Quality Improvement of an Injection-Molded Product Using Design of Experiments: A Case Study

Abstract

This paper was originated by a problem that occurred in an injection-molding project. The mold design team reported that the machine produced excessive flash on the molded part, the Bulldog, of Kettering University's mascot. The investigation of the manufacturing process problem required the understanding of many factors that influenced excessive flashing. After discussion and input from the team, a simple four-factor full-factorial design with duplicate measurements was used for the experiment. The analysis revealed that factors A (pack pressure), C (injection speed), and D (screw RPM) and also the interactions AC and CD were significant. The settings for A, C, and D were obtained. The confirmation runs showed that the setting of A at low level (150 psi), C at low level (0.5 in./sec), and D at high level (200 rpm) produced Bulldogs with zero flash.