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Views: 0 Author: Site Editor Publish Time: 2025-02-27 Origin: Site
Avoiding defects in injection-molded plastic parts requires a combination of good part design, optimal process settings, and well-maintained equipment. Here’s a detailed guide on how to avoid common injection molding defects, organized by defect type:
| Defect | Prevention Methods |
|---|---|
| Flash | - Increase clamping force to prevent mold separation. - Avoid excessive injection pressure. - Ensure proper mold alignment and maintenance. - Improve mold design to include proper venting and parting line fit. |
| Vacuum Voids | - Position gate near thicker sections to improve flow and packing. - Increase injection and holding pressure to eliminate trapped air. - Use lower viscosity material if possible. - Optimize venting and avoid sharp corners. |
| Delamination | - Use clean, uncontaminated raw materials. - Properly dry hygroscopic materials before processing. - Minimize or eliminate mold release agent use. - Increase melt temperature slightly to improve fusion. |
| Short Shots | - Increase shot size or material feed. - Increase injection pressure and speed. - Widen runners and gates to reduce flow resistance. - Reduce material viscosity by increasing melt temperature. |
| Discoloration & Burnt Marks | - Lower mold and barrel temperatures if overheating is suspected. - Increase injection speed to reduce residence time. - Clean barrel regularly to avoid material degradation. - Avoid dead spots in the flow path. |
| Flow Lines | - Increase injection speed and pressure to maintain consistent melt flow. - Avoid abrupt changes in wall thickness. - Improve gate and runner design for uniform flow. - Increase mold temperature slightly for better surface finish. |
| Sink Marks | - Use uniform wall thickness in part design. - Increase packing pressure and time. - Enhance cooling system, especially in thicker areas. - Avoid over-packing, which can create internal stresses. |
Part Design: Use uniform wall thickness and avoid sharp corners. Include proper draft angles for easier ejection.
Mold Design: Ensure balanced runners, adequate venting, and well-located gates.
Material Handling: Dry materials according to specifications, especially for hygroscopic plastics like ABS, PC, and PA.
Process Control: Monitor and fine-tune parameters like:
Injection speed
Pressure
Holding time
Cooling time
Mold temperature
Machine Maintenance: Regularly clean the barrel, screw, and mold surfaces. Check for leaks and mechanical wear.
Quality Checks: Use regular visual inspections and dimensional measurements to catch early signs of defects.
