Do not use the finest whetstone, sandpaper, or abrasive polishing paste at the beginning of mold polishing, as you can't throw away the rough lines. The living surface polished in that way looks very shiny, but when you take a side view, the rough lines appear. Therefore, it is necessary to polish from coarse whetstone, sandpaper or abrasive polishing paste, then change to finer whetstone, sandpaper or abrasive polishing paste for polishing, and finally polish with the finest abrasive polishing paste. This seems to be cumbersome and there are many processes. In fact, it is not slow. One process after another, the rough processing lines in the front are polished off, and then the following injection molding process step is carried out without rework, and the injection molding surface finish can meet the requirements with one step.