polish grinding of gears for higher transmission efficiency | gear solutions magazine your resource to the gear industry

polish grinding of gears for higher transmission efficiency | gear solutions magazine your resource to the gear industry

A new gear polish grinding process is presented to show that improved surface finishes increase the overall efficiency of transmissions, and the resulting higher bearing ratios reduce micropitting. A cost-efficient manufacturing method adapted for large-scale manufacture is also introduced.

The established continuous generating method was used as the base technology for the polish grinding process, which is distinct from the vibratory superfinishing used in many non-automotive applications. Continuous generating grinding is an established process for the hard finishing of gears. Based on a dressable grinding worm, this process has proven itself, both in terms of flexibility and high productivity.

In principle, the kinematics of this process can be understood as a worm drive (see Figure 1 and Figure 2) with additional abrasive machining movements, consisting of an infeed X, a vertical feed-rate Z, and a lateral shifting motion Y. Without interrupting the gear grinding cycle, polish grinding is performed as a final machining sequence on the manufacturers existing continuous generating gear grinding machines while the workpiece remains clamped on the part holder during both grinding and polish grinding. Polish grinding, as a general rule, consists of one polish grinding pass with the resin-bonded section integrated into the end section of the vitrified-bonded threaded grinding wheel, which performs the grinding operation.

During polish grinding, only the roughness peaks are removed, reducing the roughness profile height, therefore, this method increases the contact bearing area of the gear flanks while the geometrical accuracy of the gear flanks is not affected. The polish grinding process delivers surface qualities with mean roughness values of Ra 0.15 m, compared with the standard values of Ra 0.4 m used in the industry on continuous generating-grinding machines.

Polish grinding is performed as a final machining sequence, immediately after conventional grinding, consisting of a roughing and a finishing grinding pass. For this purpose, the threaded wheel is divided into two zones, the grinding and the polishing zone, as shown in Figure 3.

This final sequence consists of polish grinding passes with an elastic resin-bonded section of the threaded grinding wheel. There are some fundamental differences between grinding and polishing. Simply put, grinding uses comparatively larger grit sizes and rigid bond structures. Figure 4 shows the comparison between the 80-grit for grinding and the 800-grit for polish grinding.

Polish grinding uses much finer grit sizes and preferably elastic bonds (see Figure 5). The aim of grinding is to give perfect geometry, a good surface finish, and fast material-removal rates. Polish grinding, as a subsequent step to grinding, should not alter the given part geometry and should result in, visually speaking, a mirror surface finish. However, for engineering purposes, polish grinding should only remove the surface roughness peaks and must leave intact the valley surface roughness so that oil films can adhere to the polish-ground surface. With the roughness profile height removed, the contact area of the gear flanks is increased. As a consequence, the augmented surface contact area allows transmission designers to increase the power density of transmissions.

After the two grinding passes of roughing and finishing, the gear part retracts from the vitrified zone and jumps to the polish grinding zone for its final machining pass, as illustrated in Figure 6.

Using a combined grinding and polish grinding wheel offers a great advantage over the vibratory superfinishing. This is because the vibratory superfinishing process needs a prior grinding process, thus involving two different machine tools and more complex material handling. In gear grinding, all workpieces enter and come off the machine properly oriented and stackable, whereas in vibratory superfinishing, the workpieces are in random orientation and need to be oriented after the process.

The continuous generating process, on the other hand, needs only one machine tool and grinds and polish grinds the component in one clamping operation, which makes it economically feasible for high-volume production. In the combined process, the polish grinding perfectly follows the precision-ground micro and macro geometries of the gear profile and lead. Both polish grinding and vibratory superfinishing remove only the peaks on a ground surface texture, which amounts to approximately 1 micrometer. The grinding pass would typically remove about 0.1 mm per flank prior to polish grinding.

A research project at NASAs Research Center in Glenn (see Figure 7) confirmed in 2002 that superfinished (polished) gears have a fourfold service life in comparison to conventionally ground gears [1]. In this instance, superfinishing was achieved by submersing the gear parts in an abrasive medium and being subjected to a vibration finishing process.

In 2005, the research institute FZG at the Technical University of Munich investigated the load bearing capacity of gear flanks with superfinished gears. In this case, both gears of each tested gear pair were superfinished (polished) to a mean roughness surface of Ra 0.15 m by a vibratory superfinishing process. Based on the first encouraging results, test gear sets were superfinished to Ra 0.140.06 m with different vibratory superfinishing processes and additional shot peening. Results confirmed that superfinishing, combined with shot peening, markedly improved the load-bearing capacity of gear flanks [2].

Subsequent investigations confirmed the aforementioned findings on load-bearing capacity. While these initial investigations were all based on vibratory investigations, Reishauer pursued a different way of superfinishing or polishing, building on the continuous generating-grinding process, which was already well-established for the hard finishing of gears in the automotive industry. The aim was to obtain similar surface finishes as the vibratory method. At the same time, the finishing process had to achieve cycle times that would justify its economy for the automotive industry. Furthermore, the process had to maintain macro and micro geometries of ground gears and not allow any thermal damage to the gears surface structure.

The continuous generating process uses a single vitrified, abrasive threaded wheel. For the purpose of superfinishing or polishing, the vitrified portion of the threaded wheel has been extended by an ultrafine elastic resin-bonded polishing section. This setup allows a gear part to be ground and polished in one clamping operation and with economical cycle times.

The viability of this combined grinding and polish grinding process was independently verified by the FZG Institute at the University of Munich, which pioneered alternative superfinishing methods as described earlier. The gears to be tested were manufactured using three different continuous generating processes:

Subsequent to the grinding operation, the polishing grinding wheel achieved a surface roughness of Rz < 1.0 m and a mean surface roughness of Ra < 0.1 m, which was a reduction of about fourfold in comparison to conventional grinding with vitrified-bonded abrasive grinding wheels.

The polish-ground gear sets were subjected to a load of 1350 N/mm2 (see Figure 9). In comparison to the conventionally ground gears, the polished gears showed a reduction in friction of about 15 percent and resulted in a 4C lower steady state excess temperature, as shown in Figure 10 [2]. The reduction in friction under load should clearly translate into better fuel economy and thereby proportionally lower output of CO2.

The aim of polish grinding is a reduction in surface roughness without altering the gears macro geometry, the gears flank topography, and the material surface structure. The polish grinding process has to remove the peak surface roughness and reduce the core roughness, and it has to leave intact some of the peak valley roughness so that transmission oil films continue to adhere to the transmission gears. Figure 11 and Figure 12 show the difference between the surface roughness of a ground gear and that of a polish-ground gear [3].

Polish grinding, as understood in the context of this paper, is the removal of the surface peaks while leaving on some valley roughness. The surface finish parameter Ra is insufficient to describe this type of surface finish for load-bearing properties. According to Mike Stewart in an SME paper published in 1990, Tribologists have demonstrated that the ideal bearing surface is a smooth one with relatively deep scratches to hold and distribute lubricant, but quantifying and specifying these surfaces has always been a problem. Since its introduction, the bearing area curve has been recognized as the only effective way to characterize these surfaces but is rarely used in specifications [4].

The bearing area curve, also known as the Abbott material ratio curve, is shown in Figure 13. This curve is in fact a much better indicator for the prediction of the bearing capacity wear behavior of gear flanks than the roughness values Ra (see Figure 14). The arithmetic mean deviation Ra does not differentiate between peaks and valleys, therefore, it has a relatively weak information character [5].

