling process to be used. For example, if pyrotechnic materials is grounded dry, it gives a product superior characteristics compared to the one which was grounded wet. The grinding of aluminium for the preparation of paint is most of the time carried out using a wet milling process since the method introduces stearic acid, or other antiflocculent

Environment The advantages Wet ball milling has over dry milling are higher energy efficiency, lower magnitude of excess enthalpy, better heat dissipation and absence of dust formation because of the aqueous environment it is being performed.

Introduction Of Active Surface Media Wet ball milling allows easy introduction of surface active media having to do with the reduction of the required energy for the inhibition of aggregation of fine particles. Due to wide adoption, it is only theoretically possible to introduce such material or substance in gaseous or vapour form into dry ball milling. The only practicable method of introducing substance in gaseous form is wet ball milling.

Cost In the production of ethanol, wet ball milling is the process used, because of its versatile process. It produces more products than dry ball milling, but in terms of efficiency, capital, and operating cost, most ethanol plants in the USA prefer to use dry ball milling process. In other words, dry ball milling is cost efficient in ethanol production than wet ball milling. With the above, you should be able to weigh which of the ball milling process is appropriate and cost efficient for your production needs.

cnc end mill comparison guide | matterhackers

cnc end mill comparison guide | matterhackers

There are many different factors that go into the objects you can create with a CNC mill, but the biggest contributor is going to be your end mills. At the most basic level, end mills are like drill bits but instead of only drilling vertically, they can also cut horizontally and have several form factors to get the cleanest cut for specific materials. Some are used only for plastics to keep from heating too much, some are designed to keep wood from chipping or tearing out, and some are designed for ultra fine detail work. With all the different specifications you can find with end mills, explaining each part individually would better serve your understanding, so my goal today is for you to have the considerations necessary to lead you down the path to success. Lets get started!

From one end mill to the next, the most obvious difference you will find is that end mills come in many shapes and sizes. Some are thin and pointy, and others are wide and rounded. Some of the most common shapes you will find are fishtail (or flat), ball-nosed, and bullnose, and each of these can be a straight cut or a tapered cut.

Size is the biggest determination of what you can do with any given end mill. Large ones excel at grinding through a lot of material at once, but you dont get a lot of detail out of your parts. With CNC milling, the radius of your end mill is the radius of any internal corner, so you will almost never have a perfectly square corner on the inside of a milled object. Smaller and smaller end mills can be used for each pass to clean up an edge and get the part to the final dimension and shape. However, the smaller your end mill, the more fragile it gets, so if you try to cut through material too fast with a 1/16 end mill and youre snapping it off into the workpiece. In most cases the most efficient use of a tool is to cut at around half of the diameter of the tool; with a tool, have a maximum depth of .

There are generally two forms of end mills: straight and tapered. This is a choice based on the geometry of your finished part because a tapered end mill wont be able to do all the same things as a straight end mill, and a straight end mill may not be the most efficient choice. By using a tapered end mill, the cross sectional area is larger than a straight end mill of the same tip diameter, creating a much stronger end mill that is less likely to bend while milling. For perfectly vertical walls you will need to use a straight end mill as the taper just wont reach. However for angled walls, using a straight end mill is not the most efficient, ideal choice.

Fishtail end mills are generally used to cut simple profiles out of a medium, like big letters out of a piece of wood. They cut best using the side of the mill, so most cutting software will slowly ramp the end mill down into the material, rather than a simple plunge. With fishtail end mills, you will have nice square corners at the bottom of any inset section of geometry and a smooth, flat surface anywhere it passes over the top of.

Ball-nose end mills have a dome-shaped tip. These excel at high-detail contours like relief artwork or mold and die making, but have what is known as scalloping. Since the tip of the end mill is round, having a perfectly flat surface is a challenging feat and will take many more passes than a simple fishtail to smooth out.

Bull-nose end mills are often called corner radius end mills, and are a combination of fishtail and ball-nose. These have a flat bottom, but rounded corners, so you can have a filleted inner corner while also avoiding the problem of scalloping. These are commonly used to mill molds as you dont need to use nearly as many tool changes to get flat bottom pockets and rounded contours.

The tip profile isnt the only thing that differentiates end mills. The spiral channels on an end mill - called flutes - determine which materials you can cut. Generally, less flutes equals better chip clearing at the expense of surface finish. More flutes gives you a nicer surface finish, but worse chip clearing. The softer and gummier the material, the quicker you need to remove the chips away from your part. Using a 6 flute end mill on plastic is going to melt the material more than it cuts it, and if you use it on aluminum you run the risk of generating enough heat to friction weld the aluminum to your end mill, completely ruining both pieces. The guideline for soft metals, plastic, and woods is to use one or two flutes; for high-detail milling use three or four flutes, and for carbon fiber, six or more flutes.

If you're a newcomer to the CNC milling, try starting with a two-flute, up-cut end mill and see how that works for you and your material. Considering that the material options for desktop CNC milling aren't too crazy, you can mill most of the different materials these machines are capable of using a two-flute end mill, but you will need to adjust feedrate and spindle speed.

End mills are made of a few different materials, but high-speed steel (HSS) and tungsten carbide are two of the most common. The HSS tools are more forgiving than carbide, as carbide is brittle and can chatter and shatter. HSS is also cheaper than carbide, but it tends to dull faster than carbide. In order to improve tool performance, manufacturers apply different coatings to extend the life of the tool and keep it sharp longer.

Finding the right end mill for the job is all about finding the balance between the different factors that make up the tool. Dont forget that standard procedure for CNC milling is swapping out your tools depending on which step of the process you are working on. Its perfectly normal to have dozens of tools - end mills, drill bits, engraving bits, and others - that you rotate through to get a progressively closer shape and finish to your final product. I hope that Ive either gotten you interested in using more end mills or at least given you a better understanding of how once differs from the next.

what are the differences between ball mill and rod mill? | fote machinery

what are the differences between ball mill and rod mill? | fote machinery

Ball mill and rod mill are the common grinding equipment applied in the grinding process. They are similar in appearance and both of them are horizontal cylindrical structures. Their cylinders are equipped with grinding medium, feeder, gears, and transmission device.

