What should be paid attention to when polishing zinc alloy die castings?

Before mechanical polishing, the quality of die casting must be checked first. Because improper mold design and casting process will lead to surface defects, such as cracks, subcutaneous bubbles, pores, cracks and other defects, which is a potential source of corrosion and one of the main factors affecting the quality of coatings. Before mechanical polishing, the quality of die casting must be checked first. Because improper mold design and casting process will lead to surface defects, such as cracks, subcutaneous bubbles, pores, cracks and other defects, which is a potential source of corrosion and one of the main factors affecting the quality of coatings. If the die casting quality is unqualified, it is not allowed to enter the polishing process. The surface is required to be smooth, dense and flat, without cold lines and pores.

When polishing, attention should be paid to the characteristics of fine surface layer and loose internal structure of die casting. If the dense layer on the surface is thrown away and the loose layer is exposed, there will be more polishing and roughening phenomena, which will seriously affect the adhesion of the electroplated layer and the hardness of zinc alloy will be low. Therefore, grinding wheels should be avoided as far as possible for zinc die castings. If the surface of the workpiece is rough, it is necessary to polish the silk flow and scars. It is advisable to use a grinding wheel with a lower rotation speed (1200 ~ 1400 r/min) and a smaller diameter (≤250mm). Do not use too much force during operation and do not throw away the dense layer on the surface. When polishing the cloth wheel, it is necessary to select the appropriate rotation speed (1400 ~ 1800 r/min), the material of the polishing wheel (fine cloth or felt wool) and the diameter of the polishing wheel (≤300mm). If the rotating speed is too fast, the force is too strong, and there is a lack of polishing paste on the polishing wheel, tiny pits and wrinkles that are difficult to distinguish with the naked eye will be formed on the surface of the parts, which will not only affect the decoration, but also cause blistering and peeling. When operating, pay attention to throwing and putting down gently, and the polished parts should be electroplated as soon as possible, which will affect the appearance and adhesion of the coating if it is left for too long.