Record the fill time and machine peak hydraulic pressure for 3 shots.Ģ1. Add adequate hold time and pressure, so no sink marks appear and parts eject.ġ9. If you do not adjust the feed stroke, you risk having bogus results.ġ8. Adjust feed stroke to maintain approximately 90% part weight with lower fill rate. If the machine is equipped, set pack time and pressure to zero.ġ7. Note: When you decrease the fill rate the parts will become less filled.ġ6. Record the fill time and machine peak hydraulic pressure for 3 shots. Note: It is not important to be molding good parts to complete this study.ġ2. Add adequate hold time and pressure, as well as pack time and pressure, so no sink marks appear and parts eject. Have sufficient cushion to prevent the screw from bottoming out against the barrel during injection.ġ1. Note: Use full part weight established during process stability test to calculate 90%.ġ0. Adjust feed stroke so that the most filled part is approximately 90% filled by weight. Transfer from injection to hold phase by screw position.ĩ. Set fill rate as fast as possible without flashing, burning or damaging the mold.Ĩ. Set cooling time long enough so that parts eject consistently without being distorted.ħ. If the machine is equipped, set pack time and pressure to zero.ĥ. Measure and record the melt temperature.ĥ. Set mold temperature to resin manufacturer's recommended mid-range.ģ. Set melt temperature to resin manufacturer's recommended mid-range.Ģ. Part may stick in mold and need to be removed manually.ġ. These results, when interpreted properly, can be used to identify the proper fill time.Īll the steps during the procedure that involve intimate contact with the injection molding machine are to be done by a qualified injection molding machine operator.Ĭaution: Part geometry dependent. A fill time analysis should have been performed to determine the proper injection time for the mold. The mold viscosity test could be skipped if mold fill analysis has been performed on the mold. The injection rate should be recorded in volume per unit time so that the learnings and results of the mold viscosity test can be transferred to another press that may have a different size injection unit. The mold viscosity test should be performed on the correct size press, for which the mold was designed. The theory behind using high speed injection rates is to take advantage of the decreased viscosity which results when plastics are subjected to high shear rates.
The mold viscosity test was developed to identify the maximum and minimum fill rates permissible for the mold with a specific plastics material. Gage repeatability & reproducibility (R&R) test The fifth step in validating a injection mold with the overall process shown in figure injection mold validation flow chart is mold viscosity test.
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