Figure 15 shows a conventionally ground gear on the left and a polish-ground gear on the right. These gears have both been produced by the generating-grinding method, with the gear on the right having been polished by the resin-bonded section of a two-zone threaded grinding wheel. The surface roughness of the polish-ground gear has been substantially reduced, therefore, it would cause less friction in the transmission and, consequently, would offer increased load-carrying capacity and a reduction in power loss.

Figure 16 compares the profile and lead macro geometry of a standard-ground gear with that of a polish-ground gear. (Gear data: 20 teeth, module 3, pressure angle 20, helix angle 20, base circle 59.54 mm.)

While the surface finish could be reduced to a surface roughness of Rz < 1.0 m and a mean roughness of Ra < 0.1 m, the macro geometry in the active area of the profile and lead was not affected. However, the polish-ground gear shows some rounding off at the edges of the face width, outside the active area of the gear flank. For automotive gears, this rounding off at the edges can be viewed in a positive light and would not affect the gear performance in any way.

Scientific studies have shown that improved surface finishes increase the overall performance of transmissions as the resulting higher bearing ratios reduce micropitting, thus increasing longevity and efficiency of transmissions. Subsequent customer trials using the Reishauer continuous generating methods have confirmed the research results. Micropitting is known to lead to early gear failure, to overall reduction in transmission efficiency, and to noise problems (NHV). In this example, standard-ground, fine-ground, and polish-ground automatic transmission planetary gears were subjected to a simulation test of 100,000 km on a test rig under changing load and velocity profiles, such that the 100,000 km could be condensed into one week (see Figure 17). Subsequently, the initial gear weight was compared to weight after the simulation. Apart from a marked visual difference, the polish-ground gears showed less micropitting, as borne out by the marked lower loss in weight (see Figure 18).

Further industrial trials have borne out that polish-ground gears have a longer service life, as their gear flank surfaces do not succumb to wear, fatigue, and pitting as fast as standard-ground gears. Figure 19 shows a standard-ground gear shaft on the left and its ground mating gear on the right. This gear pair has been subjected to a test run at a constant load of 800 Nm at 4,500 rpm for a specified time period the standard test procedure of an automotive transmission manufacturer. These ground gears show more scuffing, pitting, and micropitting on their gear flanks.

The same set of gears has been ground- and polish-ground and subjected to the identical test procedure (see Figure 20). While there is some metal fatigue visible in the foot circle of the gear shaft and the mating gear shows minimal wear patterns from pitch circle to tip, the overall post-trial surface quality of the polish-ground gears is far superior.

The results shown here have been witnessed in other trials and are seen as support for the authors claims that polish-ground gears increase transmission efficiency. Highly accurate gear geometries combined with high bearing ratios ensure that transmission designers can increase power density in their products and thereby make a contribution to better fuel economy and lower CO2 output.

The direct integration of polish grinding as a subsequent step in the conventional continuous generating grinding process translates into minimal investment costs if customers already have Reishauer continuous generating gear grinders. Furthermore, the diamond dressing tools remain the same as for the existing conventional processes. Also, polish grinding requires minimal additional operator training. While there is a small increase in cycle time due to the additional polishing stroke, this is outweighed by the gain in product quality. In comparison, the process of vibratory superfinishing requires two machines: a gear grinding machine and a vibratory machine as a subsequent process with additional costs arriving from more complex material handling as the workpieces cannot be oriented in this process.

The added costs entail a CNC software update and the purchase of specific grinding wheels with two distinct abrasive sections: one for grinding and one for polish grinding. The higher process costs over conventional gear grinding and the equipment investment costs are greatly outweighed by the benefits of the reduction in torque loss, the increase in bearing capacity of polish-ground gears, and higher power density in transmissions.

7 common car engine noises & what they mean - mechanic base

7 common car engine noises & what they mean - mechanic base

Does it ever feel like you need to be a sound expert to figure out whats wrong with your car? With all the moving parts, there is a lot that can go wrong. From squealing to grinding, its important you know how to discern the different sounds your car engine is making.

One part you dont ever want any strange noises coming from is the engine. Yet, it happens. Quick diagnosis of the problem can help you save your engine. We review 7 common car engine noises and show you what each means.

Is there ever a time that squealing is good, even outside of the automotive realm? If you hear a squeal coming from under the hood, it should cause alarm. Most times, this annoying sound is related to a loose or worn-out serpentine belt.

However, there are other reasons that your car might be squealing. If its not coming from the engine area, but rather when you turn, your issue might be in the steering system instead. Or, if you hear squealing when you brake, you might need new brake pads.

Theres a distinctive sound that the car engine makes when the oil is low. It resembles a clicking, ticking or tapping noise. Thankfully, this condition is one of the easiest to diagnose; just take a look at the dipstick.

There are many different car systems that can make a grinding noise, but when just focused on the engine alone, it could be due to worn-out bearings. If this is the case, you will hear the grinding sound when driving or idling.

This occurs when the fuel and air mixture in one of the cylinders is detonating at numerous locations simultaneously. Its possible that you put the wrong octane fuel into the system, which can cause this problem.

Weve all heard it once in our lives that distinctive explosion sound that reminds you of fireworks. This condition is known as a backfire. It occurs when the fuel wasnt burned in the combustion chamber and escapes.

Once it moves beyond the combustion chamber, it combusts in the exhaust instead. Any time the fuel/air ratio becomes too rich or lean, a backfire can occur. Allowing your car to backfire only puts it at further risk of damage.

You might see the leak on the exhaust manifold, or it could be harder to find. It could also just be a vacuum line. Either way, the problem should be addressed immediately, especially if the engine is starting to overheat.

Some of the most common reasons for engine popping include a clogged fuel filter, ignition issues, fouled out or dirty spark plugs, damaged plug wires or a faulty catalytic converter. Some of these fixes are simple and low-cost, while others, such as the catalytic converter, are going to be more expensive.

Whatever noise you are hearing, its vital to have it diagnosed immediately. Otherwise, the problem could lead to irreversible engine damage. Luckily it is often enough with smaller repairs when you experience any engine noise.

However, buying a new engine is quite expensive. For most people, its better to purchase a remanufactured engine. If you have a newer car, you will want the warranty that comes with a brand-new motor instead.

A used engine and labor will still likely run $1,500 or more. New gas engines and installation are going to be $3,000 or more. A new Ford V10 engine costs $5,000 or more. However, there are some cars that dont cost as much. For example, a new Ford Focus engine might only be $500 for the engine, not including the labor. If you have a diesel engine, you are looking at a much higher bill.

Founder, owner & main author of Mechanic Base. I have been repairing cars for more than 10 years, specialized in advanced diagnostics & troubleshooting. I have also been a drifting driver and mechanic for over 7 years.

how to troubleshoot a car with clutch noise | yourmechanic advice

how to troubleshoot a car with clutch noise | yourmechanic advice

People make the decision to purchase a manually-shifted vehicle for a wide variety of reasons. For some, it's the fun or flexibility of driving a car with a clutch. However, clutch operated manually-shifted transmissions also come with some hurdles to overcome, one of which is premature wear and tear of different clutch components. In many cases, when the clutch begins to wear out, some of the moving parts will make weird sounds that are noticeable while the vehicle is idling or is in motion.

If you've noticed some sounds coming from the center portion of your vehicle, it may be contributed to a clutch that has broken or some of the individual components are wearing out. Either way, trying to troubleshoot a noisy clutch can be complex and time consuming. Noted below are a few of the common reasons why you might hear noises coming from the bell housing or the clutch department, along with a few of the best methods for troubleshooting these issues so that a professional mechanic can make repairs.

