Injection molding defects can impact both the aesthetic and functional quality of a molded part. Three common issues are Flash, Sink Marks, and Short Shots. Understanding the root causes and corrective actions is critical for optimizing part quality, cycle time, and material usage.
1. Flash
Definition:
Flash is excess material that escapes from the mold cavity and solidifies along the parting line, ejector pins, or vent locations. It appears as a thin, unwanted layer or fin on the surface of the molded part.
Common Causes:
Excessive injection pressure
Worn or damaged mold components (e.g., parting lines, seals)
Improper clamp force
Misaligned mold halves
High melt temperature
Insufficient or improper venting
Troubleshooting & Solutions:
| Area | Action |
|---|---|
| Machine Settings | Reduce injection pressure or speed; lower melt temperature. |
| Mold Condition | Inspect and repair worn or damaged parting lines and sealing surfaces. |
| Clamp System | Increase clamp force to ensure proper mold sealing. |
| Venting | Improve or clean mold vents to prevent backpressure. |
| Alignment | Check and correct mold misalignment and platen parallelism. |
