Tight tolerance thermoforming

Tighter tolerances are becoming more prevalent as thermoforming application s are increasingly utilized in multiple component assemblies with load bear ing and other functional capabilities. A, analytical method is described fo r shrinkage predictions utilizing a thermoviscoelastic constitutive model t o try and avoid costly and time consuming forming trials by determine adequ acy of the mold and process a-priori. Validation experiments and sensitivit y analyses were performed to understand the process behavior and estimate t he accuracy of the shrinkage analysis. Design and manufacturing guidelines it-ere then developed to facilitate tight tolerance thermoforming. While th e analysis was generally capable of predicting linear shrinkage, statistica l yield models indicated that improved process control and further process development is required to consistently produce thermoformed parts to tight tolerances.