Although the manually operated transmission has evolved considerably over the years, essentially they are still comprised with the same basic components. A clutch system begins with the flywheel which is attached at the back of the engine and is propelled by the crankshaft rotational speed. A drive plate is then attached to the flywheel and supported by a pressure plate.

As the clutch pedal is released, the drive and pressure plates slowly "slip" to apply power to the transmission gear and eventually to the drive axles. Friction between the two plates works in many ways similar to disc brakes. As you press the clutch pedal in, it engages the clutch and stops the transmission input shaft from spinning. This allows you to change gears in the manual transmission to a higher or lower gear-ratio. When you let off the pedal, the clutch disengages, and the transmission is free to spin with the engine.

There are several individual components that make up the clutch system. Operating the clutch requires having working bearings that work together to engage and disengaging (letting off on the pedal) the clutch system. There are several bearings here as well, including the throw out bearing and pilot bearing.

In most cases, when the clutch is showing signs of wearing out; one or several of the above components will have broken or will be worn out prematurely. When these parts wear out, they tend to display a few warning signs that can be used to troubleshoot issues. Noted below are a few of the troubleshooting steps that need to be completed in order to determine what is causing noises coming from the clutch system.

In a modern clutch, the throw out bearing is essentially the heart of the clutch pack. When the clutch pedal is depressed (meaning it's pressed to the floor), this component moves toward the flywheel; applying the pressure plate release fingers. As the clutch pedal is released, the throw out bearing starts to release from the flywheel and engage the clutch system to begin applying pressure to the drive wheels.

Because this component is always moving in and out when you engage the clutch pedal, it makes sense to assume that if you're heading noises as you depress or release the pedal, it's probably coming from this part. In order to troubleshoot the throw out bearing, you'll have to complete the following steps without actually removing the bell housing.

Step 1: Listen for a whining sound as you press the clutch pedal to the floor. If you hear a whining or loud grinding sound coming from underneath your vehicle as you press the clutch pedal down to the floor, it may be caused by a throw out bearing that is damaged and need to be replaced.

Step 2: Listen for sounds as you release the clutch pedal. In some cases, the throw out bearing will make noises as you release the clutch. This is commonly caused by the center bearing grinding on the flywheel as it's moving towards the transmission.

For vehicles that are 4WD or rear wheel driven, a pilot bearing is used in conjunction with the vehicle's transmission to support and keep the transmission input shaft straight as the clutch applies pressure. Although this component may also be included on front wheel drive vehicles, it's typically a RWD component that works as the clutch is disengaged. As you release the clutch pedal, the pilot bearing allows the flywheel to maintain a smooth RPM while the input shaft is slowing and eventually stops. This helps reduce load on the back of the engine. When the part starts to fail, some of the common symptoms will include:

Since this component is vital to the overall operation of the clutch and transmission, if not repaired, it may cause catastrophic failure. Under most circumstances, when the pilot bearing is beginning to show signs of failing, a clunking or high pitched whining sound may be present. It also causes the input shaft to become misaligned, which may also create a sound as the input shaft spins.

Step 1: Listen for sounds as the vehicle is accelerating after the clutch pedal is fully engaged. In most cases, when this part is failing and causing a noise, it will be as the input shaft spins; or after the clutch pedal has been fully engaged or released.

Step 2: Try to feel steering wheel vibrations as it's accelerating. Along with the noise, you may feel a slight vibration (similar to a wheel being out of balance) as the vehicle accelerates and the clutch pedal is fully engaged. This symptom may also be an indicator of other problems; so it's best to contact a mechanic to professionally diagnose the problem if you notice.

Step 3: Smell of rotten eggs. If the clutch pilot bearing is worn out and heating up, it tends to give off a horrible smell, similar to rotten eggs. This is also common with catalytic converters, but you'll notice this more often when you first release the clutch pedal.

Any of the above troubleshooting steps can be completed by a novice DIY mechanic. In order to inspect the component for actual damage, you'll have to remove the transmission and clutch from the vehicle entirely and inspect the part of signs of damage.

The modern "clutch pack" on cars, trucks and SUV's with manual transmissions include several individual parts that work together to produce friction which in turn, applies power to drive axles after sending the power to transmission gears.

The first part of the clutch pack system is the flywheel, which is attached to the back of the engine. On an automatic transmission, the torque converter acts in similar function as the manual clutch. However, its parts are a series of hydraulic lines, and turbine rotors that apply the pressure.

The clutch disc is connected to the back of the flywheel. Then the pressure plate is applied on top of the clutch disc and adjusted by the automotive manufacturer to permit a determined amount of pressure to be applied as the clutch pedal is released. A lightweight housing or cover is then applied to the clutch pack, which keeps dust produced by the burning of clutch discs from spreading into other engine or transmission components.

Sometimes this clutch pack becomes worn out and will need to be replaced. In most production vehicles, the clutch disc is the first to wear, followed by the pressure plate. If the clutch plate is wearing out prematurely, it will also exhibit a few warning sign which may include sounds, noises and even smells similar to the pilot bearing.

Step 1: Listen to the engine RPM as you release the clutch pedal. If the clutch disc is worn out, it will create more friction than it should. This tends to cause the engine RPM to rise as opposed to lowering as the clutch pedal is depressed.

If the engine sounds "weird" while you're releasing the clutch pedal, the most likely source is the clutch disc or the pressure plate that has worn out and needs to be replaced by a professional mechanic.

Step 2: Smell for excessive clutch dust. When the clutch disc or pressure plate is worn out, you'll smell a lot of clutch dust coming from below your vehicle. Clutch dust smells like brake dust, but has a very pungent odor.

The parts that comprise the clutch pack are high wear components and need to be replaced on a regular basis. However, the frequency of replacement will depend on your driving style and habits. When replacing the clutch, it's also very common to have the flywheel resurfaced. This is a job that should be completed by a professional mechanic as clutch adjustment and replacement requires specialized tools and skills that are often taught during technical school or ASE certification training.

In most circumstances, when you notice noise coming from the vehicle as you release or depress the clutch pedal, it's a sign of damage to one of the multiple internal components that make up the clutch pack and clutch system. It may also be caused by other mechanical problems with the transmission such as worn out transmission gears, low transmission fluid or a hydraulic line failure.

Anytime you notice this type of sound coming from below your vehicle, it's a good idea to contact a professional mechanic as soon as possible to complete a loud noise while using the clutch inspection. A mechanic will inspect your clutch operation in order to verify the noise and determine the correct course of action. A test drive may be necessary to duplicate the noise. Once the mechanic has ascertained the cause of the problem, the right repairs can be suggested, a price will be quoted and the service can be completed on your schedule.

A damaged clutch is not only an inconvenience, but it can lead to additional engine and transmission component failure if not repaired as soon as possible. Although in most cases, noises from the clutch are a sign of damaged or worn out parts, finding and replacing these parts before they completely break can save you a lot of money, time and frustration. Contact a professional mechanic to complete this inspection or ask them to rebuild the clutch on your car.

The most popular service booked by readers of this article is Loud noise when using the clutch Inspection. Once the problem has been diagnosed, you will be provided with an upfront quote for the recommended fix and receive $20.00 off as a credit towards the repair. YourMechanics technicians bring the dealership to you by performing this job at your home or office 7-days a week between 7AM-9PM. We currently cover over 2,000 cities and have 100k+ 5-star reviews... LEARN MORE

16 car noises you should not ignore

16 car noises you should not ignore

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Most of us dont even notice these harmless notes after a while. But some noises arent so innocuous. You should not ignore certain thumping, banging, clicking and squealing sounds. These sounds often rear their heads or intensify whenever the driver takes specific actions such as stepping on the accelerator, depressing the brake pedal or turning the steering wheel sharply.

