Pretreatment Of PVD Coating Process – Polishing

- Apr 03, 2018-

Polishing is to improve the surface finish of the workpiece or coating to reduce the resistance of the workpiece during use and reduce friction. The finish that polishing can achieve is much higher than the sandblasting process. The best surface roughness that can be achieved by sandblasting is Ra1.0, and the polishing can be as far as Ra1.0 or less up to the mirror surface, and the polishing is divided into pre-coating polishing and post-coating polishing. The polishing process is mainly applied to the coating of the mold.

1. Processing principle and characteristics

With a high-speed polishing wheel coated with abrasive paste (more diamond paste), and finishing the surface of the workpiece. Polishing wheels are generally made of felt, rubber, leather, cloth, etc. The method is simple, economical and easy to process, but it can only reduce roughness and the working conditions are poor. It is mainly used for the decorative polishing of parts, friction and wear parts and various kinds of molds and standard parts.

2. Application of polishing and passivation on the hob coating

Hob is a very important tool, and it is the main tool for machining gears. With the development of modern processing gear technology, the requirements for hobs are also increasing. High speed and hard tooth surface processing is very popular, so most of the hob must be PVD coated.

After the use of TIN coated hob, under normal circumstances, the hob should be regrind and decoating, and then coated. But after regrinding, it is estimated that there will be defects such as roll rim, burrs and gaps. If these defects are not eliminated, the quality of the coating will be directly affected. For example, if there is a burr, the coating will be attached directly to the burr. During the operation of the hob, the burr will soon fall off, and the coating will fall off, and the wear will naturally accelerate.

Many engineering and technical personnel believe that using a very fine-grained grinding wheel will not cause defects, which is a misunderstanding. The hob does not passivation and polishes the direct coating, and the coating is easily detached when attached to the curl edge. If the hob is passivated and polished, and then coated, the surface of the coating is smooth and has strong adhesion.