Injection molding machine screw head three small parts

1、 The overall surface of the three small parts of the screw head should be smooth, and there should be no right angle, sharp angle, or dead angle visible from the front, except for the assembly part. They should be transitioned smoothly. The size of the smooth R depends on the situation, as sharp corners at right angles can easily crack and accumulate material, causing insufficient flow of raw materials. This can lead to black spots and yellowing during a long period of time. Remember that the three small parts are the most prone to yellowing, and many yellowing phenomena such as PC and PMMA only begin to turn yellow in the three small parts.
2、 The design of the two end faces passing through the rubber ring is also particularly important. Nowadays, many injection molding machine manufacturers design the joint surface between the rubber ring and the meson to be flat without inclination. This has two drawbacks:
1. Flat contact is not as large as inclined contact, so the service life is much shorter than inclined contact
2. The interface between the meson and the screw head becomes a dead corner, and if the raw material stays for a long time, there will be black spots and yellowing. It is best to have a slope of 30 degrees. If it is not high enough at 15 degrees, it is easy to accumulate material. If the contact surface is large at 45 degrees, it is not easy to accumulate material, but it is easy to support the rubber ring during injection.
3、 The clearance between the left and right sides of the rubber ring should be moderate, depending on the selection of production materials or the size of the clearance. Many large machine thin-walled products have unstable injection points due to the large left and right movement gaps passing through the rubber ring. There are also many PMMA and PC raw materials that make creaking noises during production due to the small gap between the left and right movement of the rubber ring, which leads to unsmooth discharge.
4、 The surface of the threaded part of the screw head does not need to be as hard as other parts, as high hardness can easily cause the thread to bounce off and decrease its strength. It should be protected by nitrogen before heat treatment or the thread should be machined after nitriding. It is best to use an R in the arc as the cutting groove of the thread, rather than cutting it directly with a right angle turning tool. That way, the stress is better, and many screw heads break at this location.