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Why is the cooling time THAT long?

(A) "Why is the cooling time THAT long"
Because that is what the shrink rate built into the injection mold will allow for dimensionally acceptable parts. I have optimized gate seal, cooling rate, fill rate and melt temp. Unfortunately the injection mold maker missed the shrink on the steel.

(B) "in plain language how do you duplicate the process in machine "A" when you put that mold in machine "B" that has a different size/capacity injection unit and clamp and not start from scratch?"

NO I duplicate the plastic conditions from machine A to machine B, Melt temp, Flow rate, pack/hold pressure (calculated by knowing the difference in Ri) and cooling rate (calculated using Reynolds # and coolant temp)

(C) even better "How do you know that waterline hookup is (1) optimal for that mold and (2) identical to the last five times you ran it?"

Reynolds calculation and/or delta P as for pattern I consult the water line diagram.

(D) And, the ultimate ship sinker "what is the ONE cause of short shots"

There is no ONE root cause for short shots. Material viscosity changes from lot to lot. A properly optimized process will adapt to those viscosity shifts however if one of the four plastics variables change you can produce a defect. For instance if I am running Polycarbonate and the thermolater kicks off the machine will try to fill the part but may not have enough pressure available to complete the fill..... shorts.... Parting line vents can become clogged gas cannot escape...burns and or shorts depending on the geometry and other factors.
An orifice (gate or nozzle tip) is partially obstructed machine tried to fill but clock timed out or pressure limited....Shorts.
Melt Temp has changed due to a bad heater band or someone changed the screw RPM etc. etc.

Now one could say the ONE cause for short shots is "You didn't get enough material in the cavity" and this would be correct however it is a symptom NOT a root cause. The root cause is that at least one of the four variables has changed. Determine which one/ones and you are on the path to a solution.

(or any other of the 18 routine molded part defects) that explains every solution you're going to try to correct this defect?"

Every defect cannot be lumped into a simple one answer solution. if one of the plastic variables change the part will change. It is all about control... :If you are not controlling the process...the process is controlling you." Hence the common statement I hear all the time from students. "I don't have time to optimize the process. I am too busy putting out fires" I always tell them... this is the process controlling YOU, because you are not controlling it.

Teach a technician to make data driven decisions based on actual plastic conditions and you have produced an effective technician on his way up the ladder in the industry.

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