Research On Key Technology Of In-Mold Assembly Injection Molding Of The Micro Plastic Hinge

For the key technology research on in-mold assembly injection of micro plastic hinge, the purpose is to make this type of products break away the strait of high cost, in order to smooth out the way of the micro plastic mechanics from laboratory research to practical application. The methods include reducing equipment costs by avoiding the high-end injection molding machine, innovating the product design and the mold design, reducing production steps by avoiding the secondary treatment of assembly work after demoulding. Based on preliminary research of in-mold assembly technology, this thesis made further study on inducing the ice cold trick into the injection mold of micro plastic revolute joint. By using the semiconductor refrigeration technology, an ice cold system was developed to make the tiny core rapidly cool down, in order to eliminate adhesion of the contact areas between the micro plastic hole and the micro plastic pin which compose the micro plastic hinge while shortening the producing cycle time greatly.At first, the thesis summed up previous research about molding sequence and the fit clearance of parts composing the micro plastic hinge. After analyzing successful application of the ice cold trick to in-mold assembly of micro plastic mechanics whose components are made of the same polymer material, both possibility and difficulty about using the ice cold trick for in-mold assembly of a micro plastic hinge which is also made of the same polymer material are discussed.Secondly, a practicable program was proposed which can extremely cool the tiny core and then make polymer melt touching the tiny core rapidly cool down. This program includes inlaying the semiconductor refrigerating chip into the key location of the mold, using the heat pipe as heat-conducting approach, and properly designing insulation structure and the cooling unit. A temperature control system was designed for in-mold assembly of a micro plastic hinge which is made of the same polymer material from a single cylinder injection machine. Temperature distribution was calculated by means of ANSYS Workbench steady state thermal analysis and design of the ice cold system was optimized.Thirdly, the ice cold system was installed into the mould for a micro plastic hinge which is made of the same polymer material (HDPE). In the running system, double flow channels were used for conversion between molding processes of the micro plastic hole and the micro plastic pin. Through many tests by trial and error, quality defects of the plastic parts were eliminated.Finally, experimental products of the micro plastic hinge made of the same polymer material (HDPE) were disassembled, and the micro plastic holes and the micro plastic pins were observed. Measuring of the key dimensions showed that the micro plastic hinge produced with ice cold system had reliable quality and reasonable fit clearance, and at the same time the injection molding cycle times was shortened effectively.