The working principle of ball mill and rod mill machine is similar, too. That is, the cylinder drives the movement of the grinding medium (lifting the grinding medium to a certain height then dropping). Under the action of centrifugal force and friction, the material is impacted and ground to required size, so as to realize the operation of mineral grinding.

Grate discharge ball mill can discharge material through sieve plate, with the advantage of the low height of the discharge port which can make the material pass quickly so tha t to avoid over-grinding of material. Under the same condition, it has a higher capacity and can save more energy than other types of mills;

It is better to choose a grate discharge ball mill when the required discharge size is in the range of 0.2 to 0.3 mm. Grate discharge ball mill is usually applied in the first grinding system because it can discharge the qualified product immediately.

Overflow discharge ball mill can grind ores into the size under 0.2 mm, so it is very suitable for the second grinding system. The capacity of it is about 15% lower than grate discharge ball mill in the same specification, and the loaded grinding medium is also less than that one.

It can be divided into three types of rod mills according to the discharge methods, center and side discharge rod mill, end and side discharge rod mill and shaft neck overflow discharge rod mill.

It is fed through the shaft necks in the two ends of rod mill, and discharges ore pulp through the port in the center of the cylinder. Center and side discharge rod mill can grind ores coarsely because of its structure.

This kind of rod mill can be used for wet grinding and dry grinding. "A rod mill is recommended if we want to properly grind large grains, because the ball mill will not attack them as well as rod mills will."

It is fed through one end of the shaft neck, and with the help of several circular holes, the ore pulp is discharged to the next ring groove. The rod mill is mainly used for dry and wet grinding processes that require the production of medium-sized products.

The diameter of the shaft neck is larger than the diameter of the feeding port about 10 to 20 centimeters, so that the height difference can form a gradient for ore pulp flow. There is equipped with a spiral screen in the discharge shaft neck to remove the impurities.

It has high toughness, good manufacturability and low price. The surface layer of high manganese steel will harden rapidly under the action of great impact or contact. The harder index is five to seven times higher than other materials, and the wear resistance is greatly improved.

It has high toughness, good manufacturability and low price. The surface layer of high manganese steel will harden rapidly under the action of great impact or contact. The harder index is five to seven times higher than other materials, and the wear resistance is greatly improved.

It is made of several elements such as chromium and molybdenum, which has high hardness and good toughness. Under the same work condition, the service of this kind of ball is one time longer than the high manganese steel ball.

After the professional technology straightening and quenching processing process, a high carbon steel rod has high hardness, excellent performance, good wear resistance and outstanding quality.

The steel ball of ball mill and the mineral material are in point contact, so the finished product has a high degree of fineness, but it is also prone to over-grinding. Therefore, it is suitable for the production with high material fineness and is not suitable for the gravity beneficiation of metal ores.

The steel rod and the material are in line or surface contact, and most of the coarse particles are first crushed and then ground. Therefore, the finished product is uniform in quality, excellent in particle size, and high in qualification rate.

The cylinder shape of the rod mill and the ball mill is different: the cylinder of the rod mill is a long type, and the floor area is large. The ratio of the length to the diameter of the cylinder is generally 1.5 to 2.0;

The cylinder of the ball mill is a barrel or a cone. And the ratio of the length to the diameter of the cylinder is small, and in most cases the ratio is only slightly larger than 1, and the floor area is small, too.

The above is the main content of this article. The ball mill and the rod mill are the same type of machine on the appearance, but there are still great differences in the interior. It is very necessary to select a suitable machine for the production to optimize the product effect and maximize its efficiency.

As a leading mining machinery manufacturer and exporter in China, we are always here to provide you with high quality products and better services. Welcome to contact us through one of the following ways or visit our company and factories.

Based on the high quality and complete after-sales service, our products have been exported to more than 120 countries and regions. Fote Machinery has been the choice of more than 200,000 customers.

whats the difference of ball mill, sag mill, ag mill?

whats the difference of ball mill, sag mill, ag mill?

Attrition mill is a type of grinding mill by kinds of media to crush lump to powder-like substances. The impact can be rock on rock such as in an Autogenous Grinding (AG) mill, rock and a small ball charge (~10%), used in Semi Autogenous Grinding (SAG) mills, balls of various sizes in Ball Mills and less commonly these days, steel rods in Rod Mills.

These machines are used to grind or mix metals or raw materials for further processing. Various materials are placed into the mill drum and rotated with the mined materials that are to be crushed. The ball mill contains materials meant for crushing and grinding, such as balls of ceramic, small rocks, or balls made from stainless steel. The internal device of the ball mill grinds material into powder-like substances, and can rotate continuously for optimal grinding and refinery production.

A Sag mill is most often used in the mining fields, particularly in the mining of precious metals such as gold, copper, silver, and nickel. The sag mill serves in the line of industrial mining equipment designed to process, crush, separate, or locate precious metals from mined coal. The Sag mill is one of the large mining equipment pieces, and often requires mining equipment repair and maintenance. This is most often due to the large amount of heavy, residue bearing material being churned through the large drums of the grind mill. The Sag mill uses lifting plates along the interior of the drum, which lift material throughout the rotations, causing them to fall onto one another to promote crushing.

A ball mill has many steel or porcelain balls put in a drum to grind the feed between balls and between the balls and drum inner wall as the drum rotates. This mill is capable of grinding lumps whose size is tens of millimeters into a product tens of microns or even several microns. The ball mill can grind various ores and other materials with dry type and wet type. There are two kinds of ball mill, grate type and overfall type due to different ways of discharging material.

differences between ball mill and rod mill luoyang dahua

differences between ball mill and rod mill luoyang dahua

The widely used grinding equipment in concentrators is ball milland rod mill. The two have similarities in appearance and grinding principles, but there are also differences in structure, performance, and use. This article analyzes their similarities and differences from 7 aspects, and tells everyone how to choose a ball mill and a rod mill!

From the analysis of the crushing mechanism, whether ball mill or rod mill, when the cylinder rotates, the grinding medium (ball or rod) installed in the cylinder is lifted to a certain height as the cylinder rotates under the action of friction and centrifugal force. Then it is thrown down at a certain linear speed, so it impacts, grinds and squeezes the material in the jane to make it crush.

