The general process of polishing is to polish the mold surface with a fine file first, then polish the filed place with a coarse oilstone, and grind off the filed lines, then grind off the lines ground with a fine oilstone, and then polish the ground with a fine metallographic sandpaper. This is the whole process of mould polishing technology in previous years. Now there is an ultrasonic polishing machine, which uses polishing paste and grinding paste. Some processes that were originally to be polished by hand have been processed by polishing machines. Efficiency has also improved a lot, and fluency has also improved a lot.