Abstract: Based on the structural feature of feeding frames of printers and rheological characteristics of thermoplastic resins used, a three-plate mould with single cavity and three core pulling mechanisms were designed. The design skills were carefully analyzed, which include mould forming parts, gating system, fixed distance parting mechanism, side-core pulling mechanism, temperature control system, demoulding system and guiding positioning system. The deformation problem of side-core pulling plastic parts under a large tight force was solved by using a horizontal push rod. The precision of the injection-molded product reached MT3, the molding cycle was shortened by 8 % to 35 s compared with other same type of plastic parts.