Listen for these noises. If any suddenly becomes part of your everyday driving experience, its time to take action. Something is probably very wrong. Ignoring the symptom wont make the problem magically go away. Delay can provide the time for a problem to worsen, and that usually translates into a bigger and more expensive repair.

Hissing or sizzling under the hood: Heard when the engine is first shut off, something is leaking. Coolant or oil could be leaking onto a heated engine part, such as the exhaust manifold; a vacuum line could be leaking; or the engine could be overheating.

Knocking in engine compartment: Its a myth that there are benefits from using a higher-octane gasoline in your vehicle than the owners manual specifies; however, using a lower-grade fuel can very well produce engine knock. Follow the owners manual requirements in all things oil, gasoline and tire air pressure.

Loud bang: If the sound is as if someone put a cherry bomb in your tailpipe, its a backfire. It could be the air-fuel mixture is too rich. It could also indicate that the catalytic converter isnt functioning properly.

Low-pitch humming or whirring under car: This could have any number of causes. If it changes with acceleration, the differential may need lubricant, the transmission may be failing, the universal joints may be worn or a wheel bearing could be shot. The problem is, the sounds under a vehicle tend to reverberate and echo to the point that its impossible for a lay person to determine the source.

Popping in engine compartment: An array of issues could be responsible, particularly if the sound is accompanied by some engine hesitation. The checklist includes ignition problem, clogged fuel filter, worn or dirty spark plugs, damaged spark plug wires or a compromised catalytic converter.

Roaring that increases with acceleration: The first thing to check is the exhaust system; it could be damaged. Transmission issues could be another cause. In an automatic, perhaps its not advancing to the next gear. With a manual transmission, the clutch could be slipping.

Squealing or chirping on acceleration: This usually indicates a belt or belts are loose and slipping. It could also mean the drive pulley for an accessory such as the water pump has become misaligned.

Squealing wheels when applying brakes: This could have a number of causes from something as simple as dirt on the brake rotors, pads or shoes to something more ominous, such as badly worn pads or shoes. It could also be from a wear-indicator on a pad signaling that it is time for new brake pads. No matter the cause, its a safety issue and requires attention.

Scraping or grinding when applying brakes: If the squealing has turned into scraping, that usually indicates bare metal rubbing against bare metal. The brake pads are shot! Every application of the brake pedal is damaging at least one of the rotors.

Tapping or clicking in engine compartment: The most obvious problem and easiest to remedy is that the engine is low on oil. Check the oil level. If that is OK, the problem could be a loss of oil pressure somewhere in the system. It could also indicate some blockage due to crud in the system. If its not an oil issue, more than likely its related to the valve train. The valves may need adjusting or perhaps the lifters are collapsed.

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critical cooling for gear grinding success | norton abrasives

critical cooling for gear grinding success | norton abrasives

Selecting the correct coolant can provide numerousbenefits. The purpose of using a grinding fluid is toprovide lubrication and cooling that are critical to theeconomical production of precisely ground parts freeof metallurgical defects. Additionally, it lowers abrasivecost by reducing wheel wear, aiding chip evacuation andprotecting the machine from corrosion.

Inconel 718 (IN718) is the most frequently used nickel-based superalloy. Some of the applications of nickel-based superalloys are found in aircraft gas turbines,reciprocating engines, metal processing, space vehicles,heat treating equipment, nuclear power plants, chemicaland petrochemical industries and heat exchangers(Ref. 1).

Components made from this material areeither ground using conventional aluminum oxide basedbonded abrasive grinding wheels or cBN superabrasiveswheels. Grinding is usually performed with agrinding fluid or coolant. In order to provide the necessarylubrication and cooling capacity and achieve partsfree of metallurgical defects while maintaining loweroperating and abrasive costs, grinding fluids are developedwith very complex formulations.

When faced with the problem of selecting the optimal grindingfluid type for grinding a specific work material, it is often very difficultto find quantifiable data on wheel performance and wheel lifeas a function of type of grinding fluid used. There are many typesof grinding fluids available for selection. Chief among these arestraight oils and water soluble oils. Straight oils can be a blend ofone or more of the different base oils (paraffinic, napthenic, syntheticand vegetable) and may contain boundary and/or extreme-pressureadditives such as sulfur, phosphorous or chlorine compounds(Ref. 2).

While these oils provide good lubricity and rust preventionand are easy to maintain, they are also combustible and componentsare left with an oily film that might need to be removed before use.In the case of water soluble oils, the concentrates sold by coolantsuppliers contain 40 percent or more oil and are mixed with water ata ratio of about 5% to 15% to create the metalworking fluid (Ref. 2).

These fluids provide good cooling but due to bacterial growth arenot as easy to maintain as straight oils. The selection of an optimalgrinding fluid type for any operation will vary based on a number ofparameters, including the material to be ground, abrasivetype used, wheel wear, maintenance, disposal andassociated costs.

In order to determine the quantifiable impact ofthe type of grinding fluid on grinding performanceand wheel life, engineers from Norton|Saint-GobainAbrasives did a comparative study at its HigginsGrinding Technology Center inNorthborough, Massachusetts. The results of the study proved thatgrinding IN718 in straight oil gave a 910 timesimprovement in productivity and in wheel life overgrinding in water-soluble oil.

Testing consisted of grinding slots in IN-718 partswith half-inch wide wheels. Two creepfeed grindingmachines were used; one with a water-soluble oil coolant(Trim VHP E812) and the other with straight oilcoolant (Castrol Variocut B27). Wheel speed was constantat 8,500 surface feet per minute and coolant pressurewas 175 psi at a flow rate of 55 gallons per minute.

An engineered, highly porous, ceramic aluminum-oxide-based grinding wheel specification, TG280-H20VTX2, from Norton Abrasives was tested and high-pressurescrubber nozzles were used to keep the wheel face clean.

The TG2grinding wheel used in this test consists of a shaped TG grain madeby replacing post-sinter crushing with a pre-sinter extrusion process(see Figure 1). The resulting needle shaped grains, designated TGand TG2, have extreme aspect ratios (TG = 5:1, TG2 = 8:1). Not onlydo these grains maintain a high toughness, but they also have a verylow packing density. Typical blocky grains will pack to about 50% byvolume whereas the extruded grain with an aspect ratio of 8:1 has apacking density closer to 30%.

Wheels made with this grain have avery high level of permeability/porosity and excellent coolant carryingcapacity. In terms of chip modeling, the high aspect ratio presentsa shape factor comparable to a much larger blocky grain, whichin turn creates a much larger chip and lower specific cutting energy.The combination of all these factors makes the TG family of grainsunusually suited to high stock removal rates when grinding superalloys(Ref. 3).

Testingbegan with straight oil coolant and depth of cut per pass was set at0.100" (2.5 mm). Work speed began at 10 inches per minute andincreased until it reached 180 inches per minute (2544,572 mm/min).

A minimum stock volume of 2 in was removed under eachcondition. With the oil coolant there was never any evidence of burn/thermal damage. Subsequent metallurgical analysis confirmed noburn, and bent grains on the part did not extend more than 0.001"(25 m) below the surface.

