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Understanding injection molding and mold flow simulation

In most cases injection mold shop will end up making "acceptable" parts by "shrink fixing" it. There goes all profit and residual stress is introduced.

I am asking Chinese mold flow experts- have you produced mold flow simulations with tools where either part thickness varies and or cooling channels are not uniform, or are not conformal with uniform pitch- how do you model uneven tool temperatures and uneven part thickness average temperature? Would you deliver a mold flow simulation with differential mold shrinkage so tool can be cut with compensation? Otherwise we are back to surrogate tool or prototype too?
On prototype mold worth remembering the tool material and cooling geometry can have vast difference in shrinkage and be disaster when proceeding to production tool from Al tool with minimal cooling.

The modeling and feedback over a few years can help you in hitting that elusive injection molding first home run. But the mold flow expert has to have material and hands on knowledge of injection molding to do what you are suggesting.

I took two gifted folks off the molding floor one turned into a great tool engineer and the other one into one of the best mold flow guys I ever saw. (Fortunately I started playing with mold flow in the early 80's so come by my training and skill honestly today). Their skill in deleting issues with the simulation and correcting not only the software clutches but also used their experience to guide themselves in making good countermeasures to solve many tooling/process/part design issues. Accurate modeling of the "real" mold and final tool part design and manipulating the set up data to understand the limits of the process guided them directionally away from differential shrink towards over-packing issues for example and vise versa. Identifying sheer and temperature issues also requires a bit of sleuthing as venting and gas traps can kill you plus the basics of machine errors due to poor check ring maintenance where the set up appears ok yet packing/shrink is NG because the check ring leaks. Mold flow will not tell you that a check ring is bad but mold flow will tell you - you are in the ballpark on set up (assumptions your machine is ok otherwise) and one needs to start checking other items as root cause.

So one can model a poor injection mold and directionally tell you where to compensate with well-trained folks. And it takes time to compensate accurately the necessary tooling geometry changes to predict the optimum solution - change the gating or sculpture some thickness somewhere. Mold flow directionally can help but experience with measurements and understanding tools and injection molding all in one is the holy grail.

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