Part Details Review
| Weld Lines |
Weld lines are formed when separate flow regions merge and literally form a weld. This happens when two melt fronts originating from two gates meet or when a single melt front meets an obstruction, divides into two or more flow paths and reunites after passing the obstruction. For example, a core which forms a hole or window in the part would act as a flow-dividing obstruction.
Sometimes the obstruction can simply be caused by a partial but abrupt wall thickness reduction that only affects part of the flow. A surface defect, in the form of a line, or gas trap appears in the region where the full flow and the retarded flow meet.
Often flow fronts come together at an angle rather than head on. When the angle formed between the merging flow fronts exceeds a critical angle, typically about 90 degree for most Bayer materials, the weld line disappears from the part surface.
