Essentially, you cannot generate reliable machine independent process documentation based on process outputs if the mold cavity fills completely during 1st stage injection.
Problem: I see many companies trying to utilize machine-independent process documentation while still filling the cavity completely during 1st stage injection. Since the mold cavity is both filled and packed during first stage injection it can only be repeated when the material has the identical viscosity at the time the process was documented. Each time the material viscosity changes, the amount of filling and packing during first stage injection will change, requiring adjustments to the overall process. For this reason, machine-independent process documentation is only a moderately helpful tool when the cavity is 100% full at the time of transfer.
Resolution: Fill the mold 90 to 95% full during first stage injection and then pack out the part using 2nd stage packing pressure. This will allow you the benefit of documenting important repeatable process outputs such as 1st Stage Time, Melt Temperature, and 1st Stage Short Shot Weight.
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