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Design of screw head and rubber ring of screw-to-injection molding machine

Update:20 Mar 2020
Summary:

The three small parts of the screw head of the injectio […]

The three small parts of the screw head of the injection molding machine play a role in sealing, mixing, plasticizing and other functions in the entire screw group. It is a relatively important part. The quality of many plastic products of the injection molding machine is closely related to the three small parts of the screw head of the injection molding machine. Relationship, often there are many details of the three small pieces that have not been handled properly, so that the waste rate of plastic products has increased significantly, and even forced to shut down for maintenance. Now I point out the following points in the hope of bringing convenience to plastic friends.

1. The overall surface of the three small parts of the screw head of the injection molding machine must be smooth. There must be no right angle, acute angle, and dead angle in any place that can be seen from the front except the assembly part. All should be smooth transition. The size of the smooth R depends on the situation, because Right angle acute angle dead angle is easy to crack, not to mention easy to accumulate, so that the flow of raw materials is not smooth, and black spots are prone to yellowing over time. Remember that three small pieces are the most prone to yellowing, and many do PC.PMMA and other yellowing phenomena. It only started to turn yellow in three small pieces.

2. The design of the two end faces of the rubber ring is also very important. Now the joint surface of the rubber ring and the meson designed by many injection molding machine manufacturers is flat without slope, so there are two disadvantages. First, there is no shoe upper in contact with the plane. The contact surface is large, so the service life is much shorter than that of the inclined surface. Second, the junction of the meson without the inclined surface and the screw head of the injection molding machine becomes a dead angle. If the raw material stays for a long time, there will be black spots and yellowing. This slope is preferably 30 degrees, 15 points is not large enough to accumulate material, 45 degrees contact surface is large, it is not easy to accumulate materials, but it is easy to burst the rubber ring when shooting.

3. The gap between the left and right movements of the aprons should be moderate, depending on the choice of raw materials for production, whether large or small, and the gap between many large machines for thin-walled products is not stable because the left and right movement gaps of the aprons are too large. There are also many PMMA and PC raw materials that make a rattling sound during production because the gap between the left and right sides of the rubber ring is too small, resulting in unsmooth discharge.

4. The surface of the screw part of the screw head of the injection molding machine does not need to be as hard as other parts. If the hardness is too high, the thread will jump off and the thread strength will decrease. It should be protected by nitrogen before heat treatment or the thread should be processed after nitriding. The sipe is preferably an R of an arc, instead of being cut directly by a right-angle turning tool. That stress is a bit better, and many injection molding machine screw head fractures are in this part.