Common problems and solutions of injection mold in the process of mold test

Improper mold design often leads to defects in the final product. Therefore, before mold modification in injection mold processing, it is usually necessary to test and evaluate the mold, optimize mold design and process parameters, so as to avoid unnecessary errors, achieve twice the result with half the effort, and meet the high quality requirements of mass production.

Most of the defects of molding products are caused in the stage of plasticization and injection molding, but sometimes it is also related to improper mold design. The possible influencing factors include the number of cavities, the design of hot and cold runner system, the type, position and size of injection inlet, and the structure of the product itself. Therefore, in order to avoid product defects caused by mold design, it is necessary to analyze the manufacture, design and process parameters of the mold.

1、 Poor surface gloss

Solution and order:

1. Material drying treatment → 2. Check whether the material is polluted → 3. Increase the material temperature → 4. Increase the injection pressure → 5. Increase the mold temperature → 6. Polish the mold surface → 7. Increase the size of sprue and gate

2、 Dents in sample

Solution and order:

1. Adjust the feed rate → 2. Increase the injection pressure → 3. Increase the injection time → 4. Reduce the material speed → 5. Reduce the mold temperature → 6. Increase the vent hole → 7. Increase the sprue and gate size → 8. Shorten the sprue length → 9. Change the gate position → 10. Reduce the injection pressure → 11. Increase the screw back pressure

3、 The sample has bubbles

Solution and order:

1 material drying treatment → 2 material temperature reduction → 3 injection pressure increase → 4 injection time increase → 5 mold temperature increase → 6 injection speed decrease → 7 screw back pressure increase

4、 Mold sticking of main runner

Solution and order:

1. Polish the main runner → 2. The nozzle coincides with the mold center → 3. Reduce the mold temperature 4. Shorten the injection time → 5. Increase the cooling time → 6. Check the nozzle heating ring → 7. Polish the mold surface → 8. Check whether the material is polluted.

5、 Difficulty in demoulding sample plastic parts

Solution and order:

1. Reduce the injection pressure → 2. Shorten the injection time → 3. Increase the cooling time → 4. Reduce the mold temperature → 5. Polish the mold surface → 6. Increase the demoulding angle → 7. Reduce the gap at the insert

6、 Poor stability of sample size

Solution and order:

1. Change the barrel temperature → 2. Increase the injection time → 3. Increase the injection pressure → 4. Change the screw back pressure → 5. Increase the mold temperature → 6. Decrease the mold temperature → 7. Adjust the feeding amount → 8. Decrease the return proportion

7、 The sample has surface ripple

Solution and order:

1. Adjust the feed rate → 2. Increase the mold temperature → 3. Increase the injection time → 4. Increase the injection pressure → 5. Increase the material temperature → 6. Increase the injection speed → 7. Increase the size of sprue and gate

8、 Sample plastic deformation

Solution and order:

1 reduce the mold → 2 reduce the material temperature → 3 increase the cooling time → 4 reduce the injection speed → 5 reduce the injection pressure → 6 increase the screw back pressure → 7 shorten the injection time

9、 Peeling and layering of sample plastic parts

Solution and order:

1. Check the type and grade of plastic → 2. Check whether the material is polluted → 3. Raise the mold temperature → 4. Dry the material → 5. Raise the material temperature → 6. Reduce the injection speed → 7. Shorten the gate length → 8. Reduce the injection pressure → 9. Change the gate position → 10. Use the big hole nozzle

Finally, it should be emphasized that the purpose and focus of mold testing is to optimize the mold and process to meet the requirements of mass production of injection mold processing, rather than just test out good product samples. This is why the importance of die testing in the later stage of mold manufacturing.