Since mechanical polishing is mainly completed manually, polishing technology is still the main reason affecting the quality of polishing.In addition, it is also related to mold material, surface condition before polishing, heat treatment process and so on. High quality steel is the prerequisite to obtain good polishing quality, if the surface hardness of steel is uneven or there are differences in characteristics, often will produce polishing difficulties. Various inclusions and pores in steel are not conducive to polishing. Below are the two factors which affect the quality of die polishing:     

1). Effect of different hardness on polishing process: Increasing hardness makes grinding more difficult, but the roughness decreases after polishing. As hardness increases, the polishing time required to achieve lower roughness increases correspondingly. At the same time, the hardness increases, the possibility of excessive polishing is reduced.                     2). Influence of workpiece surface condition on polishing process: Steel in the cutting process of mechanical processing of the crushing process, the surface will be damaged by heat, internal stress or other factors, improper cutting parameters will affect the polishing effect. The surface after edm is more difficult to grind than the surface after normal machining or heat treatment. Therefore, precise standard edm dressing should be adopted before the end of edm, otherwise the surface will form a hardened thin layer.If the edm finishing specification is not properly selected, the depth of the thermal impact layer can reach a maximum of 0.4mm. The hardness of the hardened thin layer is higher than that of the matrix and must be removed. Therefore, it is best to add a rough grinding processing, thoroughly remove damage to the surface layer, constitute an average rough metal surface, polishing processing provides a good foundation.