CONTROLLING INJECTION MOLDING PARAMETERS FOR OPTIMUM PART PROPERTIES.

A study was conducted to identify the major molding variables which induce haziness and poor weld lines on thermoplastics parts. The mold that was constructed for the experiment had a variable length runner system and pressure transducers at the injection nozzle, sprue, fan gate, and cavity areas. It was found that one type of haze occurs in ABS when the molten plastic is not sufficiently compressed prior to cooling to the solid state. Haze and poor weld lines can be remedied by using faster injection rates, hotter mold temperatures, and the highest possible cavity pressure consistent with low residual stress in the molded part.