The grinding wheel is a special tool, because the working speed of the grinding wheel is very high, and the grinding wheel is brittle. If the installation is not correct, the grinding wheel will lose balance and cause vibration, which will affect the processing quality and machine precision. In severe cases, the grinding wheel may break and fly out. And caused a serious accident.
1 Grinding wheel installation method
(1) Step flange mounting wheel: For parallel grinding wheel with larger hole diameter, the grinding wheel is first clamped between the two flanges with nuts and screws, and then mounted on the outer vertebral body of the grinding wheel spindle. The nut is fastened.
(2) Flat flange clamping wheel: For parallel grinding wheel and bowl wheel with not too large diameter, use the flat flange and washer to clamp the grinding wheel directly on the grinding wheel spindle or the long shaft.
(3) Long shaft clamping: For grinding wheels with a small diameter (less than 20mm).
(4) Sulfur bonding clamp is suitable for cylindrical grinding wheel.
2 Wheel installation and disassembly
Pay attention to the following when installing and removing the grinding wheel:
(1) Before installing the grinding wheel, check the grinding wheel for cracks. The common method is to lift the grinding wheel and gently tap the side of the grinding wheel with a wooden handle. If the sound is clear, it means that the grinding wheel has no cracks. If the sound is "dumb", the grinding wheel has cracks.
(2) The inner hole of the grinding wheel should be matched with the long shaft and the flange, etc., and there should be a proper gap to avoid the thermal expansion of the grinding wheel and the grinding wheel to be cracked.
(3) When the grinding wheel is clamped by the flange, the diameters of the two flanges must be equal. Their size should not be less than one third of the outer diameter of the grinding wheel. The inner part of the inner end of the flange should be dug out. The annular groove is 2~3mm deep, so that only one annular surface of the outer edge is in contact with the grinding wheel to ensure the clamping is stable, and the end face of the flange contacting the grinding wheel must be straight.
(4) Between the flange, the washer and the end face of the grinding wheel, a gasket made of elastic material such as cardboard or oil-resistant rubber should be placed to make the pressure distribution even when the flange and the gasket are pressed tightly, so as not to damage the grinding wheel. The thickness of the gasket may be between 0.5 and 1 mm and its diameter should be slightly larger than the diameter of the flange or gasket.
(5) When tightening the flange, the nut cannot be tightened too much, otherwise the grinding wheel will break. When tightening the flange with several screws, tighten the screws gradually in a diagonal order. When tightening the screws, use only a standard wrench, instead of using a long spanner or tapping to increase the tightening force.
(6) When the grinding wheel flange is mounted on the grinding machine spindle, the cone hole of the flange and the cone of the grinding machine spindle must be wiped clean to ensure the concentricity of the grinding wheel and the main shaft.
(7) When the new grinding wheel is loaded onto the grinding machine for the first time after being balanced, it must be idling for 1 to 3 minutes with the protective cover. At this time, the operator must stand on the side of the grinding wheel to prevent accidents.
3 Balance and dressing of the grinding wheel
There are many factors that cause the wheel to be unbalanced: the geometry of the grinding wheel is asymmetrical, the end faces are not parallel, the outer circle is not concentric with the hole, the organization of the grinding wheel is uneven, the wheel is eccentric during clamping or the uneven wear of the grinding wheel during grinding Wait. When the unbalanced grinding wheel rotates at a high speed, the centrifugal force that forces the grinding wheel to deviate from the axial line is generated, causing vibration of the machine tool, causing the spindle bearing to wear rapidly, causing vibration on the surface of the workpiece to be processed, increasing the roughness of the surface, and even causing the grinding wheel to rupture. Causing personal equipment accidents.
3.1 Static balance of the grinding wheel
Three-point balance method:
(1) Firstly arrange the three balance blocks with the serial number at 120° intervals in the annular groove of the flange, and fix the balance block to prevent sliding.
(2) Install the flange of the mounted grinding wheel on the balance mandrel, place it on the parallel axis of the balanced balance bracket, and make the axis of the balance mandrel perpendicular to the axis of the two parallel axes. .
(3) Then turn the grinding wheel so that the first balance weight is at the highest point. If the grinding wheel is deflected to the left or right, move the adjustment weight to the right or left until the grinding wheel is stationary, and then tighten the balance weight.
(4) Rotate the grinding wheel through 120°, so that the second balancing block is at the highest point. Adjust the position of the balancing block in the same way, and then tighten the balancing block after the grinding wheel is stationary.
(5) Then rotate the grinding wheel through 120° to make the third balance block at the highest point. In the same way, the grinding wheel is stationary and the balance weight is tightened.
(6) Finally, gently move the grinding wheel by hand. If the grinding wheel can be stopped at any position, the grinding wheel is well balanced.
