Injection moulding Gurus – can you solve this moulding quandary?
Cyclic Cushion variation every 35 or 40 shots.I have noticed the following phenomenon which I cannot explain. I am running a job which exhibits an incremental change in cushion each cycle for about 20 shots and then begins to decrease and return to nominal. This is then repeated..every 35 to 40 shots. Moulding is in a 100 Ton JSW EIII hydraulic machine.
My first suspicion was that it may be resulting from the regrind from the sprue, however the same result occurs with 100% virgin materials.
I’d be interested in hearing from anyone who has a theory.
As part of the investigation process, I would also verify the following to see if they are varying over time: hold pressure, shot size, hydraulic oil temperature(could affect pressures and speeds), temperatures in the injection barrel and hot runner, if applicable, and cooling water to the feed throat.
There are of course many interacting variables in the molding process, several of which could cause this phenomenon.
Once you complete your investigation, I would be interested in knowing what you find.
Also...re: cushion control.. I don't know anyone that has ever used it, don't recommend it, and don't understand why its even an option....