The shape ratio of the two barrels is different. The ratio of the length to the diameter of the barrel of the rod mill is generally 1.5-2.0, and the inner surface of the liner on the end cover is a vertical plane. The ratio of the cylinder length to the diameter of the ball mill is small, and in most cases the ratio is only slightly greater than 1.

Rod mills usually use steel rods with a diameter of 50-100mm as grinding media, while ball mills use steel balls as grinding media. The difference in grinding bodies is the main difference between the two.

3. Type analysis (different discharging methods) in ball mills, grid-type ball mills and overflow-type ball mills are commonly used (named from different discharging section structures), while rod mills do not use grid plates to discharge ore, only overflow. There are two types of type and open type. The diameter of the hollow shaft at the discharge end is generally larger than that of the ball mill of the same specification.

The medium filling rate refers to the percentage of the grinding medium in the volume of the mill. For different grinding methods, mill structures, operating conditions and media shapes, the media filling rate has a suitable range, and too high or too low will affect the grinding effect. Generally, the filling rate of ball mill is 40%-50%, and that of rod mill is 35%-45%. In addition, the filling rate of self-mill is 25%-40%, and that of gravel mill is about 43%.

During operation, the ball mill has no inertial impact, which ensures the normal and efficient operation of the equipment, reduces the downtime of the equipment, and improves the efficiency of production.

When heavy separation or magnetic separation of tungsten tin ore and other rare metal ores, rod mills are often used to prevent excessive crushing; in the second-stage grinding process, rod mills are generally used as the first-stage grinding equipment to produce. The ability is greater, and the efficiency is also higher. When processing soft or not too hard ores, rod mills can be used instead of short-head cone crushers for fine crushing, which is not only simple in configuration, but also low in cost, and simplifies dust removal in the workshop.

The characteristic of the rod mill process is that the product is relatively coarse, but the particle size is uniform, contains less coarse particles and sludge, and is lighter in over-crushing. The particle size characteristics of the rod mill product are related to the ore crushed by the rod.

The performance characteristics of the ball mill are high production capacity, strong adaptability to materials, high fineness of the materials, fine discharging particle size, easy fine grinding, and significant energy saving, but the phenomenon of over-crushing is serious.

Luoyang Dahua Heavy Machinery Co., Ltd. is located in luoyang, the ancient capital of A millennium, mainly engaged in all kinds of crushing, screening, grinding, washing, feeding, conveying, environmental protection, dust removal and other equipment research and development and production manufacturing.

difference between sag mill vs ball mill - mech4study

difference between sag mill vs ball mill - mech4study

In ancient time, the mills were operated with muscle power (by hands), water animals and wind. They were totally based on the mechanical energy by natural resources and living beings.There are many types of mills which are used in the grinding industries. Today we will discuss about two important mill, sag mill and ball mill.Sag Mill vs Ball Mill:Semi-Autogenous Grinding Mill SAG Mill:SAG is the abbreviated form for Semi-Autogenous Grinding Mill. This type of Mill is used for grinding large fragments into small pieces. Pieces are then used for further processing. The SAG mills are generally used in pre-processing of any type of material in grinding process. SAG mills are also known as first stage grinders. These heavy output SAG mills are usually powered by electricity. As requirements and needs in grinding field are enhanced. Improved SAG mills came in trend, which gives highly rated production. These mills are one of the most used and necessary equipment in grinding.Image SourceWorking:SAG mill make use of steel balls included with some large and hard rocks for grinding. These mills utilize the balls in making the large fragments of materials broken into pieces. The ball charge of a SAG mill is about 9% to 20%.This process takes place inside the large rotating drum of SAG mill which is filled with balls partially. Interior of the drum uses the lifting plates. These plates inside the drum are responsible for picking the grinding material up to fall down again throughout the rotations. Repeated collisions between the steel balls and raw materials (ore), divides the material into finer and smaller pieces. This whole process takes place inside the large drum of SAG mill.Application:SAG mills are very important equipment of industrial mining. SAG mills are commonly used in mining fields. From mined coal, it separates out some precious metals. In the mining, some precious metals found are like gold, silver, nickel, and copper etc.Ball Mills:Ball mill is a fine grinder. A horizontal or vertical rotating cylinder which is filled partially with the balls of ceramics, small rocks and balls made from stainless steel. The ball charge of a SAG mill is about 29% to 30%. By friction and influence of tumbling balls inside rotating cylinder grinds the raw material to the required fineness. The internal machinery of ball mill grinds the raw material into the powder-like material, And if extreme fineness and refinery are required then rotation go on continue.Image SourceApplicationIn the production of Portland cement ball, mills are used. Ball mills are used where the fine grinding of raw material is required. Lite versions (small versions) of ball mills are used in laboratories for quality assurance of sample grinding material. These mills also play a significant role in the mechanism of cold welding and in the production of alloys. It is also used to create pulverized coal in thermal power plant.S.No.SAG MILLBALL MILL1.SAG mill is the primary tool for grinding. SAG mill is used before the other mills.Ball mill is a secondary, and it is used after the SAG mill.2.SAG mill breaks the raw material into pieces for the further grinding.Ball mill is used to grind the pieces of raw material intopowder-like structures.3.It does not create pulverized form of matter.It creates pulverized form of matter.4.SAG mill used for separating out the precious metals from mined coalBall mill is used to the production of Portland cement.5.It uses about 10 20 % of metal balls into the cylinder.It uses about 30-40% metal ball.This is all about difference between sag mill vs ball mill. If you have any query regarding this article, ask by commenting. If you like this article, dont forget to share it on social networks. Subscribe our website for more informative articles. Thanks for reading it.

