What is weld lines in injection molding  During the manufacturing of injection molding process , the Weld lines , also calles as Knit lines or Meld lines are present on the surface of plastic molded parts where two flow fronts meet and when they are not able to to “knit” together, or “weld” together .These harilines or dark lines usually occur around holes or obstructions and cause locally weak areas in the molded resin part. Appearance of weld lines in injection moulding  Notches, hairlines Change in apparent color; especially when inorganic decorative effect pigments are used the weld line appears as a dark line; conspicuous in dark, brilliant or transparent moldings having smooth surfaces polished to a high gloss. Cause of weld lines injection molding Appear in multiphase systems such as ABS or ASA. Flow fronts having an already cooled peripheral layer encounter one another and no longer allow fusion without marks. Decorative effect pigments and, e.g., glass fibers tend to straighten up in the…