The use of polymethylmethacrylate (PMMA) plates is limited by some of their typical features, particularly the tendency to be deformed when conjugated with other materials, while remaining stable if it becomes homogeneous. This paper describes PMMA deformation caused by injection molding at high temperature. The relocation of the injection gate in order to minimize the deformation is also studied. Results rule out residual stresses as the main cause of the deformation, which are predicted by inverse engineering as described in the paper. Further study of residual stresses among different injection gates is made, and deformations of the PMMA-touch screen panel (TSP) laminated plate based on the locations of the injection gates are measured. In conclusion, one of the ways by which to reduce deformation at high temperature is to locate the injection gate at a symmetrical position of the plate.