The secret of dressing grinding wheels

An operator with high-quality dressing tools and proficient dressing skills can always maintain the high grinding performance of the grinding wheel. Instead of just relying on buying so-called good grinding wheels. This is very important because the workshop cannot be equipped with special grinding wheels according to the operation of each person.

Sharpening is a process of sharpening the abrasive grains of super-hard abrasive wheels. In this process, it is necessary to remove the bond between the abrasive grains and the blunt grinding wheel abrasive grains, so that the grinding wheel abrasive grains with strong grinding performance protrude beyond the bond to form a sharp cutting edge. Sharpening must also remove tiny materials from the pores on the surface of the grinding wheel to prevent the increase of the grinding force acting on the grinding wheel. The increase of the grinding force on the grinding wheel will cause vibration and cause surface burns.

Without proper sharpening, even the best grinding wheels cannot obtain the high quality and dimensional consistency of the machined parts. In fact, when you invest in high-quality grinding wheels, in order to obtain high grinding performance, it is very important to dress them well.

Shaping can be said to be part of the preparation of the grinding wheel, which is carried out at the same time as the sharpening of the ordinary grinding wheel. For super-abrasive grinding wheels, the two processes are carried out separately. First, the grinding wheel is reshaped. In grinding with super-abrasive grinding wheels, shaping is carried out using shaping tools or rollers. Shaping often uses a dressing rod with a ceramic bond. After shaping is completed, the grinding wheel is sharpened.

Before the dressing of the grinding wheel includes shaping and sharpening, it is important to ensure that the spindle bearing is at a certain temperature (such as the usual grinding wheel grinding state). This can avoid damage to the geometry of the parts and abnormal wear of the grinding wheel and dressing tools. The tools used for dressing must be handled carefully, because they are generally made of hard, wear-resistant but very brittle diamond material, and are very sensitive to small cracks and breakage caused by slight collisions and force.

Because the diamond shaper itself is a tool, it needs to be very sharp. Using a dull dressing tool to dress the surface of the grinding wheel will make the grinding wheel dull. In order to maintain a high-quality and sharp diamond dressing tool, it is necessary to rotate a single-point or tapered dressing tool in 1/8 circle at regular intervals. The number of rotations can be determined according to the dressing situation, and based on experience, at least once a day. For chisel heads and shaped dressing tools, they generally need to be rotated 180° once before they are dulled.

Most cylindrical grinding machines place the parts and the grinding wheel on a horizontal line. The highest point of the outer circle of the part and the highest point of the outer circle of the grinding wheel is called the part/grinding wheel contact point. The diamond dressing tool should be as close as possible to the part/grinding wheel contact point to dress the grinding wheel. For grinding wheels for internal grinders, it is more important to dress the diamond dressing tool close to the highest point of the outer circle of the grinding wheel (that is, the contact point of the part/grinding wheel during hole grinding).

Minor trimming

In order to reduce the trimming time, there seems to be a temptation to choose a larger trimming depth. This is an extremely wrong idea. The most suitable dressing depth must be selected to dress the grinding wheel. Choosing a too large dressing depth will produce high cutting temperature, reduce the service life of the dresser, and also remove useful grinding wheel layers. The end result is damage to both the dresser and the grinding wheel, which is counterproductive. The best dressing amount is that after several trimmings, it can restore the geometry of the grinding wheel and just produce a good grinding edge.

Use a single-point dressing tool to contact the diameter direction of the grinding wheel with an inclination angle of the axis line of 10-15°. This will cause the single-point dressing tool to have a sharpening effect when it rotates regularly. Dressing tools with multiple contact points do not need to be tilted at this angle. Instead, use the entire end face of the dressing tool to contact the surface of the grinding wheel.

The lateral movement speed is the speed at which the dressing tool passes through the surface of the grinding wheel during dressing. It plays a key role in the surface roughness and metal removal rate required for machined parts. If the lateral movement speed is too slow, it will block the grinding wheel and damage the surface roughness and metal removal rate of the parts. Too slow lateral movement speed can also cause the grinding wheel to vibrate and burn the surface of the part. The uniform and fast lateral movement speed can dress a good grinding wheel surface, improve the grinding performance of the grinding wheel, increase the grinding efficiency, and reduce the surface roughness of the parts.

Keep it cool

Appropriate use of coolant can speed up dressing and improve dressing efficiency. According to experience, choosing a 3/8 inch diameter coolant can remove a lot of heat from the dresser and prolong the service life of the dresser. When the diamond dressing tool passes through the grinding wheel, install a coolant nozzle to fill the entire surface of the grinding wheel or continuously add coolant to the diamond dressing tool. When the dressing tool contacts the grinding wheel and starts dressing, never allow the dressing tool to withdraw from the coolant. Otherwise, the diamond dressing tool will crack or break under the extreme temperature changes of cold and heat.

The use of a filter to filter the coolant with high precision can avoid multiple cycles of dirt or chips in the coolant. Contaminated coolant can quickly wear the grinding wheel and increase the number of dressings of the grinding wheel. Only during dry grinding (only in this case, the cooling of the diamond dressing tool can be interrupted), the dry dressing of the grinding wheel is adopted. Before leaving get off work every day, after turning off the coolant, let the grinding wheel idle for a few minutes. This prevents the grinding wheel from cracking.

Vibration is the enemy of dressing

In the dressing of the grinding wheel, it is very important to effectively reduce the vibration and avoid leaving dressing marks, collisions and damage to the dressing tools on the surface of the grinding wheel. This means that the balance of the grinding wheel must also be maintained, which is determined by the structural characteristics of the grinding wheel itself. The uneven density and the geometry of the entire grinding wheel will affect the inherent balance of a grinding wheel. Therefore, choosing a high-quality grinding wheel is also very important.

If it is a high-quality grinding wheel, only proper installation can keep the grinding wheel in good balance. According to the factory instructions of the grinding wheel manufacturer, the grinding wheel is marked with an upward arrow, which indicates the light end position of the grinding wheel after rough balance. Then the user can follow the arrow indication and pay attention to dressing the grinding wheel to achieve dynamic balance. The even filling of coolant can sometimes help the grinding wheel to maintain balance.

In order to further avoid vibration, it is necessary to ensure that the dressing tool is firmly clamped on the clamp base and the amount of overhang is kept to a minimum to ensure that the dressing tool has sufficient rigidity. If the diamond tool is not firmly clamped, it will cause vibration, noise, ripples on the surface of the part, strain the surface of the part and damage the dressing tool.