In order to improve the performance of the mould, many […]
In order to improve the performance of the mould, many manufacturers will properly process their moulds. mould processing refers to the processing of forming and blanking tools. In addition, it also includes shearing moulds and die-cutting moulds. However, in many cases, the moulds are processed. It will also reflect processing defects, resulting in a decline in mould performance. How to build mould processing defects? The following seven measures can build mould processing defects.
1. Reasonably select and dress the grinding wheel. The grinding wheel of white corundum is better. Its performance is hard and brittle, and it is easy to produce new cutting edges. Therefore, the cutting force is small, the grinding heat is small, and the medium particle size is used, such as 46~60 mesh is better. Medium soft and soft (ZR1, ZR2 and R1, R2) are used in the hardness of the grinding wheel, that is, coarse-grained, low-hardness grinding wheels. Good self-excitation can reduce cutting heat. It is very important to choose an appropriate grinding wheel during fine grinding. For the high vanadium and high molybdenum condition of the mould steel, GD single crystal corundum grinding wheel is more suitable. When processing cemented carbide and materials with high quenching hardness, the organic binder diamond is preferred. Grinding wheels, organic binder grinding wheels have good self-grinding properties, and the roughness of the ground workpieces can reach Ra0.2μm. In recent years, with the application of new materials, CBN (cubic boron nitride) grinding wheels have shown very good processing results. Finishing on CNC forming grinder, coordinate grinder, CNC internal and external cylindrical grinder, the effect is better than other types of grinding wheels. In the grinding process, attention should be paid to dressing the grinding wheel in time to keep the grinding wheel sharp. When the grinding wheel is passivated, it will slip and squeeze on the surface of the workpiece, causing burns on the surface of the workpiece and reducing its strength.
2. Reasonably use cooling lubricating fluid, play the three roles of cooling, washing and lubrication, keep cooling and 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 the use of oil-immersed grinding wheels or internal cooling grinding wheels. Introduce the cutting fluid into the center of the grinding wheel, the cutting fluid can directly enter the grinding area, play an effective cooling role, and prevent burns on the surface of the workpiece.
3. Reduce the quenching stress after heat treatment to a minimum, because the quenching stress and the net-like carbonized structure under the action of the grinding force, the phase change of the structure can easily cause the workpiece to crack. For high-precision moulds, in order to eliminate the residual stress of grinding, low temperature aging treatment should be carried out after grinding to improve toughness.
4. To eliminate the grinding stress, the mould can also be immersed in a salt bath at 260~315℃ for 1.5min, and then cooled in 30℃ oil, so that the hardness can be reduced by 1HRC and the residual stress can be reduced by 40%~65%.
5. For precision grinding of precision moulds with dimensional tolerances within 0.01mm, attention should be paid to the influence of ambient temperature, and constant temperature grinding is required. It can be seen from the calculation that for a 300mm long steel, when the temperature difference is 3°C, the material will have a change of about 10.8μm (10.8=1.2×3×3, the deformation per 100mm is 1.2μm/°C), and each finishing process needs to be fully considered The influence of this factor.
6. Electrolytic grinding is used to improve mould manufacturing accuracy and surface quality. During electrolytic grinding, the grinding wheel scrapes off the oxide film: instead of grinding the metal, the grinding force is small, the grinding heat is also small, and there will be no grinding burrs, cracks, burns, etc., and the general surface roughness can be better than Ra0 .16μm; In addition, the wear of the grinding wheel is small, such as grinding cemented carbide, the wear of the silicon carbide grinding wheel is about 400% to 600% of the weight of the cemented carbide that is ground. When electrolytic grinding is used, the wear of the grinding wheel The amount is only 50%~100% of the grinding amount of cemented carbide.
7. Reasonably choose the amount of grinding, adopt a fine grinding method with a small radial feed amount or even fine grinding. If the radial feed rate and the grinding wheel speed are appropriately reduced, and the axial feed rate is increased, the contact area between the grinding wheel and the workpiece is reduced, and the heat dissipation conditions are improved, thereby effectively controlling the increase in surface temperature.