Reasons and solutions for excessive polishing

Reasons and solutions for excessive polishing
Mold polishing is the process of using polishing tools to cause plastic deformation on the surface of a material, thereby removing protruding parts from the workpiece surface and obtaining a smooth surface. The tools used for polishing are generally oilstone strips, wool wheels, sandpaper, etc., and the operation method is usually manual. For some workpieces with high surface quality requirements, special grinding tools can be used for ultra precision polishing. Ultra precision polishing is the process of compressing a special grinding tool onto the machined surface of a workpiece in a polishing fluid containing abrasive, and performing high-speed rotational motion. The surface roughness produced by this grinding can reach 0.008 μ M.
During the polishing process, there may be an issue of excessive polishing, which occurs when the polishing time is too long and leads to a deterioration of the surface quality of the grinding tool, often occurring in mechanical polishing. Specifically, there are two different manifestations of excessive polishing, namely "orange peel" and "pitting". Let's take a look at the reasons for the two and how to eliminate them. The so-called "orange peel" refers to the surface roughness and irregularity of polished parts. The causes of "orange peel" include excessive polishing pressure, long polishing time, overheating of the mold surface, and excessive carburization of the workpiece. For example, if a Polishing Buff Wheel is used for polishing, once the polishing time is not properly controlled, the heat generated by the Polishing wheel can easily cause "orange peel" on the surface of the workpiece.

The difficulty of producing "orange peel" varies among different types of materials. Materials with higher hardness can withstand greater polishing pressure and are less likely to produce "orange peel"; However, workpieces with lower hardness are more prone to excessive polishing, resulting in orange peel. Measures to eliminate "orange peel"

In practical operation, there are some erroneous practices, and many people choose to improve surface quality by increasing polishing pressure and extending polishing time when they find poor surface quality. In fact, sometimes this approach not only does not improve surface quality, but also has the opposite effect.
The correct method to remove "orange peel" should be to first remove the defective surface, and then use a Wire Drawing Wheels with a slightly coarser particle size than the previous sand to polish with a smaller polishing force. Alternatively, stress relief can be applied to the workpiece at a temperature 25 degrees Celsius below the tempering temperature, followed by grinding with the finest Cotton Cloth Wheel until satisfactory results are achieved, and finally polishing with a lighter force. The causes of "pitting corrosion"
The so-called "pitting" refers to the occurrence of pitting on the surface of the polished workpiece. This is because there are some non-metallic impurities mixed in the metal workpiece, usually hard and brittle oxides. If the polishing pressure is too high or the polishing time is too long, these impurities will be pulled out of the steel surface, forming point like micro pits. Especially when the purity of steel is insufficient and the content of hard impurities is high; Just now, if the surface is rusted or the black leather material has not been cleared of emotions, it is more prone to pitting corrosion.
Measures to eliminate pitting corrosion

Firstly, re grind the surface of the workpiece, using a grinding tool with a slightly coarser particle size than the previously used one, and the grinding force must be small. Then use soft and Gude Polishing Compound for the final step of grinding, and after achieving satisfactory results, proceed with the polishing procedure. When polishing, if the size of the sand particles is less than 1 millimeter, the softest polishing tool should be avoided. The intensity of running light should be as small as possible, and the time should be as short as possible.