The surface polishing process of die casting mold has a direct and important impact on the surface finish of castings. The two are closely related and jointly determine the appearance quality and performance of die casting products.
First, the roughness of the mold surface is the basic factor affecting the surface finish of castings. Through different polishing processes, the roughness of the die casting mold surface can be reduced to different degrees. For example, the multi-level polishing process combining rough polishing, medium polishing and fine polishing can gradually remove the processing marks and micro-roughness on the mold surface, so that the mold surface can achieve a higher finish. When the molten metal fills the mold cavity during the die casting process, the smoother the mold surface, the smaller the resistance of the molten metal flow, and the cavity can be filled more evenly, so that the surface of the casting is smoother and smoother, replicating the smooth effect of the mold surface.
Secondly, the polishing process can improve the microstructure of the mold surface, thereby affecting the surface quality of the casting. A suitable polishing process can form a dense and uniform micro-texture on the mold surface, which can guide the flow direction of the molten metal to a certain extent and reduce the generation of turbulence and eddy currents. During the die casting process, the orderly flow of molten metal helps to avoid gas inclusions and the formation of oxide scale, making the surface of the casting more dense and smooth, reducing the appearance of surface defects such as pores and pitting, and significantly improving the surface finish of the casting.
Furthermore, the glossiness of the mold surface is also one of the important factors affecting the appearance of the casting, and the polishing process is the key means to control the glossiness of the mold. Different polishing materials and methods can give the mold different glossiness. For example, fine polishing with diamond abrasive paste can make the mold surface have a higher mirror gloss. When a mold with good glossiness is die-casted, the surface of the casting produced will also show a similar gloss effect, so that the casting has better appearance quality and meets the needs of some products with high appearance requirements, such as automotive parts, electronic product housings, etc.
Finally, it should be noted that the selection and implementation of the die casting mold surface polishing process must be comprehensively considered based on specific die casting process parameters, casting materials and shapes. Excessive polishing may cause the mold surface to form an overly smooth "mirror", which is not conducive to the adhesion and solidification of the molten metal and affects the quality of the casting. Therefore, through a lot of experiments and practices, the most suitable polishing process parameters should be found to achieve the best match between the surface finish of the die casting mold and the surface finish of the casting, so as to produce high-quality die castings.