The test with WSO coolant began usingthe same 0.100" depth of cut used in the oil test. However, burnoccurred at the first feed rate of 10 inches per minute (254 mm/min). Therefore, an alternate strategy was adopted in which a specificremoval rate was set and work speeds were varied to determine whenburn would occur. To keep the specific removal rate constant, thedepth of cut was decreased as the work speed was increased. Specificremoval rates of 1.0, 2.5 and 3.125 in/min/in (10, 25 and 31 mm/sec/ mm) were chosen and table speeds between 6.1 and 300 inches perminute (2.6 mm/sec 127 mm/sec) were tested.

Figures 3 and 4 show the graphs of specific power and grindingenergy versus volumetric material removal rate. Specific grinding energy, which is defined as the energy required to remove a unit volumeof material, is a measure of the efficiency of the grinding process.There is no difference observed in both these graphs when grindingIN718 with the TG2 wheel in oil vs. water soluble coolant.

Figure 5 shows a graph of G-Ratio vs. Volumetric MaterialRemoval Rate. G-Ratio, which is an indicator of wheel life, was significantlyhigher when grinding in oil coolant. Because rapid wheelwear was observed, it wasnt practical to continue increasing removalrates when grinding in water soluble coolant beyond 5 in/min/in(50 mm/sec/mm). However when grinding with oil coolant, removalrates as high as 18 in/min/in (180 mm/sec/mm) with minimalimpact on G-ratio are possible. This illustrates higher productivity,shorter cycle times and increased wheel life when grinding in oil.

As illustratedin Figure 6, at a constant volumetric stock removal rate, as the workspeed was increased (and depth of cut decreased), the risk ofburn diminished. We would therefore expect that for higher work speeds,the specific grinding energy would be lower. When thinking of thegrinding zone as a moving heat source, as the rate increased, thetime the source is in contact with any point on the part decreases,and thereby limits the amount of heat that is transferred to the part.

Figure 7 shows a graph where the specific grinding energy foreach removal rate is plotted with respect to the work speed, it isclear that the trend for increasing specific grinding energy withdecreasing work speed holds true.

This is due to the fact that, fora given removal rate, as work speed increases and the depth of cutgets smaller, the chip thickness increases. Whereas at lower workspeeds, chip thickness is diminished and more energy is consumedin friction due to plowing and sliding interactions in the grindingzone. It should be noted that this strategy for alleviating burn wasonly used in grinding with water-soluble coolant.

In summary, the results from the comparative test demonstratesthe quantifiable impact of the type of grinding fluid (straightoil coolant, water soluble coolant) on the grinding performanceand wheel life, when grinding IN718 alloy with a modern aluminum-oxide-based ceramic grinding wheel. Both in terms of achievinghigher productivity and wheel life, straight oil coolant outperformswater soluble oil coolant.

However, the actual performanceand G-ratio values will be different for each grinding wheel andwork material combination. Additionally, the reason for certainoperating conditions causing the occurrence of burn on the componentswhen grinding in water soluble coolant versus oil coolantneeds to be investigated with additional testing and thermal modeling,taking into account the dissimilar properties of the two typesof coolant.

Truing and dressing tools are often overlooked until there is a finish, form, or geometric issue, but they are a critical component of the grinding process. Learn why and see how to select the best tool for the job.

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minimizing vibration tendencies in machining |
 

 modern machine shop

minimizing vibration tendencies in machining | modern machine shop

With an overhang of more than 4 times the tool diameter, vibration tendencies can become more apparent and damped tools come into the picture as a good solution.With a damped pre-tuned boring bar machining of holes with a depth of up to 14 times the diameter of the bar can be performed with good results.

Precision internal machining operations are now carried out almost exclusively using hard-metal or diamond tipped cutting tools. Tool holders are available in a variety of forms to suit the specific machining requirements. The material properties of the toolholder have a large influence on both the surface quality and dimensional accuracy of the machined component (workpiece), and on the life of the cutting tool. This becomes critical when machining deep holes, because it is necessary to use a tool with large length to diameter (L/D) ratio or overhang. A high degree of overhang, together with the material properties of the workpiece and various other factors, can lead to excessive vibrations in the tool shaft, which in turn causes undesirable chattering. By the use of passive damping elements, integrated in the tool shaft, the dynamic behavior of the tool can be optimized.

The development within production engineering is accompanied by increasing quality requirements of the produced workpieces. In addition to the product-related high-quality features such as the shape, dimensional tolerances and surface qualities, the effectiveness and controllability of the manufacturing process are relevant factors. As a result of intense development work of the cutting edge, the capability of the cutting tools has been increased considerably.

Seen as a whole, the machine, cutting tool, and workpiece form a structural system having complicated dynamic characteristics. Under certain conditions vibrations of the structural system may occur, and as with all types of machinery, these vibrations may be divided into three basic types:

Free or transient vibrations: resulting from impulses transferred to the structure through its foundation, from rapid reversals of reciprocating masses, such as machining tables, or from the initial engagement of cutting tools. The structure is deflected and oscillates in its natural modes of vibration until the damping present in the structure causes the motion to die away.

Forced vibrations: resulting from periodic forces within the system, such as unbalanced rotating masses or the intermittent engagement of multitooth cutters (milling), or transmitted through the foundations from nearby machinery. The machine tool will oscillate at the forcing frequency, and if this frequency corresponds to one of the natural frequencies of the structure, the machine will resonate in the corresponding natural mode of vibration.

Self-excited vibrations: usually resulting from a dynamic instability of the cutting process. This phenomenon is commonly referred to as machine tool chatter (chatter vibrations) and, typically, if large tool-work engagements are attempted, oscillations suddenly buildup in the structure, effectively limiting metal removal rates.The structure again oscillates in one of its natural modes of vibration.

It is important to limit vibrations of the machine tool structure as their presence results in poor surface finish, cutting edge damage, and irritating noise.The causes and control of free and forced vibrations are generally well understood and the sources of vibration can be removed or avoided during operation of the machine. Chatter vibrations are less easily controlled and metal removal rates are frequently limited because the operator must stop the machine to improve the machining conditions, which often means reducing the depth of cut or feed rate.This article deals with chatter vibrations and how these disturbances can be minimized by the use of damped tools.

The basic cause of chatter is the dynamic interaction of the cutting process and the machine tool structure. During cutting, a force is generated between the tool and workpiece, which acts at an angle to the surface.The magnitude of this cutting force depends largely on the tool-work engagement and depth of cut. The cutting force strains the structure elastically and can cause a relative displacement of the tool and workpiece, which alters the tool-work engagement (undeformed chip thickness). A disturbance in the cutting process (e.g., because of a hard spot in the work material) will cause a deflection of the structure, which may alter the undeformed chip thickness, in turn altering the cutting force. There is a possibility for the initial vibration to be self-sustaining (unstable) and build up, with the machine oscillating in one of its natural modes of vibration.

To make the increased capability of modern cutting edges, the cutting-tool materials available, powerful and stable machine tools, holding tools and cutting tools are required. The shape accuracy of the produced parts is determined by the kinematic machine tool behavior and the static, dynamic and thermal stiffness of the machine tool system. The surface quality that can be achieved depends on the geometry of the cutting edge, the machining parameters and the dynamic behavior of the system: machine tool - cutting tool - workpiece. The metal removing capacity that can be achieved without chatter vibrations is clearly defined by the dynamic machine tool behavior.

