Study on Optimization Design of Precision Double-shot Molding for Automobile Sealing Shell

The mechanical sealed shell is made up of three parts: metal, hard rubber and soft rubber, and the service life of the mold is more than 1 million times. Before injection, the precast metal parts are embedded in the mold cavity of the injection molding hard rubber. The first injection was made of hard rubber material nylon material (PA66+30GF). After molding, the hard rubber part completely wrapped the metal part. After the mold is opened, the semi-finished product of the first injection molding is moved to the second injection position through a manipulator. The second injection uses soft rubber material thermoplastic elastomer TPE (TC6 ABZ) to fill the sealing material for the first injection of the semi-finished skeleton, buttonhole and so on. Considering the requirements of high dimensional precision, complex structure, long die life and product price economy after two molding of the car seals shell, the software based on NX 10 and ASM 2014 is considered. In this paper, a mold design method which widely applies CAD/CAE technology is put forward. It carries out optimization design research through the combination of simulation and experimental analysis. First, we use NX 10 to create the 3D solid of the sealed shell. The ASM 2014 is used to simulate the gate location and filling of the sealing shell, so as to determine the overall injection plan. Then using the NX 10 injection mold design guide, the mold cavity layout, classification design, mold frame system, casting system, cooling system, the slide block and core pulling, standard parts are constructed to complete the 3D design of the mold. Then, the warpage of the seal part of the sealing shell is specified as the optimization target. The constraints of gating system and cooling system are set up, and the optimization variables are six injection molding parameters, which are cooling time, die temperature, speed/pressure switching, filling pressure, injection time and melt temperature. The orthogonal experimental method was used to evaluate and optimize, and the optimal molding process parameters were determined to be the 20s. The mold temperature is 45 degrees, the speed/pressure is switched to 8MPa, the filling pressure is 45MPa, the injection time is 15s, and the melt temperature is 280 C. The influence of process parameters on the warpage of injection molding is: melt temperature (54.1035%) die temperature (26.9066%) cooling time (9.20098%) injection time (4.41402%) filling pressure (3.28692%) speed/pressure switching (2.90396%). Finally, the trial production verification is carried out in the enterprise workshop, and the injection molding process parameters are set according to the optimization plan. Five groups of samples were extracted, and the overall good rate of the sealed shell was 100%. The conclusion was obtained that the orthogonal test method was suitable for optimizing the injection molding process and reducing warpage.