Injection mould defect analysis-weld line, material flow line
- Appearance of the weld line
Weld line often appears in the place which every fluid meet. Especially in the high-polished surface in mould, weld line in the plastic product just like a mark or slot, it is obviously in the plastic products with dark color or transparent plastic molding products. Weld line’s location is always depending on the material flow direction.
- Physical reason of the weld line
The location of weld line is where melt material separate but connect again area. It will form weld line and material flow line in the place two melt material meet again. The bigger core around melt material is, the more obvious the melt line will be. But the small weld line will not affect products quality and strength.
However, if the flow distance is too long or the pressure is not high enough, inadequate filling will lead to a slot. The quantity of gate and the location of gate also determine the weld line’s quantity and location. The smaller fluid -striker angle is, the more obvious the weld line will be.
In most circumstance, technology debugging cannot solve weld
line or material flow line. We can reduce their brightness, or move them to invisible or inconspicuous place.
- Reasons connecting to the machining parameter and improvement
| Injection speed is too slow | Increase the injection speed |
| Mold wall temperature is too low | Increase the mold wall temperature |
| Mold temperature is too low | Increase the mold temperature |
| Pressure is too low | Increase the pressure; change the pressure as soon as possible |
- Reasons connecting to the design and improvement
| Unreasonable gate position | Resetting gate position and move it to position which is not visible |
| No venting hole in material flow runner | Venting hole size should meet the material characteristic(ABS:0.02mm depth,PA:0.01 depth) |
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