For machining complex shapes of dies and moulds, usually tools with a long overhang are used. Equally the machining of the integral components of aircrafts and cars requires the use of tools with a large length to diameter (L/D) ratio. Also for the machining of boreholes and for the inside machining of cylindrical workpieces long boring bars are required.

With increased overhang the tool can become the deciding weak link in the system of machine tool - cutting tool - workpiece. Furthermore, the low static stiffness and material damping characteristics of metallic materials also causes a high dynamic compliance. This can lead to instability of the chip removal process and chatter vibrations.

... are usually derived from chatter vibrations in machining, with cutting tool damage and unsatisfactory workpiece quality. In order to achieve sufficient process stability, the metal removing rate should be reduced or the cutting tool geometry changed. Material substitution as well as geometric shape optimization leads to increased dynamic stability of boring bars. By the use of passive damping elements, integrated in the boring bars, the dynamic behavior of the tools can be optimized.

Generally, machining up to four times the diameter of boring bars does not cause any problems from the vibration point of view, provided that correct conditions apply as regards cutting data and inserts.

There are three different types of damped bars, depending on the length of overhang. Standard bars with a short damping system for machining up to 7 times the bar diameter, standard long bars for machining up to 10 times the bar diameter and cemented carbide reinforced bars (CR bars) for machining up to 14 times the bar diameter.

... made of sintered tungsten carbide or machinable sintered tungsten alloys are an excessively costly solution. In case of a tool collision, a solid carbide bar will snap off in one or more pieces, often with fragments going like projectiles out of the machine tool. Carbide reinforced (CR) bars have some advantages compared to solid carbide bars. A CR-bar is an assembly of carbide rings or sleeves held together by compressive stress from a steel tension bar going through the center of the sleeves. In case of a collision, this will stress the steel parts beyond material yield limit and it will bend away. In a worst case scenario, one or two of the carbide sleeves are also damaged, but these can be replaced at a relatively low price, and the bar can be repaired for a total price which is far less than that of a replacement.

Stability is critical for any machining operation.Vibrations can often be avoided by choosing the right insert, the best standard tool holders, and the right cutting data. An essential part of the service provided by Sandvik Coromant and Teeness, is assisting customers in the application of tools, providing information and training of personnel.

Generally, a solid boring bar will perform adequately in general turning out to 4 times its diameter without vibrations. But in more demanding applications, such as internal threading and grooving, vibrations may start at an overhang between 2 and 3 times the bar diameter. In comparison, the most highly developed bars stretch 15 times beyond their own diameter. Some information on how limits may be stretched using existing tools follows.

A vibration is a variable deflection, thus, no defection means no vibration. Vibrations in a cutting tool are triggered and maintained by a dynamic cutting force. Even in a continuous cut, the cutting force will have small rapid changes in both size and direction around a certain average. The keys to eliminate vibrations are the following: Increase static stiffness, reduce cutting forces, and increase dynamic stiffness.

To increase static stiffness, choose the largest possible diameter for the boring bar and the minimum length. Special bars can also be shape-optimized, for instance be made tapered or elliptic, to utilize all available space in the workpiece. Bars can also be reinforced with materials that are stiffer than steel.

An increased length from 4 to 10 times the bar diameter will give a 16 times larger deflection for a bar taking a constant cutting force.A further extension from 10 to 12 times the bar diameter, gives another 70% increase in deflection from the same cutting force. Holding the bar length constant while changing the bar diameter from 25 to 32 mm, reduces deflection with 62% for equal cutting forces. It is important to cut with sharp edges to minimize the cutting force required to perform the machining operation - a positive cutting geometry reduces cutting forces.

An entering angle close to 90 will direct a maximized feed force in the axial direction of the bar. However, this is not effective unless the nose radius is smaller than the radial depth of the cut. If there is no vibration in the radial direction the boring bar will make a good surface even with small vibrations in the tangential direction.

The smallest acceptable insert point angle will give good clearance of a trailing surface, and small chip area variations if the tool starts vibrating in a radial direction. Reduced weight of cutting units will minimize the kinetic energy in a possible vibration. This will make it easier for the tool to damp possible vibrations, and thus stretch the maximum overhang for both solid and damped tools.

For some machining applications, the above given guidelines are not enough to sufficiently reduce vibration tendencies. These are in many cases regarded as impossible operations, with damped tools being the only option. The choice can sometimes lie between using damped tools or turning away the work, the latter course usually being unthinkable. In addition to better productivity, better surface finish, increased tool-life and better tolerances, the ever increasing higher environmental demands being set in machine shops also creates work for damped tools. Vibration from machining creates noise and sometimes it is necessary to use damped tools to keep within the maximum noise level permitted in a workshop.

The use of damped tools was in the past considered to be exotic and complicated, but this is not the case today. The most critical issue in manufacturing is to perform machining operations in the most efficient way. Today`s damped tooling includes tools that are pre-tuned to the correct frequency in relation to the tool length that is ordered, requiring basically for the damped boring bar and machine to be set up as you would with a conventional, solid boring bar.

Several techniques are known for enhancing dynamic stiffness and stability (chatter-resistance) of long cutting tools and, thus, increasing allowable overhang. The four most widely used and most universal approaches are:

The use of anisotropic bars is based on a theory explaining the development of chatter vibrations during cutting by an intermodal coupling in the two-degrees-of-freedom system referred to the plane orthogonal to the bar axis and passing through the cutting zone. According to this theory there is a specific orientation of stiffness axes relative to the cutting forces, resulting in a significant increase in dynamic stability.

The most frequently used high Youngs modulus materials are sintered tungsten carbide, and machinable sintered tungsten alloy with an added 2-4% of copper and nickel. Both materials are expensive. Solid bars made of both these materials allow stable cutting with ratios L/D < 7.

At present, the commonest approach to enhancing the dynamic stability of long bars is the application of passive dynamic vibration absorbers (DVA) with an inertia mass (pre-tuned bars). The effectiveness of a DVA for a given mass depends on the vibration amplitude at its attachment point. Accordingly, absorbers are usually installed at the furthest available position along the bar. Another factor determining their effectiveness is the mass value of the inertia weight of the DVA. In boring bars, the DVA has to be placed inside the structure. This limits both the position of the DVA along the bar axis and the size of the inertia weight, which has to be positioned in an internal cavity whose diameter must be much smaller than the bar diameter. To achieve a reasonable degree of DVA effectiveness, materials with very high specific density must be used for inertia weights.

If harmonic oscillation (vibration) tendencies should arise during the machining process, the tuning system will immediately come into force, and the kinetic energy of the bar will be absorbed in the tuning system. As a result, vibration is minimized and cutting conditions optimized. It is quite feasible to machine components that require a tool overhang of more than 10 times the tool diameter. Furthermore, with cemented carbide reinforced special bars, overhangs of 14 times the tool diameter can be dealt with successfully.

... are effective, but require vibration sensors and actuators generating forces opposing the deflections of the tool during the vibratory process. The most frequently used are active systems with cavities in the mandrel (bar) body, which are filled with pressurized oil. Pressure values in the cavities vary according to the output of the control system, thus generating dynamic deformations to cancel the chatter vibrations. Present design of active dampers is not very reliable in the shop environment, and may require frequent adjustment.The ultimate L/D ratio for a boring bar with an active damper is 10 12.

The experimental work is a comparative study of the metal removal rate for different types of boring bars at varying L/D ratios performed at SINTEF. Long and slender boring bars for single-point turning are particularly susceptible to self induced vibration. The productivity is traditionally low when using these types of tools.This study includes machining tests with conventional and damped boring bars of steel and tungsten alloy.

