Standards for mirror polishing of molds, methods and precautions for mold polishing
Release time:
2023-03-22
Polishing is a crucial process in the production of plastic molds. The process of polishing the surface of the mold cavity using oilstone, sandpaper, polishing paste, etc., to make the working surface of the mold bright as a mirror.
Mold polishing can make the surface of the produced product smooth and beautiful, and in addition, it can make the product easier to demould on the mold.
The standard for mold mirror polishing processing is divided into four levels:
A0=Ra0.008 μ m
A1=Ra0.016 μ m
A3=Ra0.032 μ m
A4=Ra0.063 μ m
1. Method of mold polishing
For mold polishing, do not use the finest oilstone, sandpaper, or polishing paste at the beginning. This will not remove the coarse lines. The polished surface will look bright, but when exposed to the side, the coarse lines will appear. Therefore, it is necessary to first polish with coarse oilstone, sandpaper, or polishing paste, then replace with finer oilstone, sandpaper, or polishing paste for polishing, and finally use the finest polishing paste for polishing.
This looks like it's quite complicated, with many processes. Actually, it's not slow. One process after another involves polishing off the rough machining patterns before proceeding with the next process, without rework. One step can achieve the required smoothness of the mold.
Generally, a coarse oilstone is used to roughly polish the surface of the machined mold cavity, removing the tool marks from the machining tool. Then, a fine oilstone is used to polish the rough oilstone to achieve the marks. Then, a fine sandpaper is used to polish the surface after the fine oilstone has been polished. Finally, a polishing paste or grinding paste is used to perform the final fine polishing and polishing on the surface of the mold cavity, achieving a shiny mirror like effect. This is the entire process of polishing the mold in general.
Of course, if possible, an ultrasonic polishing machine can be used to polish the mold, which is more efficient and labor-saving.
2. The following points should be noted when polishing with sandpaper
(1) Polishing with sandpaper requires the use of soft wooden or bamboo sticks. When polishing circular or spherical surfaces, using a cork stick can better match the curvature of the circular and spherical surfaces. Harder wood strips, such as cherry wood, are more suitable for polishing flat surfaces. Trim the end of the wooden strip so that it matches the surface shape of the steel piece, which can prevent the sharp corners of the wooden strip (or bamboo strip) from touching the surface of the steel piece and causing deeper scratches.
(2) When using different types of sandpaper, the polishing direction should be changed from 45 ° to 90 °, so that the stripe shadows left by the previous type of sandpaper after polishing can be distinguished. Before changing to different types of sandpaper, it is necessary to carefully wipe the polished surface with a cleaning solution such as 100% pure cotton dipped in alcohol, as leaving a small grit on the surface can damage the entire polishing process that follows. When switching from sandpaper polishing to diamond grinding paste polishing, this cleaning process is equally important. Before polishing can continue, all particles and kerosene must be completely cleaned.
(3) To avoid scratching and burning the surface of the workpiece, special care must be taken when polishing with # 1200 and # 1500 sandpaper. Therefore, it is necessary to load a light load and use a two-step polishing method to polish the surface. When polishing with each type of sandpaper, polishing should be carried out twice in two different directions, with each rotation of 45 ° -90 ° between the two directions.
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