“…If thinner walls are better for structural and functional reasons, it is necessary to adjust the processing conditions, e. g. use a type of plastic with a higher MFI (melt flow index), to increase the temperature of the melting form or that of the mould, or, eventually, use multiple injections. [4,5] Large differences in the wall thickness of the mould result in uneven cooling, material shrinkage, and the formation of internal stress. This ultimately may give rise to deformations, such as those in form sink marks, and may affect the required quality of the mould.…”