Plastic Injection Mold Surface Treatment

- Dec 27, 2018-

With the wide application of plastic products, the appearance quality requirements of plastic products are getting higher and higher, and the surface polishing quality of injection mold processing is also correspondingly improved, especially the mold surface roughness of the mirror surface and high gloss high surface. The requirements are higher and therefore the requirements for polishing are higher. Polishing not only increases the aesthetics of the workpiece, but also improves the corrosion resistance and wear resistance of the surface of the material. It can also facilitate the subsequent injection molding process, such as making the plastic product easy to demould and reducing the production cycle.

Commonly used polishing methods are as follows:

1: Mechanical polishing of injection mold processing

Mechanical polishing is a polishing method that removes the polished convex portion by plastic deformation on the surface of the material to obtain a smooth surface. Generally, oil stone strips, wool wheels, sandpaper, etc. are used, which are mainly manual operations, and special parts such as the surface of the rotating body can be used. Using an auxiliary tool such as a turntable, the method of super-fine polishing can be used with high surface quality requirements. Ultra-fine grinding and polishing is a special-purpose grinding tool. In the polishing liquid containing abrasive, it is pressed against the machined surface to perform high-speed rotary motion. With this technology, a surface roughness of Ra0.008 μm can be achieved, which is the highest among various polishing methods. This method is often used in optical lens molds.

2: Chemical polishing of injection mold processing

Chemical Polishing Chemical polishing is a process in which a portion of a material that is microscopically convex in a chemical medium is preferentially dissolved in a concave portion to obtain a smooth surface. The main advantage of this method is that it can polish a workpiece with complex shapes without complicated equipment, and can polish many workpieces at the same time with high efficiency. The core issue of chemical polishing is the formulation of the polishing fluid. The surface roughness obtained by chemical polishing is generally several 10 μm.

3: Electropolishing of injection mold processing

Electropolishing The basic principle of electropolishing is the same as chemical polishing, which is to selectively dissolve the surface of the material to make the surface smooth. Compared with chemical polishing, the effect of the cathode reaction can be eliminated, and the effect is better.

4: Ultrasonic polishing of injection mold processing

Ultrasonic polishing The workpiece is placed in an abrasive suspension and placed together in an ultrasonic field. The abrasive is ground and polished on the surface of the workpiece by the action of ultrasonic waves. Ultrasonic machining has a small macroscopic force and does not cause deformation of the workpiece, but it is difficult to manufacture and install the tooling. Ultrasonic processing can be combined with chemical or electrochemical methods. On the basis of solution corrosion and electrolysis, ultrasonic vibration is applied to stir the solution to dissociate the dissolved products on the surface of the workpiece, and the corrosion or electrolyte near the surface is uniform. The cavitation of the ultrasonic wave in the liquid can also inhibit the corrosion process and facilitate surface illuminating.

The polishing described in the injection mold processing is very different from the surface polishing required in other industries. Strictly speaking, the polishing of the mold should be called mirror processing. Not only does it have high requirements for polishing itself, but it also has a high standard for surface flatness, smoothness and geometric accuracy. Surface polishing generally requires only a shiny surface. The mirror processing of precision molds is mainly based on mechanical polishing.

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