Sag Mill vs Ball Mill:Semi-Autogenous Grinding Mill SAG Mill:SAG is the abbreviated form for Semi-Autogenous Grinding Mill. This type of Mill is used for grinding large fragments into small pieces. Pieces are then used for further processing. The SAG mills are generally used in pre-processing of any type of material in grinding process. SAG mills are also known as first stage grinders. These heavy output SAG mills are usually powered by electricity. As requirements and needs in grinding field are enhanced. Improved SAG mills came in trend, which gives highly rated production. These mills are one of the most used and necessary equipment in grinding.Image SourceWorking:SAG mill make use of steel balls included with some large and hard rocks for grinding. These mills utilize the balls in making the large fragments of materials broken into pieces. The ball charge of a SAG mill is about 9% to 20%.This process takes place inside the large rotating drum of SAG mill which is filled with balls partially. Interior of the drum uses the lifting plates. These plates inside the drum are responsible for picking the grinding material up to fall down again throughout the rotations. Repeated collisions between the steel balls and raw materials (ore), divides the material into finer and smaller pieces. This whole process takes place inside the large drum of SAG mill.Application:SAG mills are very important equipment of industrial mining. SAG mills are commonly used in mining fields. From mined coal, it separates out some precious metals. In the mining, some precious metals found are like gold, silver, nickel, and copper etc.Ball Mills:Ball mill is a fine grinder. A horizontal or vertical rotating cylinder which is filled partially with the balls of ceramics, small rocks and balls made from stainless steel. The ball charge of a SAG mill is about 29% to 30%. By friction and influence of tumbling balls inside rotating cylinder grinds the raw material to the required fineness. The internal machinery of ball mill grinds the raw material into the powder-like material, And if extreme fineness and refinery are required then rotation go on continue.Image SourceApplicationIn the production of Portland cement ball, mills are used. Ball mills are used where the fine grinding of raw material is required. Lite versions (small versions) of ball mills are used in laboratories for quality assurance of sample grinding material. These mills also play a significant role in the mechanism of cold welding and in the production of alloys. It is also used to create pulverized coal in thermal power plant.S.No.SAG MILLBALL MILL1.SAG mill is the primary tool for grinding. SAG mill is used before the other mills.Ball mill is a secondary, and it is used after the SAG mill.2.SAG mill breaks the raw material into pieces for the further grinding.Ball mill is used to grind the pieces of raw material intopowder-like structures.3.It does not create pulverized form of matter.It creates pulverized form of matter.4.SAG mill used for separating out the precious metals from mined coalBall mill is used to the production of Portland cement.5.It uses about 10 20 % of metal balls into the cylinder.It uses about 30-40% metal ball.This is all about difference between sag mill vs ball mill. If you have any query regarding this article, ask by commenting. If you like this article, dont forget to share it on social networks. Subscribe our website for more informative articles. Thanks for reading it.

Image SourceWorking:SAG mill make use of steel balls included with some large and hard rocks for grinding. These mills utilize the balls in making the large fragments of materials broken into pieces. The ball charge of a SAG mill is about 9% to 20%.This process takes place inside the large rotating drum of SAG mill which is filled with balls partially. Interior of the drum uses the lifting plates. These plates inside the drum are responsible for picking the grinding material up to fall down again throughout the rotations. Repeated collisions between the steel balls and raw materials (ore), divides the material into finer and smaller pieces. This whole process takes place inside the large drum of SAG mill.Application:SAG mills are very important equipment of industrial mining. SAG mills are commonly used in mining fields. From mined coal, it separates out some precious metals. In the mining, some precious metals found are like gold, silver, nickel, and copper etc.Ball Mills:Ball mill is a fine grinder. A horizontal or vertical rotating cylinder which is filled partially with the balls of ceramics, small rocks and balls made from stainless steel. The ball charge of a SAG mill is about 29% to 30%. By friction and influence of tumbling balls inside rotating cylinder grinds the raw material to the required fineness. The internal machinery of ball mill grinds the raw material into the powder-like material, And if extreme fineness and refinery are required then rotation go on continue.Image SourceApplicationIn the production of Portland cement ball, mills are used. Ball mills are used where the fine grinding of raw material is required. Lite versions (small versions) of ball mills are used in laboratories for quality assurance of sample grinding material. These mills also play a significant role in the mechanism of cold welding and in the production of alloys. It is also used to create pulverized coal in thermal power plant.S.No.SAG MILLBALL MILL1.SAG mill is the primary tool for grinding. SAG mill is used before the other mills.Ball mill is a secondary, and it is used after the SAG mill.2.SAG mill breaks the raw material into pieces for the further grinding.Ball mill is used to grind the pieces of raw material intopowder-like structures.3.It does not create pulverized form of matter.It creates pulverized form of matter.4.SAG mill used for separating out the precious metals from mined coalBall mill is used to the production of Portland cement.5.It uses about 10 20 % of metal balls into the cylinder.It uses about 30-40% metal ball.This is all about difference between sag mill vs ball mill. If you have any query regarding this article, ask by commenting. If you like this article, dont forget to share it on social networks. Subscribe our website for more informative articles. Thanks for reading it.

SAG mill make use of steel balls included with some large and hard rocks for grinding. These mills utilize the balls in making the large fragments of materials broken into pieces. The ball charge of a SAG mill is about 9% to 20%.This process takes place inside the large rotating drum of SAG mill which is filled with balls partially. Interior of the drum uses the lifting plates. These plates inside the drum are responsible for picking the grinding material up to fall down again throughout the rotations. Repeated collisions between the steel balls and raw materials (ore), divides the material into finer and smaller pieces. This whole process takes place inside the large drum of SAG mill.Application:SAG mills are very important equipment of industrial mining. SAG mills are commonly used in mining fields. From mined coal, it separates out some precious metals. In the mining, some precious metals found are like gold, silver, nickel, and copper etc.Ball Mills:Ball mill is a fine grinder. A horizontal or vertical rotating cylinder which is filled partially with the balls of ceramics, small rocks and balls made from stainless steel. The ball charge of a SAG mill is about 29% to 30%. By friction and influence of tumbling balls inside rotating cylinder grinds the raw material to the required fineness. The internal machinery of ball mill grinds the raw material into the powder-like material, And if extreme fineness and refinery are required then rotation go on continue.Image SourceApplicationIn the production of Portland cement ball, mills are used. Ball mills are used where the fine grinding of raw material is required. Lite versions (small versions) of ball mills are used in laboratories for quality assurance of sample grinding material. These mills also play a significant role in the mechanism of cold welding and in the production of alloys. It is also used to create pulverized coal in thermal power plant.S.No.SAG MILLBALL MILL1.SAG mill is the primary tool for grinding. SAG mill is used before the other mills.Ball mill is a secondary, and it is used after the SAG mill.2.SAG mill breaks the raw material into pieces for the further grinding.Ball mill is used to grind the pieces of raw material intopowder-like structures.3.It does not create pulverized form of matter.It creates pulverized form of matter.4.SAG mill used for separating out the precious metals from mined coalBall mill is used to the production of Portland cement.5.It uses about 10 20 % of metal balls into the cylinder.It uses about 30-40% metal ball.This is all about difference between sag mill vs ball mill. If you have any query regarding this article, ask by commenting. If you like this article, dont forget to share it on social networks. Subscribe our website for more informative articles. Thanks for reading it.

