The phenomenon that the surface of a molded product is dented due to shrinkage. It is often found in thick molded products.
- Small gates, sprues and runners
- Poor gate position
- Insufficient cooling time
- Overly high or low mold temperature
- Low injection/holding pressure
- Short injection/holding time
(1) Measures related to mold
- Lower the cavity surface temperature slightly.
- Enlarge gates and runners
- Make the sprue thicker.
- Reexamine the mold cooling circuit to improve cooling efficiency.
- Modify the cooling structure of the part that is hard to cool to a structure that is easy to cool.
(Example: Baffle plate structure, cooling pipe structure, heat pipe, non-ferrous metal nest)
- Increase the number of gates.
- Change the gate position to the thick part.
(2) Measures regarding injection molding conditions
- Increase the holding time.
- Set a higher holding pressure.
- Set the injection speed faster.
- Lower the nozzle temperature.
- Increase the measured value.
- Increase the amount of cushion.
- Try changing the injection molding machine.
- Allow sufficient cooling time
- Replace the backflow prevention ring of the injection unit.
(3) Measures related to molded product design
- Remove the thick part of the molded product.