It is not easy to finish a set of high precision mould of mirror polishing. During polishing, the issues of smoothness of the mould may occur. There are some phenomenas such as graining, orange peel, ripples and bank marks on the mould surface.
Today, let's talk about bank marks.

Usually, there are two main reasons causing bank marks when mirror polishing the moulds.

1. It is due to the uneven metal structure of the mould steel.
2. It is the too long time polishing machine time, or too high tool speed when polishing that causes the steel surface heating, and then it leads to the microscopic structure change. Thereby, the problem of bank marks appears in the mould surface.

So how to solve the issue of bank marks?

Generally, it is necessary to re-polish this kind of mould steel, to re-grind the rough surface into smooth one, and then to use sandpaper and diamond abrasive paste to grind the surface until it is smooth.