7 Common Injection Molding Defects and How to Avoid Them
Defects can be costly! Especially in the production process. Here is a small insight into some common defects in injection molding.
1. Burn Marks:
The occurrence of a blackened edge near the end of the cavity-filling process
| Causes | Solution |
| Incorrect Injection Speed | Reduce and regulate the injection speed |
| High Resin Temperature | Examine and monitor the resin temperature regularly |
| Incorrect Venting and Gating | Make the needed corrections in the design to place the Venting and Gates at the right place |
| Wearing of Screw and Barrel | Regularly replace the Screw and Barrel to avoid complete wear and tear |
2. Surface Delamination:
Delamination in injection molding refers to a defect where thin layers or flakes appear on the surface of the molded part, which can often be peeled off.
| Causes | Solution |
| Contamination of plastic resin | Proper storage of the resin |
| Mold temperature too low | Temperature and Cooling Time has to be monitored |
| Excessive Moisture | Appropriately dry materials before molding to remove moisture. |
3. Vaccum Voids:
Trapped air pockets are known as air voids or vacuum voids
| Causes | Solution |
| Low injection pressure |
Proper Venting and gating |
4. Discoloration:
When the finished plastic product is a different colour than it is supposed to be.
| Causes | Solution |
| New product made from leftover pellets from the previous production. | Not using the leftover pellets from the previous running of machining |
| Residual material stuck in the nozzle or mould due to low pressure. | Regular removal of any excess colour and residual material |
5. Warping:
Warping occurs when different parts of a product cool and solidifies unevenly during plastics processing.
| Causes | Solution |
| Premature cooling rates | Make the cooling process gradual Adjust the mould temperature |
6. Flash:
The thin layer of plastic forms when two different mold surfaces meet to create a boundary.
| Causes | Solution |
| Low clamp force | Regulate clamp force at the control |
| Gap within the mold | Make sure excess injection is not done |
| Incorrect Injection parameters | Monitoring of the injection process at every run of the machine |
7. Sink Marks:
Sink marks are slight depressions or irregularities that appear during the cooling and solidification phase of injection molding.
| Causes | Solution |
| Incorrect Melt Temperature | Adjust the melting resin within the recommended temperature |
| High mold temperature | Use of the right temperature |
| Low Pack and Hold time | Ensure the gates are solidified |
Conclusion:
The mentioned imperfections, as well as additional ones, could lead to financial losses if manufacturers do not prevent them. The most important ones are the ones already pointed out. Preventing these issues from happening is the sole method to guarantee a seamless production process.
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