Warpage simulation of plastic injection moulded parts using a multi‐point constraint approach

Abstract

The surface mesh defining the outer boundary of the part is used in the warpage analysis of plastic injection moulding. The structure is represented as a perfect bonding of two half‐thickness plates which are modelled as flat shell elements with their reference surfaces on the outer boundary of the part. Bonding is assured by multi‐point constraints. After analysing several popular constraint imposition methods of master‐slave elimination, penalty augmentation and Lagrange multiplier adjunction, a Lagrange multiplier based elimination method is proposed. By comparison with the experiments and Moldflow, the presented model shows a high performance in computation accuracy.

Keywords:

• Plastic injection moulding
• Warpage analysis
• Surface mesh
• Multi‐point constraint

The authors would like to acknowledge the financial support from the National Natural Science Foundation Council of China (Grant No. 50875095) and the National High‐tech R&D Program of China (Grant No. 2009AA03Z104).