Application:SAG mills are very important equipment of industrial mining. SAG mills are commonly used in mining fields. From mined coal, it separates out some precious metals. In the mining, some precious metals found are like gold, silver, nickel, and copper etc.Ball Mills:Ball mill is a fine grinder. A horizontal or vertical rotating cylinder which is filled partially with the balls of ceramics, small rocks and balls made from stainless steel. The ball charge of a SAG mill is about 29% to 30%. By friction and influence of tumbling balls inside rotating cylinder grinds the raw material to the required fineness. The internal machinery of ball mill grinds the raw material into the powder-like material, And if extreme fineness and refinery are required then rotation go on continue.Image SourceApplicationIn the production of Portland cement ball, mills are used. Ball mills are used where the fine grinding of raw material is required. Lite versions (small versions) of ball mills are used in laboratories for quality assurance of sample grinding material. These mills also play a significant role in the mechanism of cold welding and in the production of alloys. It is also used to create pulverized coal in thermal power plant.S.No.SAG MILLBALL MILL1.SAG mill is the primary tool for grinding. SAG mill is used before the other mills.Ball mill is a secondary, and it is used after the SAG mill.2.SAG mill breaks the raw material into pieces for the further grinding.Ball mill is used to grind the pieces of raw material intopowder-like structures.3.It does not create pulverized form of matter.It creates pulverized form of matter.4.SAG mill used for separating out the precious metals from mined coalBall mill is used to the production of Portland cement.5.It uses about 10 20 % of metal balls into the cylinder.It uses about 30-40% metal ball.This is all about difference between sag mill vs ball mill. If you have any query regarding this article, ask by commenting. If you like this article, dont forget to share it on social networks. Subscribe our website for more informative articles. Thanks for reading it.

SAG mills are very important equipment of industrial mining. SAG mills are commonly used in mining fields. From mined coal, it separates out some precious metals. In the mining, some precious metals found are like gold, silver, nickel, and copper etc.Ball Mills:Ball mill is a fine grinder. A horizontal or vertical rotating cylinder which is filled partially with the balls of ceramics, small rocks and balls made from stainless steel. The ball charge of a SAG mill is about 29% to 30%. By friction and influence of tumbling balls inside rotating cylinder grinds the raw material to the required fineness. The internal machinery of ball mill grinds the raw material into the powder-like material, And if extreme fineness and refinery are required then rotation go on continue.Image SourceApplicationIn the production of Portland cement ball, mills are used. Ball mills are used where the fine grinding of raw material is required. Lite versions (small versions) of ball mills are used in laboratories for quality assurance of sample grinding material. These mills also play a significant role in the mechanism of cold welding and in the production of alloys. It is also used to create pulverized coal in thermal power plant.S.No.SAG MILLBALL MILL1.SAG mill is the primary tool for grinding. SAG mill is used before the other mills.Ball mill is a secondary, and it is used after the SAG mill.2.SAG mill breaks the raw material into pieces for the further grinding.Ball mill is used to grind the pieces of raw material intopowder-like structures.3.It does not create pulverized form of matter.It creates pulverized form of matter.4.SAG mill used for separating out the precious metals from mined coalBall mill is used to the production of Portland cement.5.It uses about 10 20 % of metal balls into the cylinder.It uses about 30-40% metal ball.This is all about difference between sag mill vs ball mill. If you have any query regarding this article, ask by commenting. If you like this article, dont forget to share it on social networks. Subscribe our website for more informative articles. Thanks for reading it.

Ball Mills:Ball mill is a fine grinder. A horizontal or vertical rotating cylinder which is filled partially with the balls of ceramics, small rocks and balls made from stainless steel. The ball charge of a SAG mill is about 29% to 30%. By friction and influence of tumbling balls inside rotating cylinder grinds the raw material to the required fineness. The internal machinery of ball mill grinds the raw material into the powder-like material, And if extreme fineness and refinery are required then rotation go on continue.Image SourceApplicationIn the production of Portland cement ball, mills are used. Ball mills are used where the fine grinding of raw material is required. Lite versions (small versions) of ball mills are used in laboratories for quality assurance of sample grinding material. These mills also play a significant role in the mechanism of cold welding and in the production of alloys. It is also used to create pulverized coal in thermal power plant.S.No.SAG MILLBALL MILL1.SAG mill is the primary tool for grinding. SAG mill is used before the other mills.Ball mill is a secondary, and it is used after the SAG mill.2.SAG mill breaks the raw material into pieces for the further grinding.Ball mill is used to grind the pieces of raw material intopowder-like structures.3.It does not create pulverized form of matter.It creates pulverized form of matter.4.SAG mill used for separating out the precious metals from mined coalBall mill is used to the production of Portland cement.5.It uses about 10 20 % of metal balls into the cylinder.It uses about 30-40% metal ball.This is all about difference between sag mill vs ball mill. If you have any query regarding this article, ask by commenting. If you like this article, dont forget to share it on social networks. Subscribe our website for more informative articles. Thanks for reading it.

Image SourceApplicationIn the production of Portland cement ball, mills are used. Ball mills are used where the fine grinding of raw material is required. Lite versions (small versions) of ball mills are used in laboratories for quality assurance of sample grinding material. These mills also play a significant role in the mechanism of cold welding and in the production of alloys. It is also used to create pulverized coal in thermal power plant.S.No.SAG MILLBALL MILL1.SAG mill is the primary tool for grinding. SAG mill is used before the other mills.Ball mill is a secondary, and it is used after the SAG mill.2.SAG mill breaks the raw material into pieces for the further grinding.Ball mill is used to grind the pieces of raw material intopowder-like structures.3.It does not create pulverized form of matter.It creates pulverized form of matter.4.SAG mill used for separating out the precious metals from mined coalBall mill is used to the production of Portland cement.5.It uses about 10 20 % of metal balls into the cylinder.It uses about 30-40% metal ball.This is all about difference between sag mill vs ball mill. If you have any query regarding this article, ask by commenting. If you like this article, dont forget to share it on social networks. Subscribe our website for more informative articles. Thanks for reading it.

