Effects of Process Parameters and Two-Way Interactions on Sink Mark Depth of Injection Molded Parts by Using the Design of Experiment Method

Abstract

Sink mark is one of the flaws occurring on the surface of injection-molded parts caused by inappropriate mold design and process parameters. Sink marks are often quite visible and significantly impair the surface quality of the parts. In this reports, an L27(3¹³) experimental matrix designed based on the Taguchi method was conducted to investigate the effect of process parameters and two-way interactions on sink mark depth of injection molded parts, and to minimize the sink mark depth. The relative significance of each processing parameter on the sink marks was analyzed using analysis of variance (ANOVA) and F-test. A plate cavity with bosses of various thicknesses was used in the investigation. Experiments were carried out on a CJ80E II injection-molding machine, and sink mark depths were measured by a movable bridge 3D COMERO. For the factors and interactions selected in the main experiments, the boss thickness and melt temperature were found to be the principal factors affecting sink mark formation in injection-molded parts. Experimental investigation can help to understand the formation mechanism of sink marks, and to optimize the surface quality of injection-olded parts.

Keywords:

• Design of experiment
• Injection molding
• Process optimization
• Sink mark
• Two-way interaction

5. ACKNOWLEDGMENTS

The authors would like to express their gratitude to the National Engineering Research Center for Advance Polymer Processing Technology of Zhengzhou University in China, for the funding support of ‘Major Research Plan of National Natural Science Foundation of China (10590352)’ and ‘General Program of National Natural Science Foundation of China (10372095)’.