PMMA plastic injection molding process

In recent years, as people's living standards have increased, cars have entered homes, the demand for plastics has increased, the popularity of VCDs, the advent of DVDs, and the demand for transparent plastics have become greater. As a transparent plastic, PMMA has a high light transmittance. Widely used in high-precision telescope lenses, eyepieces, objectives, but the injection molding process has been difficult to break through, and the technology has been monopolized by Japan, although domestic companies and research institutes have research but still can not break through, this has always been the pain of the people, I hope you all have been See, publish some of your own opinions, especially the precision injection molding process.

PMMA injection molding is indeed very troublesome, there are many experiences, there are many mold factory in the connection of this mold are considered very simple, on a piece of thin, the mold is finished is not easy to find! I design and manufacture many models of SONY DVD lenses, Daewoo car audio panels, buttons, etc., optical lenses I have repaired this type of mold, mold is actually not difficult, the key is to use CNC optical polishing machine polishing, to make this type of mold, From the beginning of design to production, we must pay attention to:

1. According to the size and thickness of the product, and the amount of glue injected by the plastic machine, the number of cavity points is determined. Generally, two holes or four holes are opened. There is no benefit from too much, and the buttons can be opened a little more.

2. It is very important to do mold flow analysis first when designing, especially for some rectangular lenses, the best point is to enter the glue point at the corner of the long side by 15mm, if the product here happens to have one touch perforation, or minus glue. The bit is even better. It is easy to adjust the pattern and glue marks during production.

3. The design of the exhaust position, the general transparent lens is not allowed to have the needle marks, should open the auxiliary flow channel to help the top out, this flow channel will play the role of exhaust, generally adhere to a principle, there are corners where there must be excessive exhaust.

4. The design of the flow channel and the plastic inlet, the flow channel is trapezoidal, the plastic inlet is open and the flow channel is polished to be very bright.

5. The choice of steel, the general output of less than 100,000, the Japanese can be produced NAK80 on it, if the output is large, you must use S136 or French SMV3W high-mirror heat-treated steel, heat treatment to HRC52, and then after finishing Polishing, the effect is very good, PMMA itself has a certain degree of corrosivity, the use of heat-treated steel can completely eliminate the mold surface after a period of time the phenomenon of pitting, of course, steel must be purchased in the original factory, and now many domestic or completely counterfeit S136, completely failed to achieve this effect, if the map is cheap, buy this material, everything is done, is the surface thrown off, how to throw are dark steel texture, regret it too late, S136 directly in One wins 100 or Long Kee company to buy, they are responsible for heat treatment, SMV3W only Long Kee agent, the use of the same effect as S136.

6. The mold should be filled with oil at the time of injection, and the temperature should be kept at 120 degrees. A mold special temperature meter should be installed on the mold when the mold is manufactured.

7. The plastic machine table should use small screw of type A, or PC smaller than screw of type A, special screw of PMMA, high firing speed. This is the basic guarantee of good or bad quality of molding, and there is a kind of precision injection of the whole motor. Machine, the molding effect is very good, and now all the plastic machine manufacturers have developed this special machine.

8. There are some very thin transparent parts that can be injected with nitrogen and high pressure. This is a special machine. Now there are some injection molding methods. The first injection and then high pressure molding