Development of warpage simulation for rotationally moulded parts and the analysis of process parameters

There are multiple factors that contribute to the warpage problems where molten part is distorted during solidification in rotational molding. A novel warpage simulation model is developed accounting for the effect of various process parameters like crystallinity change, temperature-dependent polymer properties, and cooling rate. The polymer material properties were readily not available; they were constructed from literature data with adaptation to the process condition and their significance on simulation results is discussed in detail. A systematic detailed simulation analysis of warpage in box part was done and results were compared with experimental values published in literature. The warpage magnitude under seven different cooling methods are presented. It was found that externally water cooled parts exhibited maximum warpage which is also corroborated by literature data while the parts cooled by water on either sides of the part show reduction in warpage. The warpage simulation results show an agreement with deviation ranging from 1.2% to 69% with experimental values. Highlights * A novel thermal expansion coefficient approach was adopted for the first time to develop warpage simulation of rotationally moulded parts. * Inclusion of temperature-dependent thermo-mechanical properties of polymer in the simulation model. * The cooling rate is directly proportional to the warpage in the parts. * Validating warpage simulation results for seven different cooling methods with experimental measurements. * Maximum warpage is seen where the highest temperature difference exists between part and mould. KEYWORDS process parameters, rotational molding, shrinkage, simulation, warpage
1 | INTRODUCTION Control and prediction of warpage problem in rotational molding (1) of polymer parts is long overdue. All thermoplastic processing methods inevitably include heating the polymer to the [...]