A short shot is an incompletely filled molded part. It describes the observed defect, not its root cause. Flow restrictions, long or hesitant flow paths, trapped air, low melt or mold temperature, insufficient material delivery and machine problems can all contribute. The right corrective action depends on where and when the part stops filling.
Record the defect before changing settings
Identify the part number and drawing revision, resin and lot, machine and mold, cavity, affected location, production time and whether the defect appears at startup or during a stable run. Photograph the part against the agreed inspection criteria. Keep representative conforming and nonconforming samples when possible. Check whether the issue occurs in one cavity, several cavities or every cavity.
Use the pattern to guide the investigation
- One cavity or one local region: review that cavity’s flow path, gate condition, venting, cooling and tool condition.
- Several cavities or the same end-of-fill area: compare the runner balance, flow length, restrictions and venting against the mold layout and trial records.
- All cavities or intermittent shots: review material supply, shot delivery, machine records, check-valve condition and the stability of the approved process.
- A change after a material or color change: verify the actual grade, lot, preparation and approved material specification before attributing the problem to the mold.
These patterns narrow the checks; they do not prove a cause by themselves.
Check fill and packing evidence
Compare the current run with the approved setup and available pressure, position, cushion, temperature and cycle records. Confirm that the machine is supplying the required material consistently and that the flow path is not freezing or being restricted prematurely. Check whether air is trapped at the last-to-fill region. A part that appears filled may still be inadequately packed, so evaluate the agreed dimensions, weight or functional criteria as well as the visible edge.
Run a controlled corrective trial
Change a condition only after the evidence supports that line of investigation. Record the original condition, the specific change, cavity results and any side effects. Avoid changing multiple settings at once or applying a universal shot-capacity percentage, speed or temperature. Changes to fill, packing, venting, gate or material can affect other dimensions and defects; validate the complete acceptance criteria before releasing production.
Autodesk 的 short-shot troubleshooting reference lists flow restrictions, hesitation, inadequate venting, temperature, material delivery and machine defects as possible causes, and cautions that remedies can introduce other process problems. For related design checks, see DAYIN’s 澆口位置選擇指南 和 供方工藝控制指南.