Simulating wall friction

[extrmDovahkiin]

The idea is to find out the minimum number of ejector pins required for a de-molding process in an Injection Molding scenario. I don't really want to simulate Injection molding simulation per se, as I think only the de-molding part concerns me at the moment. With some search online and through some research papers, I found a formula that approximates the ejection force required for a separation of a surface (here).

1. How can I model this ejection force in terms of surface Friction to mimic the ejection scenario (eg. to mimic a tendency to stick on sides that doesn't have pins around them) in Abaqus(or any software for that matter).

2. Since the top surface has varying geometry, how can I choose the top face nodes(highest Z for every X,Y) to loop through different pin location.

3. For the multi-objective optimization, I was planning to implement 2 objectives firstly -minimize strain energy, minimize pins. Is another realistic objective suggested?

Please point out if the posted question doesn't meet the forum's standards, or if it should belong to another forum.

Thank you

 

[FEA way]

In Abaqus (or other FEA software) you will have to define contact interaction between the plastic part and mold components. You will also have to specify friction coefficient for this interaction and it will be important to use accurate value as in this case results will significantly depend on the friction.

Keep in mind that various process parameters may influence the required ejection force so you might have to simulate the whole molding eventually. And these process parameters might be included in the optimization as well.

There are some scientific articles that discuss experimental and numerical evaluation of ejection force. For example check the one titled "Ejection forces and friction coefficients from injection molding experiments using rapid tooled inserts" by M.E. Kinsella et al.