Mold in the process of processing, let us most worry about some common defects, these defects will directly lead to the performance of the workpiece, and even lead to the workpiece can not be used in this, so we are in mold processing, must try to avoid some defects, the following for this problem to provide seven magic weapons.
1, the reasonable choice and dressing grinding wheel, using white corundum grinding wheel is better, it is the performance of hard and brittle, and easy to produce the new cutting edge, so the cutting force is small, the grinding heat is small, use medium granularity on granularity, such as 46 ~ 60 mesh is better, on the grinding wheel hardness by using soft and soft (ZR1, ZR2 and R1, R2), namely, coarse granularity, low hardness of the grinding wheel, Good self excitation can reduce cutting heat. Of selecting the appropriate fine grinding wheel is very important, in view of the condition of the die steel with high vanadium high molybdenum, choose GD is suitable for single crystal corundum grinding wheel, when processing hard alloy, high quenching hardness of materials, the priority of using organic binder of diamond grinding wheel, since the organic binder grinding wheel grinding, grinding the workpiece roughness of Ra0.2 mu m, in recent years, With the application of new materials, CBN (cubic boron nitride) grinding wheel shows very good processing effect. It is superior to other kinds of grinding wheel in finishing machining on CNC forming grinder, coordinate grinder and CNC internal and external grinding machine. 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 slip and rub on the surface of the workpiece, resulting in surface burns and reduced strength.
2, mold processing reasonable use of cooling lubrication fluid, cooling, washing, lubrication of the three roles, keep the cooling lubrication clean, so as to control the grinding heat within the allowable range, to prevent thermal deformation of the workpiece. Improve the cooling conditions during grinding, such as using oil-sand wheel or internal cooling grinding wheel and other measures. By introducing the cutting fluid into the center of grinding wheel, the cutting fluid can directly enter the grinding zone to play an effective cooling role and prevent the workpiece surface from being burned.
3, the quenching stress after heat treatment is reduced to the minimum, because the quenching stress, network carbonization structure under the action of grinding force, the structure of phase transformation is easy to crack the workpiece. In order to eliminate the residual stress of grinding for precision die, low temperature aging treatment should be carried out after grinding to improve toughness.
4, eliminate grinding stress can also be the mold in 260~315℃ salt bath soak 1.5min, and then cool in 30℃ oil, so that the hardness can be reduced by 1HRC, residual stress reduced by 40%~65%.
5. For precision grinding of precision die with size tolerance within 0.01mm, attention should be paid to the influence of ambient temperature and constant temperature grinding is required. According to the calculation, when the temperature difference is 3℃, the material changes about 10.8μm (10.8=1.2×3×3, the deformation per 100mm is 1.2μm/℃), and the influence of this factor should be fully considered in all finishing processes.
6, using electrolytic grinding processing, improve mold manufacturing accuracy and surface quality. In electrolytic grinding, the grinding wheel scrapes the oxide film instead of grinding the metal, so the grinding force is small, the grinding heat is small, no grinding burrs, cracks, burns and other phenomena, the general surface roughness can be better than Ra0.16μm; In addition, the wear of grinding wheel is small, such as hard alloy grinding, the wear of silicon carbide grinding wheel is about 400%~600% of the weight of hard alloy grinding off, when grinding with electrolysis, the wear of grinding wheel is only 50%~100% of the hard alloy grinding.
7, reasonable selection of grinding dosage, the use of small radial feed grinding method or even fine grinding. If the radial feed and grinding wheel speed are properly reduced and the axial feed is increased, the contact area between grinding wheel and workpiece is reduced and the heat dissipation condition is improved, so as to effectively control the increase of surface temperature.