Polypropylene PP is one of the more widely used varieties of general-purpose plastics, with the advantages of low density, good rigidity, impact resistance, chemical corrosion resistance, easy processing and good insulation, has been widely used in the chemical industry, chemical fibers, construction, light industry, home appliances, automobiles and packaging and other industrial fields, is a very promising thermoplastic. Although polypropylene has good comprehensive performance, but the molding shrinkage rate is generally 1.5%-2.5%, compared with the molding shrinkage rate of 0.4%-0.6% of ABS is much larger, in the processing of precision parts are subject to great limitations.