The Research On Key Issues Of Polyurethane Rubber Micro-punching Mould

With the rapid development of micro-electromechanical system, the demand for precision instruments was increased, miniaturization and fast high-precision manufacture have become the research focus. Micro-blanking technology, a new plastic molding technology, will have a broad application prospects in the aerospace, precision electronic equipment, bio-medical and other fields because of its high precision and production efficiency.The polyurethane rubber blanking technology is often used in the sheet punching, especially the thickness of sheet less than0.3mm. The punch or die of this mould is replaced by polyurethane rubber elastomer. The production cost of the mould is low and the cycle is short, the forming characteristics determine the pieces have good surface quality. It will greatly reduce manufacturing costs and improve production efficiency if this technology is used for micro parts production.This paper summed up the design features of the polyurethane rubber blanking die based on the analysis of forming mechanism. The type of mold must chose casting polyurethane with the hardness of90A above, and interference installation in the container box, the amount of compression should not be greater than30%. The chamber should be carried out to strength check, ensure it can withstand the expansion force caused by formed rubber. The binder type of mould is also the key factor of blanking.This paper designed micro-mould according to the shape characteristics of the small parts with micro structure feature, and checked the ability of the mould on the pressure and bending stress. For numerical simulation of sheet blanking, the polyurethane rubber micro-blanking mould analytical model was established in ABAQUS/Explicit. Johnson-Cook constitutive model and fracture criterion of T2were established. Set up uniform load instead of interaction between the polyurethane rubber and sheet metal. The paper analyzed breaking law during sheet metal blanking process, and the right angle on micro structure is the last break location. The compressive stress of sheet material is increased with the increased punching speed.Reduced the height of polyurethane die. adopted ladder binder type, solved the problem that the micro structure of piece was incomplete. At last, get the pieces with micro structure which features size was100μm successfully, and the surface quality was good. Experimental results showed that, there is a size difference between the piece and punch, the size of punch less than dimensions of piece, the size difference is reduced with the reduction of the sheet metal’s thickness, but the ratio of the difference in size and the thickness of the sheet metal increases, so the bending deformation is getting worse.