Plastic Tool, Mold Manufacturing and Plastic Injection Molding

Problem:

Customer had a cover mold with internal threads built with an unscrewing device. They approached us and said they were having the following difficulties with the mold:

1. Unscrewing device was not working consistently; parts often got stuck during unscrewing, thus production was delayed by 2 hours every time this happened.
2. Cycle time is taking too long because unscrewing molds need to unscrew the part out before the part can be ejected from the mold.
3. Production output is low.
4. Scrap rate is high.

Process/Solution:

Richfields team looked into the 3D model of the part, and analyzed the functions of the plastic part produced by this mold. We noticed that the threads are not deep enough and can actually be ejected by forced ejection using an ejector plate. This will make it simpler instead of using an unscrewing device. These are the things that we did:

1. Re-built the tool using an ejector plate only, without using an unscrewing device. The ejection process was a Forced ejection. We added some drafts on the threads facing the ejection direction so that the threads will not be damaged during forced ejection.
2. Proper tool layout to achieve efficiency during production.
3. Injection Molding Parameters were set to achieve best parts.

Very simple changes actually resolved the problems mentioned before by the customer. Richfields was able to achieve the following for the customer:

1. No more troubling with unscrewing device since we are doing forced ejection using ejector plate.
2. The cycle time per shot cycle is 8 seconds faster than the original mold design using unscrewing device.
3. Production rate is now very consistent and has high production yield.
4. Scrap rate minimal.