3.2 grinding wheel dynamic balance
The method of static balance can only balance the various parts of the grinding wheel in the non-use state, and the dynamic imbalance will occur after the grinding wheel rotates at high speed in the working state. The dynamic imbalance of the grinding wheel will cause vibration, reducing the grinding quality and the life of the grinding wheel. When the dynamic balancer or balancing device is installed on the grinding wheel main shaft, the unbalanced state of the grinding wheel can be continuously detected and compensated during the rotation of the grinding wheel, so that the grinding wheel is always in a good balance state.
Dynamic balance mode: power consumption type, electromagnetic force type, weight loss type, counterweight type.
3.3 dressing of the grinding wheel
During the grinding process, due to friction and other reasons, the abrasive grains on the working surface of the grinding wheel will gradually become dull. After the grinding wheel is blunt, the grinding force will increase, the grinding temperature will rise, and the flutter and burn will occur, so that the surface integrity of the machined parts will be affected. Great impact. At the same time, the blunt grinding of the grinding wheel will also cause the surface of the grinding wheel workpiece to lose the correct geometry and reduce the machining accuracy. Therefore, in order to maintain the correct shape and sharpness of the grinding wheel during use, it is necessary to regularly dress the grinding wheel.
Grinding wheel correction method
1. Diamond dressing: Diamond dressing is a method in which diamond is used as a tool, that is, a large-grained diamond is welded on a special arbor and a grinding wheel is used to trim the grinding wheel. When dressing the grinding wheel, the diamond arbor is placed in a special dresser on the grinding machine and trimmed with a longitudinal pass. Due to the extremely high hardness of the diamond and the sharp edges and corners, the grinding wheel can be trimmed correctly and carefully, and high machining precision and very fine surface roughness can be obtained.
2, diamond pen trimming: diamond pen is made of small particles of diamond or diamond powder combined with a strong bonding alloy, pressed into a special metal arbor. There are many factors that affect the quality of the dressing when trimming the grinding wheel with a diamond pen, such as the shape of the diamond's cutting edge, the wear resistance of the diamond, the dressing parameters (dressing feed, grinding wheel dressing speed, dressing depth), dressing device, grinding wheel characteristics (abrasive type) , hardness, particle size, structure, binder) and grinding fluid.
3. Roller cutter trimming: It is only used for the general dressing of the grinding wheel, and should not be used for the finishing of fine grinding or fine grinding wheel. When trimming, it is generally done by hand, so that the roller piece contacts the surface of the grinding wheel and is properly moved for trimming. When the surface roughness of the workpiece is required to be low, the tool holder should be placed in a special dresser for the grinding machine to be trimmed to reduce vibration.
4. Dressing of silicon carbide grinding wheel block: The grain size of the silicon carbide grinding wheel block is 2~3 grades than the grinding wheel, and the hardness is 1~2. Manually operating during dressing, the grinding wheel block is slowly moved along the busbar on the surface of the grinding wheel. This trimming function is used for roughing and then trimming with diamond.
4 Safe use of the grinding wheel
Safe use of the grinding wheel includes safe speed, installation and operation, safety protection, transportation and storage.
4.1 Transportation and storage of grinding wheels
(1) Long-distance transportation should be properly packed in wooden boxes or wicker baskets, and the grinding wheels should be separated by soft materials such as straw and sawdust to place collisions and impacts.
(2) The grinding wheel of the ceramic bond should not be placed in a wet or frozen place. The grinding wheel of the rubber bond should not be in contact with the oil. The grinding wheel of the resin bond should not be in contact with the alkali, otherwise the strength and grinding force of the wheel will be reduced.
(3) The grinding wheel should be stored in a dry place at room temperature not lower than 5 °C.
(4) Grinding wheels with large diameter or thicker should be placed upright and slightly inclined. Thinner and smaller grinding wheels should be placed flat, but should not be too high, and a flat iron plate should be placed on top of each other. Or rupture.
4.2 Safety protection during grinding
The safety guard on the grinding machine is mainly a protective cover. Once the grinding wheel is broken, the protective cover of the grinding wheel should have sufficient strength and reasonable structure to prevent the fragments from flying, resulting in personal and equipment accidents. The protective cover is generally welded with A3. When the diameter of the grinding wheel is less than 40mm and the width is less than 50mm, and the grinding wheel speed is below 34m/s, the circumferential wall thickness of the protective cover is not less than 5mm, and the thickness of the two side walls is not less than 4mm. Under the premise of not affecting the grinding of the grinding wheel, the opening of the casing should be reduced as much as possible to reduce the chance of the grinding wheel fragments flying out from the opening and reduce the scattering surface when the pieces fly out. When dressing the grinding wheel, care should also be taken to prevent the wear debris and sand and the splashing of the grinding fluid and the formation of water mist, which affects the operator's health and causes environmental pollution.