A welding line is the line created when two flow fronts meet. The fronts don’t weld or knit themselves together properly, which causes locally weak areas in the product.
A welding line occurs when the mold or material temperatures are set too low, so that the materials are too cold when they meet to bond perfectly. Another way welding lines form is when oxide forms on the corner of the weld preparation. If the welding arc can’t reach the area to clean the oxide, the welding line appears.
Prevention is best; if welding lines can be prevented, then they don’t need to be removed. However, if a welding line is causing a weak area, a deburring robot can come to the rescue!