In the production of Portland cement ball, mills are used. Ball mills are used where the fine grinding of raw material is required. Lite versions (small versions) of ball mills are used in laboratories for quality assurance of sample grinding material. These mills also play a significant role in the mechanism of cold welding and in the production of alloys. It is also used to create pulverized coal in thermal power plant.S.No.SAG MILLBALL MILL1.SAG mill is the primary tool for grinding. SAG mill is used before the other mills.Ball mill is a secondary, and it is used after the SAG mill.2.SAG mill breaks the raw material into pieces for the further grinding.Ball mill is used to grind the pieces of raw material intopowder-like structures.3.It does not create pulverized form of matter.It creates pulverized form of matter.4.SAG mill used for separating out the precious metals from mined coalBall mill is used to the production of Portland cement.5.It uses about 10 20 % of metal balls into the cylinder.It uses about 30-40% metal ball.This is all about difference between sag mill vs ball mill. If you have any query regarding this article, ask by commenting. If you like this article, dont forget to share it on social networks. Subscribe our website for more informative articles. Thanks for reading it.

S.No.SAG MILLBALL MILL1.SAG mill is the primary tool for grinding. SAG mill is used before the other mills.Ball mill is a secondary, and it is used after the SAG mill.2.SAG mill breaks the raw material into pieces for the further grinding.Ball mill is used to grind the pieces of raw material intopowder-like structures.3.It does not create pulverized form of matter.It creates pulverized form of matter.4.SAG mill used for separating out the precious metals from mined coalBall mill is used to the production of Portland cement.5.It uses about 10 20 % of metal balls into the cylinder.It uses about 30-40% metal ball.This is all about difference between sag mill vs ball mill. If you have any query regarding this article, ask by commenting. If you like this article, dont forget to share it on social networks. Subscribe our website for more informative articles. Thanks for reading it.

ball mill - an overview | sciencedirect topics

ball mill - an overview | sciencedirect topics

The ball mill accepts the SAG or AG mill product. Ball mills give a controlled final grind and produce flotation feed of a uniform size. Ball mills tumble iron or steel balls with the ore. The balls are initially 510 cm diameter but gradually wear away as grinding of the ore proceeds. The feed to ball mills (dry basis) is typically 75 vol.-% ore and 25% steel.

The ball mill is operated in closed circuit with a particle-size measurement device and size-control cyclones. The cyclones send correct-size material on to flotation and direct oversize material back to the ball mill for further grinding.

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.

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).

Planetary ball mills. A planetary ball mill consists of at least one grinding jar, which is arranged eccentrically on a so-called sun wheel. The direction of movement of the sun wheel is opposite to that of the grinding jars according to a fixed ratio. The grinding balls in the grinding jars are subjected to superimposed rotational movements. The jars are moved around their own axis and, in the opposite direction, around the axis of the sun wheel at uniform speed and uniform rotation ratios. The result is that the superimposition of the centrifugal forces changes constantly (Coriolis motion). The grinding balls describe a semicircular movement, separate from the inside wall, and collide with the opposite surface at high impact energy. The difference in speeds produces an interaction between frictional and impact forces, which releases high dynamic energies. The interplay between these forces produces the high and very effective degree of size reduction of the planetary ball mill. Planetary ball mills are smaller than common ball mills, and are mainly used in laboratories for grinding sample material down to very small sizes.

Vibration mill. Twin- and three-tube vibrating mills are driven by an unbalanced drive. The entire filling of the grinding cylinders, which comprises the grinding media and the feed material, constantly receives impulses from the circular vibrations in the body of the mill. The grinding action itself is produced by the rotation of the grinding media in the opposite direction to the driving rotation and by continuous head-on collisions of the grinding media. The residence time of the material contained in the grinding cylinders is determined by the quantity of the flowing material. The residence time can also be influenced by using damming devices. The sample passes through the grinding cylinders in a helical curve and slides down from the inflow to the outflow. The high degree of fineness achieved is the result of this long grinding procedure. Continuous feeding is carried out by vibrating feeders, rotary valves, or conveyor screws. The product is subsequently conveyed either pneumatically or mechanically. They are basically used to homogenize food and feed.

CryoGrinder. As small samples (100 mg or <20 ml) are difficult to recover from a standard mortar and pestle, the CryoGrinder serves as an alternative. The CryoGrinder is a miniature mortar shaped as a small well and a tightly fitting pestle. The CryoGrinder is prechilled, then samples are added to the well and ground by a handheld cordless screwdriver. The homogenization and collection of the sample is highly efficient. In environmental analysis, this system is used when very small samples are available, such as small organisms or organs (brains, hepatopancreas, etc.).

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.

A ball mill is a relatively simple apparatus in which the motion of the reactor, or of a part of it, induces a series of collisions of balls with each other and with the reactor walls (Suryanarayana, 2001). At each collision, a fraction of the powder inside the reactor is trapped between the colliding surfaces of the milling tools and submitted to a mechanical load at relatively high strain rates (Suryanarayana, 2001). This load generates a local nonhydrostatic mechanical stress at every point of contact between any pair of powder particles. The specific features of the deformation processes induced by these stresses depend on the intensity of the mechanical stresses themselves, on the details of the powder particle arrangement, that is on the topology of the contact network, and on the physical and chemical properties of powders (Martin et al., 2003; Delogu, 2008a). At the end of any given collision event, the powder that has been trapped is remixed with the powder that has not undergone this process. Correspondingly, at any instant in the mechanical processing, the whole powder charge includes fractions of powder that have undergone a different number of collisions.

