Birefrengent Residual Stress and Improved Injection Mold Design

Abstract:

Efficient manufacturing requires consistency. Automated equipment is designed to accept a small range of input variability and quickly sort and process for next steps. A case study for injection molding of polyethylene terephthalate preforms for use in stretch-blow molding was presented. One convenient method for measuring stresses in optically transparent birefringent parts is photoelasticity. Using cross-polarized light, fringes proportional to the stress state were observed. Faster cooling improved the residual stress state in the injected preforms. The improvements were both in magnitude, as represented by the frequency of fringes and consistency, as represented by the improved symmetry of the fringes. Lower pressure in the mold also aided in improving the residual stress state. Reducing the pressure needed to inject was accomplished by increasing the vent width.

• Periodical: Materials Science Forum (Volumes 768-769)
• Pages: 217-223
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.768-769.217
• Online since: September 2013
• Authors: Jay C. Hanan
• Keywords: Injection Mold, Photoelasticity, Polyethylene Terephthalate, Residual Stress

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