An Integrated Approach to Evaluate the Cycle Time in Injection Molding

Abstract

The cycle time prediction is considered as a critical issue in injection molding. It relates directly to the production rate and the part quality. It is commonly defined as the time duration between the start of the injection and the ejection of the part. When the cycle time exceeds the desired range, the production rate will be compromised. In some cases, due to excessively increased friction force, the part may be subject to severe failure such as breakage during ejection. Another possible situation is that the ejector pins can be damaged because the friction force exceeds the maximum ejection force that the machine can provide through the ejectors. If the part is ejected too early, only a thin layer of polymer is solidified and the ejection may cause the part to be deformed permanently which generally leads to surface defects. For most injection molders, the cycle time is estimated through molding trials, which is very costly and time consuming. In the case of testing a new material, it is even more difficult to determine a proper cycle time ranger due to the lack of knowledge on the material behavior.