The individual reactive processes at the perturbed interface between metallic elements are expected to occur on timescales that are, at most, comparable with the collision duration (Hammerberg et al., 1998; Urakaev and Boldyrev, 2000; Lund and Schuh, 2003; Delogu and Cocco, 2005a,b). Therefore, unless the ball mill is characterized by unusually high rates of powder mixing and frequency of collisions, reactive events initiated by local deformation processes at a given collision are not affected by a successive collision. Indeed, the time interval between successive collisions is significantly longer than the time period required by local structural perturbations for full relaxation (Hammerberg et al., 1998; Urakaev and Boldyrev, 2000; Lund and Schuh, 2003; Delogu and Cocco, 2005a,b).

These few considerations suffice to point out the two fundamental features of powder processing by ball milling, which in turn govern the MA processes in ball mills. First, mechanical processing by ball milling is a discrete processing method. Second, it has statistical character. All of this has important consequences for the study of the kinetics of MA processes. The fact that local deformation events are connected to individual collisions suggests that absolute time is not an appropriate reference quantity to describe mechanically induced phase transformations. Such a description should rather be made as a function of the number of collisions (Delogu et al., 2004). A satisfactory description of the MA kinetics must also account for the intrinsic statistical character of powder processing by ball milling. The amount of powder trapped in any given collision, at the end of collision is indeed substantially remixed with the other powder in the reactor. It follows that the same amount, or a fraction of it, could at least in principle be trapped again in the successive collision.

This is undoubtedly a difficult aspect to take into account in a mathematical description of MA kinetics. There are at least two extreme cases to consider. On the one hand, it could be assumed that the powder trapped in a given collision cannot be trapped in the successive one. On the other, it could be assumed that powder mixing is ideal and that the amount of powder trapped at a given collision has the same probability of being processed in the successive collision. Both these cases allow the development of a mathematical model able to describe the relationship between apparent kinetics and individual collision events. However, the latter assumption seems to be more reliable than the former one, at least for commercial mills characterized by relatively complex displacement in the reactor (Manai et al., 2001, 2004).

A further obvious condition for the successful development of a mathematical description of MA processes is the one related to the uniformity of collision regimes. More specifically, it is highly desirable that the powders trapped at impact always experience the same conditions. This requires the control of the ball dynamics inside the reactor, which can be approximately obtained by using a single milling ball and an amount of powder large enough to assure inelastic impact conditions (Manai et al., 2001, 2004; Delogu et al., 2004). In fact, the use of a single milling ball avoids impacts between balls, which have a remarkable disordering effect on the ball dynamics, whereas inelastic impact conditions permit the establishment of regular and periodic ball dynamics (Manai et al., 2001, 2004; Delogu et al., 2004).

All of the above assumptions and observations represent the basis and guidelines for the development of the mathematical model briefly outlined in the following. It has been successfully applied to the case of a Spex Mixer/ Mill mod. 8000, but the same approach can, in principle, be used for other ball mills.

The Planetary ball mills are the most popular mills used in MM, MA, and MD scientific researches for synthesizing almost all of the materials presented in Figure 1.1. In this type of mill, the milling media have considerably high energy, because milling stock and balls come off the inner wall of the vial (milling bowl or 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, as schematically presented in Figure 2.17.

However, there are some companies in the world who manufacture and sell number of planetary-type ball mills; Fritsch GmbH (www.fritsch-milling.com) and Retsch (http://www.retsch.com) are considered to be the oldest and principal companies in this area.

Fritsch produces different types of planetary ball mills with different capacities and rotation speeds. Perhaps, Fritsch Pulverisette P5 (Figure 2.18(a)) and Fritsch Pulverisette P6 (Figure 2.18(b)) are the most popular models of Fritsch planetary ball mills. A variety of vials and balls made of different materials with different capacities, starting from 80ml up to 500ml, are available for the Fritsch Pulverisette planetary ball mills; these include tempered steel, stainless steel, tungsten carbide, agate, sintered corundum, silicon nitride, and zirconium oxide. Figure 2.19 presents 80ml-tempered steel vial (a) and 500ml-agate vials (b) together with their milling media that are made of the same materials.

Figure 2.18. Photographs of Fritsch planetary-type high-energy ball mill of (a) Pulverisette P5 and (b) Pulverisette P6. The equipment is housed in the Nanotechnology Laboratory, Energy and Building Research Center (EBRC), Kuwait Institute for Scientific Research (KISR).

Figure 2.19. Photographs of the vials used for Fritsch planetary ball mills with capacity of (a) 80ml and (b) 500ml. The vials and the balls shown in (a) and (b) are made of tempered steel agate materials, respectively (Nanotechnology Laboratory, Energy and Building Research Center (EBRC), Kuwait Institute for Scientific Research (KISR)).

More recently and in year 2011, Fritsch GmbH (http://www.fritsch-milling.com) introduced a new high-speed and versatile planetary ball mill called Planetary Micro Mill PULVERISETTE 7 (Figure 2.20). The company claims this new ball mill will be helpful to enable extreme high-energy ball milling at rotational speed reaching to 1,100rpm. This allows the new mill to achieve sensational centrifugal accelerations up to 95 times Earth gravity. They also mentioned that the energy application resulted from this new machine is about 150% greater than the classic planetary mills. Accordingly, it is expected that this new milling machine will enable the researchers to get their milled powders in short ball-milling time with fine powder particle sizes that can reach to be less than 1m in diameter. The vials available for this new type of mill have sizes of 20, 45, and 80ml. Both the vials and balls can be made of the same materials, which are used in the manufacture of large vials used for the classic Fritsch planetary ball mills, as shown in the previous text.

Retsch has also produced a number of capable high-energy planetary ball mills with different capacities (http://www.retsch.com/products/milling/planetary-ball-mills/); namely Planetary Ball Mill PM 100 (Figure 2.21(a)), Planetary Ball Mill PM 100 CM, Planetary Ball Mill PM 200, and Planetary Ball Mill PM 400 (Figure 2.21(b)). Like Fritsch, Retsch offers high-quality ball-milling vials with different capacities (12, 25, 50, 50, 125, 250, and 500ml) and balls of different diameters (540mm), as exemplified in Figure 2.22. These milling tools can be made of hardened steel as well as other different materials such as carbides, nitrides, and oxides.

Figure 2.21. Photographs of Retsch planetary-type high-energy ball mill of (a) PM 100 and (b) PM 400. The equipment is housed in the Nanotechnology Laboratory, Energy and Building Research Center (EBRC), Kuwait Institute for Scientific Research (KISR).

