Design of prestressing plastic gears

Plastic gears, which have low noise, lightness and self lubricated, are limited in their usage because of their low strength. The failure mechanism of plastic gears combined of fatigue, plastic deformation and creep behaviour. In this study, polyproplyene is selected because of being produced easily and economically. 3 different springs are placed in model of plastic gears. These springs are stretched before injection molding and then they are loosed to make pre- stressing. 142 specimens are prepared in this study. 58 ones of these specimens havee been observed of pores while performing experiments. The results of experiments 84 samples showed that plastic gears, it is concluded that strength values increase with springs reinforcement When wire diameter and pre- stressing increasing, service life of reinforcement sample is approxitamely 30 times more than service life of unreinforcement sample. At pre-stressing samples have %10 more strength than unreinforcement samples on constant number of cycles.Key Words : Plastic gear, pre-stressing, fatigue, reinforcement with spring