Some common problems in daily polishing and their corresponding solutions.

The biggest problem encountered in the daily polishing process is “over-polishing”, which means that the longer the polishing time, the worse the quality of the mold surface. There are two phenomena of excessive polishing: “orange peel” and “pitting”. Over-polishing often occurs in mechanical polishing.

1)Causes of “orange peel” on workpieces

Irregular and rough surfaces are called “orange peel”. There are many reasons for “orange peel”. The most common reasons are due to overheating of the mold surface or excessive carburization. Excessive polishing pressure and too long polishing time are the causes. The main cause of “orange peel.”

2)Measures to eliminate “orange peel” on workpieces

1.Remove the defective surface, grind with a slightly coarser grain size than the previously used sand, and then grind with a lower polishing intensity than before.

2.Stress relief is performed at a temperature 25°C lower than the tempering temperature. Use the finest sand grade for grinding before polishing until a satisfactory effect is achieved, and finally polish with a lighter intensity.

3)Causes of “pitting corrosion” on the workpiece surface

Because there are some non-metallic impurities in steel, usually hard and brittle oxides, they are pulled out from the steel surface during the polishing process, forming micro-pits or pitting corrosion. The main factors that produce “pitting corrosion” are as follows:

1.The polishing pressure is too high and the polishing time is too long.

2.The purity of the steel is not enough and the content of hard impurities is high.

3. The mold surface is rusty.

4. The black leather has not been removed.

4)Measures to eliminate pitting corrosion of workpieces

1.Carefully re-grind the surface to a slightly coarser grit than previously used. Use a soft and sharpened whetstone for the final grinding step before polishing.

2.The softest polishing tools should be avoided when the grit size is less than 1 mm.

3.Use the shortest polishing time and minimum polishing intensity possible.