Short Shot / Insufficient Filling

The end of the part is not fully filled, and material shortage appears. When a short shot occurs, obvious material shortage appears at the end of the part far from the gate or in thin-wall areas, with incomplete edges showing serrated or arc-shaped defects. This defect usually occurs in part structures with a large flow-length ratio and thin wall thickness, and is more likely to appear under high-speed filling or low-temperature conditions. Short shot directly causes the part to become scrap; the material-shortage area cannot bear the service load, and at the same time the mold cavity accelerates local wear because it cannot obtain melt pressure support.

1. Process parameter factors: insufficient injection pressure, low melt temperature, too slow injection speed, poor mold venting, runner/gate too small.

1. Process parameter optimization and adjustment: increase injection pressure and speed, raise barrel temperature, enlarge gate size, improve mold venting. 2. Systematic troubleshooting method: troubleshoot item by item in the order of "parameters -> material -> mold -> equipment". First adjust the parameters that are easiest to change, such as injection pressure and temperature, and observe the effect; if there is no improvement, check the drying and fluidity of the raw material; further check mold venting and gate design; finally check the mechanical condition of the equipment (check ring, screw). Change only one variable at a time to determine the root cause. 3. Preventive management: establish standardized process parameter cards and quality control limits for each mold/product, and regularly conduct process capability index (CPK) evaluation. For recurring problems, use fishbone diagram or 5Why analysis to trace the root cause, and fix the countermeasures as PFMEA control points.

The essence of short shot is that the melt flow ability is insufficient to overcome the cavity filling resistance. The core solution idea is "exerting force in both directions": reducing flow resistance (optimizing mold venting and gate design) and enhancing flow drive (increasing injection pressure and melt temperature); the two need to be adjusted coordinately to fundamentally eliminate the defect.