With internal tooling the problem of instability is a result of the machining. The only cutting force component which does not need to be counteracted with support is the axial force (Ff) which is directed along the axis of rotation, along the shank of the working bar. The radial cutting force (Fp) bends the tool out and away from the cutting zone in such a way that the diameter of the hole is affected.The tangential cutting force (Fc) bends the tool downwards and away from the center line along which the tool is designed to cut. Poor surface finish is the first sign that the cutting force is not being sufficiently damped.

All the damped boring bars are Sandvik Coromant 570 style produced by Teeness, strong and compact with coolant through center. These bars features the best anti-vibration performance due to minimum weight in front, given by the short distance from the insert tip to damper. The damping system is based on use of passive dynamic absorbers.

In order to minimize the effect of the tool wear on surface roughness and process stability, the inserts were slightly worn by machining 3 min before testing. Each insert was used for maximum 6 min. The depth of cut was corrected for deflection of the boring bars.The surface roughness was measured according to ISO 4288:1998. Two tests were carried out.

A comparative study of workpiece surface roughness for different types of boring bars at varying L/D ratio. The test was performed as a finishing operation with one kind of inserts and appurtenant cutting data.

A comparative study of metal removal rate (productivity) for different types of boring bars at varying L/D ratio. The tests were performed at a constant depth-of-cut to feed ratio. The surface roughness constraint was Ra = 3.6 m.

Damped boring bars can be used up to L/D 13. However, each damped bar has a restricted working area regarding the L/D ratio. It is also shown that the metal removal rate can be sustained up to L/D 12.

The least rigid components of machining systems are long and slender (cantilever) tools and cantilever structural units of machine tools (rams, spindle, sleeves, etc.). These components limit machining regimes due to the development of chatter vibrations, limit tool life due to extensive wear of cutting inserts, and limit geometric accuracy due to large deflections under cutting forces. Use of materials having a high Youngs modulus (such as cemented carbides) to enhance the dynamic quality of cantilever components has only a limited effect and may be costly.

The use of passive vibration absorbers combine exceptionally high dynamic stability and performance characteristics with cost effectiveness.The performance and interaction of these tools were validated by extensive cutting tests with damped boring bars from Teeness. Stable performance with length-to diameter ratios up to L/D = 13 were demonstrated. Comparative tests with similar, commercially available bars from Sandvik Coromant demonstrated the advantages with boring bars featuring passive vibration absorbers, both in surface conditions and productivity.

Teeness is a modern tool manufacturer with 70 employees. Their knowledge about basic metal cutting and mechanical vibrations have made them Sandvik Coromants specialist partner on machining with minimized vibration tendencies. The Teeness office and factory are situated two kilometers west of downtown Trondheim, the third largest city in Norway. All anti-vibration tool adapters from Sandvik Coromant are manufactured at Teeness in Trondheim,Norway. Teeness also manufactures supporting products such as solid adapters and cutting heads for internal turning. Teeness manufactures hundreds of standard Sandvik Coromant products. As partners, the companies team up to support metalworking industries to provide the best solutions.

Demanding applications may require special solutions. Each year Teeness manufactures more than 250 engineered special tools according to specifications from customers around the world.As each one of these makes an impossible operation possible,Together, Sandvik Coromant and Teeness offers customers unique manufacturing advantages.

SINTEF, the Foundation for Scientific and Industrial Research at the Norwegian Institute of Technology, is the largest independent research organization in Scandinavia. SINTEF has 1700 employees and the turnover in 2001 was 232 million Euro. Contracts for industry and the public sector generated more than 90% of this income, while 7% came in the form of basic grants from the Research Council of Norway. SINTEF sells research-based knowledge and related services to Norwegian and international clients. SINTEF collaborates closely with the Norwegian University of Science and Technology (NTNU) and the University of Oslo. Personnel from NTNU work on SINTEF projects, while SINTEF staff teaches at NTNU.The SINTEF-NTNU community involves the widespread joint use of laboratories and equipment. SINTEF is committed to produce high quality deliverables.This means that the products are to be relevant and useful for the clients, maintain high scientific and quality standards, and be presented professionally. If required by clients, SINTEFs quality assurance ensures that the projects meet the requirements of NS-EN ISO 9001 quality standards. Most of the laboratories are accredited according to EN 45001 or the GLP scheme.

solved: why is my washer making a scraping noise when it agitates? - kenmore direct drive washing machine - ifixit

solved: why is my washer making a scraping noise when it agitates? - kenmore direct drive washing machine - ifixit

Washer was working great until we moved, and now ever since then it makes that noise when it is in the agitates? We did not lay it on it's side, we used a dolly to move it to it's new location. I really need the help to fix! Everything else runs fine spins great and filled fine, just happens when it washes the clothes.

had sears repair over today on same problem. ordered belt, cap and bearing going to run $200 to fix. its a maytag thats 8 yrs old and only used 2x per week so motor has a lot of life in it. i'm getting it fixed by sears.

I had this problem, and chased it for a while. The drive pulley nut was too tight, causing this noise (my fault, I had been working on the machine). I backed off a quarter turn, and it's running fine now.

It could be the pump bearing. Tilt the washer back. Look underneath and take the belt off. The pulley on the pump is metal. try turning with your hand both ways. If it grinds that is problem.Sometimes something works it's way into the pump assembly, this will make a clicking or scraping noise. When the motor drive coupler starts to wear down, the washer may also become noisy. Also make sure that there is nothing between the agitator and the tub that could cause it to grind. Make sure your washer is leveled. http://www.justanswer.com/appliance/42wc... mayhelp you as well as http://www.applianceaid.com/direct.html good luck

I had a scraping noise like an old swing chain - it was the top bushing on the suspension rods!- I pulled the front panel- removed the top a little to access the white plastic bushing and used Vaseline in back and a spray lube on the 2 fronts - magic- ps the video on u tube was right on for taking the machine apart - watch it first

I had the same problem after I moved. I found out the cause was when I used a hand truck to move the machine it pushed the thin metal bottom of the machine up just enough to to contact the moving parts making a metal on metal grinding noise. I took the front panel off and pushed the metal back down- problem solved.

Thanks Rene. I had the same issue with my 1 year old GE Hydrowave upright HE washer and we came across this blog and decided to try your solution first after we just moved and had the Sam issue with a scraping noise when the agitator was active. It worked! The bottom was buckeled a little bit and my hubby took the bottom off and pushed it into shape. So far, so good. No more scraping. Thanks!

Thank you so much!!!!! Mine is brand new and was making that metal to metal scraping sound during agitation. And it was from the dent on the bottom plate cause by the hand truck! I am thankful for your advice!!! I don't know why they make the bottom plate so flimsy?!

There is a plastic cap on top of your agitator inside there are plastic "dawgs" that are rigid like a gear which grips the shaft when agitating. anyway they may have been bumped loose.there should be three or four in there. use one of those links that old turkey put in his reply to show you how to replace them.

My lightly used washer was making a noise when the agitator was running, too. I put on a new belt, no help. Then I decided to remove the agitator. I pulled off the softener cup holder, and the bolt holding the agitator was buried in old softener junk. I pushed the socket into it, removed the bolt, and then the agitator. After flushing the agitator a lot in hot water, I turned it upside down and more gunk came out of the bottom. After cleaning for 20 minutes, no more gunk. Reinstalled the agitator, and it fixed the noise! I never could get the agitator apart, but evidently the gunk built up inside the gear and cog system, causing the noise. And the softener will work a lot better too!

top 10 signs of transmission trouble | howstuffworks

top 10 signs of transmission trouble | howstuffworks

Diagnosing car problems yourself may seem like an impossible task, but try to think of it in terms of your own body. For instance, if your stomach begins to hurt without warning, you'll probably start thinking of the last thing you ate in order to figure out why you're having the pain. A similar type of thinking goes into diagnosing car trouble. The moment you start noticing something out of the ordinary, it's time to start considering the problem and finding a way to fix it.

