In the plastic mold processing said polishing and other industries in the surface polishing is very different, strictly speaking, the mold polishing should be called mirror processing. It not only has a high demand for polishing itself but also has a high standard for surface flatness, smoothness and geometric accuracy. Injection mold Surface polishing generally requires only to obtain a bright surface.
The standard for mirror processing is divided into four levels:
AO = Ra0.008μm, A1 = Ra0.016μm, A3 = Ra0.032μm, A4 = Ra0.063μm, due to electrolytic polishing, fluid polishing and other methods is difficult to accurately control the geometric accuracy of parts, and chemical polishing, ultrasonic polishing, magnetic Grinding and polishing methods such as the surface quality and fail to meet the requirements, so the precision mold mirror processing or to the main polished.
(A) manual polishing of the basic procedures
In order to obtain high-quality polishing effect, the most important thing is to have high-quality Whetstone, sandpaper and diamond polishing paste and other polishing tools and accessories. The most important is the polishing of the working environment, Injection mold the requirements are clean workshop. The choice of polishing process depends on the pre-processed surface conditions, such as machining, EDM, grinding and so on.
The general process of manual polishing is as follows:
(1) hand-oil mill grinding, strip of lime plus kerosene as a lubricant or coolant. The general use order is # 180 ~ # 240 ~ # 320 ~ # 400 ~ # 600 ~ # 800 ~ # 1000. Many mold manufacturers have chosen to start from # 400 in order to save time.
(2) semi-fine semi-fine cast mainly use sandpaper and kerosene. The number of sandpaper is: # 400 ~ # 600 ~ # 800 ~ # 1000 ~ # 1200 ~ # 1500. In fact # 1500 sandpaper only for hardened die steel (52HRC above), and not for pre-hardened steel, because it may lead to pre-hardened steel surface burns. In the case of
(3) fine polishing the main use of diamond grinding paste. The grinding order is usually 9 μm (# 1800) to 6 μm (# 3000) to 3 μm (# 8000) if the polishing is carried out using a polishing cloth wheel mixed with a diamond grinding or grinding paste. 9μm diamond grinding paste and polishing cloth wheel can be used to remove the # 1200 and # 1500 sandpaper left hair wear marks. (# 14000) to 1 / 2μm (# 60000) to 1 / 4μm (# 100000), Injection mold followed by polishing with a clay and a diamond abrasive paste. In the case of
Accuracy requirements in more than 1μm (including 1μm) polishing process in the mold processing workshop in a clean polishing room can be carried out. If you want to carry out more sophisticated polishing must be an absolutely clean space. Dust, smoke, dandruff and mouth foams are likely to be scrapped for several hours after work to get the high precision polished surface.
(B) manual polishing to pay attention to the problem
Polishing with sandpaper should note the following:
(1) polishing with sandpaper requires the use of soft sticks or bamboo sticks. In the polished round or spherical, the use of cork can be better with the round and spherical curvature. While harder wood like cherry wood is more suitable for flat surface polishing. The end of the trimmed wood is such that it can be aligned with the surface shape of the steel, thus avoiding the sharp scratches on the surface of the steel piece at the acute angle of the wood (or bamboo).
(2) When changing the different types of sandpaper, the polishing direction should be converted to 45 ° ~ 90 °, before the kind of sandpaper after polishing a strip of shadows can be distinguished.
Before grinding different types of sandpaper, Injection mold the polished surface must be carefully wiped with 100% pure cotton dipped in alcohol or the like, because a small gravel left on the surface to destroy the entire polishing work. This cleaning process is equally important when polishing from abrasive paper and diamonds. All particles and kerosene must be completely clean before polishing continues. In the case of
(3) In order to avoid scratching and burning the surface of the workpiece, special care must be taken when polishing with # 1200 and # 1500 sandpaper. It is therefore necessary to load a light load and polish the surface with a two-step polishing method. With each type of sandpaper for polishing should be carried out in two different directions twice, between the two directions between the rotation 45 ° ~ 90 °.
(C) diamond grinding and polishing should note the following:
(1) This polishing must be carried out as much as possible under less pressure, especially when polishing the pre-hardened steel and polishing with a fine grinding paste. In the # 8000 grinding paste polishing, the common load of 100 ~ 200g / cm2, but to maintain the accuracy of this load is difficult to do.
In order to do this easier, you can make a thin and narrow handle on the wood, such as adding a copper piece; or cut a part on the bamboo to make it more soft. This can help control the polishing pressure to ensure that the mold surface pressure is not too high.
(2) When using diamond grinding and polishing, not only the work surface requires clean, the worker's hands must also be carefully cleaned. In the case of
(3) each polishing time should not be too long, the shorter the time, the better the effect. If the polishing process is too long will cause "orange peel" and "pitting".
(4) In order to obtain high-quality polishing effect, Injection mold easy to heat the polishing methods and tools should be avoided. For example: polishing wheel polishing, polishing the heat generated by the wheel will easily lead to "orange peel."
(5) When the polishing process is stopped, it is important to ensure that the surface of the workpiece is clean and carefully removed from all abrasives and lubricants, Injection mold and then a layer of mold rust coating should be sprayed on the surface.