The essence of the grinding process of plastic bottle cap mold is that the workpiece is grinded on the metal surface, which deforms under the instant extrusion and friction of numerous abrasive particles, and then turns into abrasive particles, forming a smooth surface. The whole process of grinding is represented by the effect of force and heat. What is the impact on the plastic bottle cap mold during the grinding process?

① in the process of grinding, the machined surface will generate thermal expansion under the action of cutting heat. At this time, the temperature of the base metal is relatively low. Therefore, the surface will generate thermal compressive stress. When the grinding is finished, the surface temperature of the workpiece will decrease. Because the surface has generated thermal plastic deformation and is limited by the base, the surface will generate residual tensile stress and the inner layer will generate residual compressive stress

② during grinding, the grinding wheel and the workpiece are in arc contact. During grinding, the workpiece produces plastic deformation and violent friction resistance between the grinding wheel and the workpiece, thus forming grinding force with equal size and opposite direction between the grinding wheel and the workpiece. At the same time, due to the plastic deformation of the surface material, the relative displacement between the metal molecules inside the workpiece material occurs, forming internal friction and heating, and external friction between the grinding wheel and the workpiece It also generates heat. This grinding heat will generate a local instantaneous high temperature of 1000 ℃ in the grinding area, while the grinding wheel is not easy to heat transfer, so 80% of the heat is transferred to the workpiece and grinding debris, while the metal in the solid state changes from one kind of lattice to another with the change of temperature, resulting in the transformation of metallographic texture. When grinding hardened steel, the cooling is sufficient, the surface layer produces secondary quenching, and some residual austenite is transformed into Martensite, but the specific volume of martensite is larger, the specific volume increases, and the surface produces pressure stress. If the grinding cooling is not good, or if the coolant is not used, the surface produces tempering, and martensite transformation occurs, and the surface produces tensile stress (for example, the volume of iron will expand by 1% when γ Fe is transformed into α - Fe). These stresses (residual stress can reach 500-1000mpa). If the yield limit of the material is exceeded, grinding cracks will be produced. In addition, heat treatment will be carried out After quenching, the mould is not tempered immediately, the quenching temperature is too high, there is network carbonization, there are too many martensite or retained austenite which are not tempered after tempering, the transformation will occur during grinding, and the stress will cause cracks on the surface of the workpiece. The grinding crack is a very fine surface crack, and there are generally three kinds of grinding crack forms: parallel line, network crack and splayed crack. The direction of crack occurrence and the mould The development direction of the crack is related to the grinding direction of the grinding wheel on the workpiece surface, and its depth is within 0.03mm

③ when grinding, the grinding wheel is not sharp, the feed amount is large, and the cooling is poor, which makes the temperature on the workpiece surface reach 300 ℃, causing the burn phenomenon on the workpiece surface

There is a little bit of improper grinding process, will make plastic bottle cap mold production of workpiece damage.