Mechanical auto problems, as opposed to electrical auto problems, are usually coupled with distinct sounds and sensations that are key indicators that something isn't functioning the way it was designed to. Transmissions take a lot of use over the years, and after a while, they're bound to start having some problems. Transmission repairs can be expensive, so it's worthwhile to pay attention to anything that seems unusual.

If you think you may be having some car trouble or if you're just looking to learn more about potential transmission problems, check out these 10 signs of transmission trouble and stay one step ahead of your car.

Despite their somewhat simpler operation, manual transmissions nonetheless have their share of things that can go wrong. One potential problem is that the transmission refuses to budge when you depress the clutch pedal and attempt to move the stick shifter.

It may happen when trying to get into first gear from a stop, or at any point up and down the assorted gears. Common causes include low transmission fluid, wrong viscosity (thickness) of fluid, or required adjusting of the shift cables or clutch linkage.

If you get a whiff of burning transmission fluid, be advised it is definitely not the sweet smell of success. That's because it may indicate your transmission is overheating. Transmission fluid not only keeps the transmission's many moving parts properly lubricated, but it prevents the unit from burning itself up, by providing much-needed cooling.

It seems intuitive that if you hear weird noises when the car should be shifting, that the transmission is acting up. But would you suspect it if things were going "bump" in neutral? Yes, it could be the transmission.

Such sounds could have a simple and inexpensive solution -- as with many of the problems on our list, adding or replacing the transmission fluid sometimes does the trick. Bear in mind that as is the case with engine oil, different vehicles do best with the specific formulation called for in the owner's manual.

Alternatively, lots of noises from the transmission while it's in neutral could signal something more serious, like mechanical wear that will need the replacement of parts. In this case, common culprits are a worn reverse idler gear or worn bearings, possibly coupled with worn gear teeth [source: Procarcare.com].

This is unnerving at best and potentially dangerous at worst: when you mash the gas pedal to avoid an out-of-control vehicle, the last thing you want is a transmission that doesn't get power to the wheels. No need to scratch your head over whether this is trouble or not: if it happens, you know it's time to have your transmission examined.

Here's another transmission trouble sign that haunts manual transmission vehicle owners: the dreaded dragging clutch. A dragging clutch is one that fails to disengage the clutch disk from the flywheel when the driver pushes in the clutch pedal.

When the driver attempts to shift gears, he or she can't because the still-engaged clutch is still spinning along with the engine. The driver is abruptly made aware of this by the grinding noise that then ensues with each attempt to shift.

Fortunately, the most common cause for this problem is not that severe or costly to fix -- at least not compared to some other transmission issues. More often than not, the problem is too much slack in the clutch pedal. With too much free play, the cable or linkage between the pedal and the clutch disk doesn't have enough leverage to disengage the clutch disk from the flywheel (or pressure plate).

Leaking transmission fluid is probably one of the easiest ways to identify that your transmission needs attention. Automatic transmission fluid is vital to your car's shifting capabilities, so a little fluid on your driveway can quickly turn into a major problem. Automatic transmission fluid is bright red, clear and a little sweet-smelling when everything's working correctly [source: AAMCO]. When you check your automatic transmission fluid, make sure it's not a dark color and that it doesn't have a burnt smell. If it is, you'll need to take it to a mechanic and have it replaced. Unlike your car's motor oil, the transmission doesn't really consume or burn up any fluid during use, so if you notice you're running low on fluid, then it's definitely leaking out somewhere.

If you have a manual transmission, checking the fluid levels may not be as easy as simply lifting the hood and reading a dipstick. Manual transmission fluid has to be checked right at the transmission case -- usually through the fill plug. Again, if you suspect your transmission is losing fluid, have a mechanic locate the leak and have it fixed.

If your fluid level is good, there's another easy way to know if there's something wrong with the transmission: go on to the next page to see how you can find out if your transmission is having problems -- without even having to pop the hood.

The check engine light can be a great early indicator that something is starting to go wrong with your transmission. The check engine light can come on for any number of reasons not related to your transmission as well, but don't overlook this clear warning sign.

In newer cars there are sensors throughout the engine that pick up irregularities in the engine and notify the computer that there's something wrong in a particular area. In the case of transmissions, these sensors can pick up vibrations and early problems that you may not even be able to feel or see. If you want to know if your check engine light is telling you about a transmission problem, you can purchase a diagnostic scan tool that you plug into your car underneath the driver's side of the instrument panel. The scan tool will display a code that corresponds to the area of the vehicle causing the fault. If the code tells you there's a transmission problem, well, that's a good time to see your mechanic.

But even if your check engine light isn't on, you can still be on the lookout for transmission problems. On the next page, see what type of movements your car can make when the transmission requires service.

Depending on whether you have a manual or automatic transmission, your car may respond differently when your transmission isn't working correctly. As noted in a previous section, with a manual transmission, a common sign of trouble is a grinding sound or feeling when you shift into a new gear. If you fully engage the clutch, shift and then hear a grinding sound, you may have a worn clutch or you may just need to have it adjusted [source: AAMCO]. Or perhaps one or more of your transmission's gear synchronizers, or synchros, is worn out or damaged. Grinding gears can be caused by a number of different factors.

For automatic transmissions problems, you'll most likely feel the car shimmy into each gear rather than the typical almost unnoticeable shifts, or the transmission will make a jarring transition into the next gear. Both are signs that your transmission needs attention. If you notice anything other than a smooth transition between gears, then you might need to have your automatic transmission looked at for adjustments or repair.

It's difficult to nail down exactly how your car may sound if there's transmission trouble, but one thing's pretty certain, you'll probably get a that-doesn't-sound-right feeling when you hear it. Every car is built differently, so the sounds they produce can vary greatly, but if you have an automatic transmission, there's a good chance you may hear a whining, humming or even a slight buzzing sound [source: Lee Myles Transmissions and Auto Care].

With manual transmissions, the sounds will usually come across as a bit more abrupt and mechanical sounding. If you shift gears and hear a clunking sound, then you definitely need to have it checked out by a professional [source: AAMCO]. But a clunking sound from underneath your vehicle may not always point to a transmission problem. Your constant velocity joints (CV joints), or even your differential may be the culprit [source: AAMCO].

Transmissions are designed to go into the correct gear every time, so when they hesitate or refuse to go, it's a sure sign there's something wrong. With manual transmission problems, you may notice after shifting into a gear that the car's engine will rev up, but the car won't be moving as quickly as the engine is running. In this case, a worn-out clutch or more serious transmission problem may be occurring [source: AAMCO].

Automatic transmissions have the same lack-of-response problem, but will usually manifest the issue while engaging the "Park" or "Drive" selection. The car should shift quickly into either of these modes, but if your transmission hesitates to go into either one, then it's likely there's an issue with the transmission.

troubleshooting - baratza

troubleshooting - baratza

For troubleshooting repair instructions, click on your Baratza grinder below and scroll through our most frequently asked questions to identify and resolve your issue. You can also visit our YouTube channel for step by step technical support videos.

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