Weld line is molten resin coming from different directions side on the part front place is cooling. Arising from in combination has not been fully integrated. Fusion occurs in the resin at the confluence area. Two resin flow meet place will be coming weld line. In the time, The weld line will be more obvious if the two resin flow temperature lower. Two resin flow mark will be no amalgamate during the plastic fusion. Few issues need pay attention during the injection.
- Temperature for the resin injection
The surface layer thickness will be more deep if the temperature is too low; lines mark very clearly and the plastic hardness will be reduces. the reason because the adhesion was become weakly. Opposite, If the resin flow temperature higher. The resin adhesion will be strengthen, part appearance weld line becoming obvious.
- Holding pressure for the injection.
Holding pressure low, the weld line more obvious, plastic hardness more low. We need think about how to set up the holding pressure. Because the pressure transfer to plastic will more difficult during the curing progresses.
- Runner position and size
The plastic melt surface appearance and hardness will be very bad if the runner position is un-correct or runner size too small.
- Air-vent. Position.
- Fusion is the resin of the confluence point，Also is the injection flow terminal. The plastic melt surface and hardness will be worsen if we have set up good are vent on this area.
How to improvement the weld line?
- Adjust injection condition, improve flow property. For example: increase resin temperature, increase the mold temperature. Increase injection speed and pressure.
- Add more vent slot, It’s good for vent set up push rod on the weld line area..
3 .Less use mold release agent
- Set up process of overflow and production of the weld marks. cut off weld marks area after injection.
- Change the weld line area place for less important part surface.
