The product diagram of the motor mounting box is shown in Figure 1. The maximum size of the product is 209.48 mm x 168.40 mm x 138. 15mm, the average thickness of the plastic part is 2.40mm, the material of the plastic part is fireproof ABS, the shrinkage rate is 1.005, and the quality of the plastic part is 235.70 Grams. The technical requirements for plastic parts are that there must be no defects such as peaks, dissatisfaction with injection molding, flow lines, pores, warpage deformation, silver streaks, cold materials, jet lines, etc.
It can be seen from Figure 1 that the structure of the plastic part is relatively complex, with three undercuts on the outside and one undercut inside. The difficulty of mold design is the design of the four sliders. Other requirements for mold design are a mold life of 800,000 times, an injection cycle of 40 seconds, and an injection molding machine tonnage of 450 tons. The mold design requirements are shown in Figure 3 mold design specifications.
The size of the plastic part is large, and there are four slider cores. The mold design cavity rank is 1 out. 1. The mold base is a non-standard mold base 4550. The plastic material is ABS fireproof material, which is corrosive to the mold core. The mold core is made of 2316 steel and heat treated. The four corners of the front and rear mold cores are positioned by tiger mouths to improve the accuracy of mold clamping. The size of the front and rear mold cores is 250x290. Due to its large size and high height, the fine frame of the front and rear mold cores and the mold embryo are required to be matched, and the frame is difficult to match. Therefore, the compression block on the edge of the mold core is used to position the The tight block is designed on the two sides away from the base corner of the mold base.
Due to the large size of the mold, the clamping force of the front and rear molds is also very large, but the cavity of the front mold core is deeper, and the contact area of the front and rear mold cores is small, only the edge of the plastic part is in contact with the cavity. The parting surface is crushed, thereby blocking the vent groove of the parting surface and causing poor injection molding. In order to solve this problem, balance weights are designed on the four corners of the mold base, and the balance weights are installed on the movable mold B board, see mold design diagram 2.
The gating system of the mold adopts a single hot nozzle, and the glue is injected at a point on the top of the plastic part. The injection method of the gating system affects the injection cycle. Hot runner and hot nozzle injection can significantly speed up the filling process of molten plastic and effectively shorten the injection cycle.
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