How to solve injection mold weld line and bumps near the weld location?
Weld lines in a molded product are due to the following
1. Less mold temperature
2. Less barrel temperature
3. Less back pressure
4. Less injection pressure
The above factors are common and the following are common in new molds
5. Improper vent design
6. Improper flow of melt in side the mold (improper location of gate)
These weld lines can be rectified by
1. Increasing the mold temperature such that the melt don't freeze until it unites.
2. Increasing the barrel temperature reduces the viscosity of the melt and there by makes the flow inside the easier and unites with melt.
3. Increasing the back pressure and injection pressure can solve weld line problems due to low pressure.
4. Sometimes weld lines in new molds arise due to improper venting so improvement in venting near the weld line region eliminates the weld line in the form of flash.
5. Improper location of gate point leads to unsymmetrical flow, so gate points to be set in such a way that the melt flows equally in all directions.