7. Gate Freeze Test - Validation procedure for injection molds
The seventh step in validating a injection mold with the overall process shown in injection mold validation flow chart is Gate Freeze Test . The steps before: 1. Mold certification 2. Dry cycle mold 3. Process stability test 4. Gage repeatability & reproducibility (R&R) test 5. Mold viscosity test 6. Balance of fill analysis Purpose: The purpose of the gate freeze test is to identify the hold conditions necessary to freeze the gate. The extent and duration of hold pressure has a large effect on the dimensional stability and outer appearance of the molded part. If the hold time is too short, the gate will not have had enough time to freeze off and sink marks could appear on the part. This is especially true of larger parts and when higher hold pressures are employed. After the mold gates "freeze", hold pressure has no effect and should be terminated at that point. It is typically better to be a little high on the hold pressure timer setting. This will cause a sli...