How to reduce defects in plastic mold processing


1. Reasonable use of cooling lubricating fluid plays th […]

1. Reasonable use of cooling lubricating fluid plays the role of cooling, cleaning and lubrication, keeping cooling and lubrication clean, so as to control the grinding heat within the allowable range and prevent thermal deformation of the workpiece. Improve the cooling conditions during the grinding process, such as using oil-immersed grinding wheels or internally cooled grinding wheels. The cutting fluid is introduced into the center of the grinding wheel, the cutting fluid can directly enter the grinding area, which has an effective cooling effect and prevents burns on the surface of the workpiece.

2. Reduce the quenching stress after heat treatment to a minimum, because the quenching stress and the network carbonized structure are easy to produce cracks in the workpiece due to the phase change of the structure under the action of the grinding force. For high-precision molds, in order to eliminate the residual stress of grinding, low temperature aging treatment should be carried out after grinding to improve toughness.
3. In order to eliminate the grinding stress, the mold can also be immersed in a salt bath of 260~315℃ for 1.5min, and then cooled in 30℃ oil to reduce the hardness by 1HRC and the residual stress by 1HRC. Reduced by 40%~65%.
4. 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. It can be seen from the calculation that for a 300mm long steel, when the temperature difference is 3°C, the material change is about 10.8μm (10.8 = 1.2×3×3, the deformation per 100mm is 1.2μm/°C). Every finishing process needs to fully consider the influence of this factor.
5. Electrolytic grinding is used to improve the manufacturing accuracy and surface quality of the mold. In the electrolytic grinding process, the grinding wheel will scrape the oxide film: instead of grinding metal, the grinding force is smaller, the grinding heat is also smaller, and there will be no burrs, cracks, burns, etc. The general surface roughness can be better than Ra0.16μm; in addition, the wear of the grinding wheel is very 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. When electrolytic grinding is used, the wear of the grinding wheel is only 50% to 100% of the grinding amount of cemented carbide.