Figure 2.22. Photographs of the vials used for Retsch planetary ball mills with capacity of (a) 80ml, (b) 250ml, and (c) 500ml. The vials and the balls shown are made of tempered steel (Nanotechnology Laboratory, Energy and Building Research Center (EBRC), Kuwait Institute for Scientific Research (KISR)).

Both Fritsch and Retsch companies have offered special types of vials that allow monitoring and measure the gas pressure and temperature inside the vial during the high-energy planetary ball-milling process. Moreover, these vials allow milling the powders under inert (e.g., argon or helium) or reactive gas (e.g., hydrogen or nitrogen) with a maximum gas pressure of 500kPa (5bar). It is worth mentioning here that such a development made on the vials design allows the users and researchers to monitor the progress tackled during the MA and MD processes by following up the phase transformations and heat realizing upon RBM, where the interaction of the gas used with the freshly created surfaces of the powders during milling (adsorption, absorption, desorption, and decomposition) can be monitored. Furthermore, the data of the temperature and pressure driven upon using this system is very helpful when the ball mills are used for the formation of stable (e.g., intermetallic compounds) and metastable (e.g., amorphous and nanocrystalline materials) phases. In addition, measuring the vial temperature during blank (without samples) high-energy ball mill can be used as an indication to realize the effects of friction, impact, and conversion processes.

More recently, Evico-magnetics (www.evico-magnetics.de) has manufactured an extraordinary high-pressure milling vial with gas-temperature-monitoring (GTM) system. Likewise both system produced by Fritsch and Retsch, the developed system produced by Evico-magnetics, allowing RBM but at very high gas pressure that can reach to 15,000kPa (150bar). In addition, it allows in situ monitoring of temperature and of pressure by incorporating GTM. The vials, which can be used with any planetary mills, are made of hardened steel with capacity up to 220ml. The manufacturer offers also two-channel system for simultaneous use of two milling vials.

Using different ball mills as examples, it has been shown that, on the basis of the theory of glancing collision of rigid bodies, the theoretical calculation of tPT conditions and the kinetics of mechanochemical processes are possible for the reactors that are intended to perform different physicochemical processes during mechanical treatment of solids. According to the calculations, the physicochemical effect of mechanochemical reactors is due to short-time impulses of pressure (P = ~ 10101011 dyn cm2) with shift, and temperature T(x, t). The highest temperature impulse T ~ 103 K are caused by the dry friction phenomenon.

Typical spatial and time parameters of the impactfriction interaction of the particles with a size R ~ 104 cm are as follows: localization region, x ~ 106 cm; time, t ~ 108 s. On the basis of the obtained theoretical results, the effect of short-time contact fusion of particles treated in various comminuting devices can play a key role in the mechanism of activation and chemical reactions for wide range of mechanochemical processes. This role involves several aspects, that is, the very fact of contact fusion transforms the solid phase process onto another qualitative level, judging from the mass transfer coefficients. The spatial and time characteristics of the fused zone are such that quenching of non-equilibrium defects and intermediate products of chemical reactions occurs; solidification of the fused zone near the contact point results in the formation of a nanocrystal or nanoamor- phous state. The calculation models considered above and the kinetic equations obtained using them allow quantitative ab initio estimates of rate constants to be performed for any specific processes of mechanical activation and chemical transformation of the substances in ball mills.

There are two classes of ball mills: planetary and mixer (also called swing) mill. The terms high-speed vibration milling (HSVM), high-speed ball milling (HSBM), and planetary ball mill (PBM) are often used. The commercial apparatus are PBMs Fritsch P-5 and Fritsch Pulverisettes 6 and 7 classic line, the Retsch shaker (or mixer) mills ZM1, MM200, MM400, AS200, the Spex 8000, 6750 freezer/mill SPEX CertiPrep, and the SWH-0.4 vibrational ball mill. In some instances temperature controlled apparatus were used (58MI1); freezer/mills were used in some rare cases (13MOP1824).

The balls are made of stainless steel, agate (SiO2), zirconium oxide (ZrO2), or silicon nitride (Si3N). The use of stainless steel will contaminate the samples with steel particles and this is a problem both for solid-state NMR and for drug purity.

However, there are many types of ball mills (see Chapter 2 for more details), such as drum ball mills, jet ball mills, bead-mills, roller ball mills, vibration ball mills, and planetary ball mills, they can be grouped or classified into two types according to their rotation speed, as follows: (i) high-energy ball mills and (ii) low-energy ball mills. Table 3.1 presents characteristics and comparison between three types of ball mills (attritors, vibratory mills, planetary ball mills and roller mills) that are intensively used on MA, MD, and MM techniques.

In fact, choosing the right ball mill depends on the objectives of the process and the sort of materials (hard, brittle, ductile, etc.) that will be subjecting to the ball-milling process. For example, the characteristics and properties of those ball mills used for reduction in the particle size of the starting materials via top-down approach, or so-called mechanical milling (MM process), or for mechanically induced solid-state mixing for fabrications of composite and nanocomposite powders may differ widely from those mills used for achieving mechanically induced solid-state reaction (MISSR) between the starting reactant materials of elemental powders (MA process), or for tackling dramatic phase transformation changes on the structure of the starting materials (MD). Most of the ball mills in the market can be employed for different purposes and for preparing of wide range of new materials.

Martinez-Sanchez et al. [4] have pointed out that employing of high-energy ball mills not only contaminates the milled amorphous powders with significant volume fractions of impurities that come from milling media that move at high velocity, but it also affects the stability and crystallization properties of the formed amorphous phase. They have proved that the properties of the formed amorphous phase (Mo53Ni47) powder depends on the type of the ball-mill equipment (SPEX 8000D Mixer/Mill and Zoz Simoloter mill) used in their important investigations. This was indicated by the high contamination content of oxygen on the amorphous powders prepared by SPEX 8000D Mixer/Mill, when compared with the corresponding amorphous powders prepared by Zoz Simoloter mill. Accordingly, they have attributed the poor stabilities, indexed by the crystallization temperature of the amorphous phase formed by SPEX 8000D Mixer/Mill to the presence of foreign matter (impurities).

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