Weld Lines

Design Course

Designing of Plastic Products for Injection Moulding

Manufacturing Methods and Technologies

Prof. Vijay. P. Bapat and Shiv Kumar Verma

IDC, IIT Bombay

Weld Lines

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Attachment	Size
lecture-weldlines.mp4	100.07 MB

Weld lines are the regions where two melt front meets and bond during filling of a part. Weld lines occurs when melt fronts are forced to go around an obstacle like a hole and then they meet or when the melt front coming from two different gates at opposite ends of a part meet together. Since the temperature at the melt front is lower than the temperature of the melt entering into the mold the bonding at the weld line is weak thus strength in the weld line area is reduced.

Design considerations

Locate weld line in structurally non critical areas, in aesthetically non critical area.
Use proper texture if possible to hide weld lines.
Locate weld line in the area where thickened ribs can be used.