Polishing, also known as repair, is an important part of metal surface processing. Because the metal will produce high temperature in the process of processing, the material becomes softer, sticky and poor fluidity. It is easy to stick to the mold and produce various surface defects (fold, burr, crack, etc.). Before the next process, it must be grinded, repaired and clean, otherwise the defects will be further expanded in the subsequent process. It even causes the product to be scrapped.
        Repair tools include abrasive belts, nylon wheels, polishing wheels, etc. The defect should be corroded before the repair. The wound should be smooth and the width should be 5~10 times the depth.