Plasticizing stage. Screw Rod began rotating, then will from hopper conveying came of plastic to screw Rod front-end conveying, plastic in high temperature and shear force of role xià plastic of uniform and gradually gathered in material tube of front-end, with melting plastic of gathered, pressure increasingly big, last overcome screw Rod back pressure will screw Rod gradually back pushed, dang material tube qián Department of plastic reached by needed of injection volume shí, screw Rod stop back and turned, pre plastic stage ended of.