Mold in the process of processing, let everyone most vexed is some common defects, these defects will directly lead to the use of the workpiece performance, and even lead to the workpiece can not be used here, so we in the mold processing, must try to avoid some defects, the following seven magic weapons for this problem.

1. Reasonable selection and dressing of grinding wheels. White corundum grinding wheels are better. Its performance is hard and brittle, and it is easy to produce new cutting edges. Therefore, the cutting force is small and the grinding heat is small. Medium grain size, such as 46~60 mesh, is better. Medium soft and soft (ZR1, ZR2 and R1, R2), I .e. coarse grain size and low hardness grinding wheels, good self-excitation can reduce cutting heat. It is very important to choose an appropriate grinding wheel during fine grinding. According to the high vanadium and high molybdenum conditions of mold steel, GD single crystal corundum grinding wheel is more suitable. When processing hard alloy and materials with high quenching hardness, diamond grinding wheel with organic binder is preferred. The organic binder grinding wheel has good self-grinding property and the roughness of the ground workpiece can reach Ra0.2μm. In recent years, with the application of new materials, CBN (cubic boron nitride) grinding wheel shows a very good processing effect, in the CNC molding grinder, coordinate grinding machine, CNC inside and outside the grinding machine finishing, the effect is better than other types of grinding wheel. In the grinding process, attention should be paid to timely dressing the grinding wheel to keep the grinding wheel sharp. When the grinding wheel is passivated, it will rub and squeeze on the surface of the workpiece, causing burns on the surface of the workpiece and reducing the strength.

2, mold processing reasonable use of cooling lubricating fluid, play a cooling, washing, lubrication of the three major role, keep the cooling lubrication clean, so as to control the grinding heat within the allowable range, to prevent the workpiece thermal deformation. Improve the cooling conditions during grinding, such as the use of oil immersion grinding wheel or internal cooling grinding wheel and other measures. The cutting fluid is introduced into the center of the grinding wheel, and the cutting fluid can directly enter the grinding area to play an effective cooling effect and prevent the surface of the workpiece from being burned.

3, the quenching stress after heat treatment is reduced to a minimum, because the quenching stress, network carbonization tissue under the action of grinding force, the tissue phase change is very easy to make the workpiece crack. For precision molds, in order to eliminate the residual stress of grinding, low-temperature aging treatment should be carried out after grinding to improve toughness.

4, the elimination of grinding stress can also be the mold in 260~315 ℃ salt bath immersion for 1.5min, and then at 30 ℃ oil cooling, so that the hardness can be reduced by 1HRC, residual stress reduced by 40% ~ 65%.

5. For precision grinding of precision molds with dimensional tolerances within 0.01mm, attention should be paid to the influence of ambient temperature, and constant temperature grinding is required. From the calculation, it can be seen that for 300mm long steel parts, when the temperature difference is 3 ℃, the material changes by about 10.8μm (10.8=1.2 × 3 × 3, deformation 1.2 μm/℃ per 100mm), and the influence of this factor should be fully considered in each finishing process.

6, the use of electrolytic grinding processing, improve mold manufacturing accuracy and surface quality. During electrolytic grinding, the grinding wheel scrapes off oxide film: instead of grinding metal, so the grinding force is small, the grinding heat is also small, and grinding burrs, cracks, burns and other phenomena will not occur. Generally, the surface roughness can be better than Ra0.16μm; In addition, the wear of the grinding wheel is small. For example, when grinding hard alloy, the wear amount of silicon carbide grinding wheel is about 400~600 of the weight of the ground hard alloy, the amount of wear of the grinding wheel is only 50% ~ 100 of the amount of hard alloy grinding.

7, reasonable selection of grinding amount, the use of radial feed smaller fine grinding method and even fine grinding. If the radial feed and grinding wheel speed are appropriately reduced, and the axial feed is increased, the contact area between the grinding wheel and the workpiece is reduced, and the heat dissipation conditions are improved, so as to effectively control the increase of the surface temperature.