The polymer gears are widely used as basic motion transfer elements in many industries. Continuous improvement on the quality performance of polymer gears is very important for their ability to meet present demand. So that, controlling the parameters setting in polymers gears are very importance in order to get the best gears quality. In this study, the influences of injection moulding processing parameters on shrinkage of polypropylene gears was investigated by using Taguchi approach. It was found that the optimal processing parameters for addendum circle shrinkage, dedendum circle shrinkage and tooth thickness shrinkage are A1B1C3D3E1F2G3, A3B1C3D3E3F1G3, and A1B3C3D2E3F2G1 respectively. This results showed that pattern of fluctuation showed either an improvement or reduction in quality characteristics upon the change of process parameters setting. © Published under licence by IOP Publishing Ltd.