The 8 kg gimbal of the automatic washing machine is an important part of the top of the inner drum of the automatic washing machine. The product picture is shown in Figure 1. The maximum size of the product is ø474.60 mm x 27.64 mm, the average thickness of the plastic part is 3.46 mm, the material of the plastic part is PP+GF8, the shrinkage rate is 1.013, and the quality of the plastic part is 584 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, bubbles and so on.
Adding 8% glass fiber to plastic parts can increase wear resistance and fatigue strength, and can increase electrical properties. It can be seen from Figure 1 that the plastic part is shaped like a big circle. Inside the circumference, 2 circles of circular bone positions and 24 radial reinforcement ribs are designed along the radius, and 3 screw holes are evenly distributed along the circumference.
The size of the plastic part is large, and the mold design cavity arrangement is 1 out. 1. The glue position of the fixed mold part is directly out of the mold base, and the circular insert of the movable and fixed mold is a mosaic structure. The mold base is a non-standard mold base DDI7070. In order to increase the clamping area of the movable and fixed molds and increase the stability of the mold, a balance block is designed at the four corners of the mold base and fixed on the side of the movable mold. A taper positioning block is designed at the center of the four sides of the mold base to increase the accuracy of mold clamping. See mold design drawing 2.
Round plastic parts made of PP material are prone to deformation during injection molding. Deformation is often related to the way of glue feeding. When the gate is selected in the center of the plastic part, the deformation will be more obvious. Therefore, the gate of this set of molds did not choose the side gate to feed the glue from the center of the plastic part. The gating system is designed with 4 point gates, as shown in Figure 3.
Plastic parts have many bones, and the tightening force on the movable mold is relatively large. If the ejection is unbalanced, the plastic parts will be deformed. To this end, a push plate ejection is designed. The parting line between the push plate and the mold core is 0.3 mm from the inner edge of the product to avoid friction between the push plate and the movable mold core, as shown in Figure 4.
The water transport design of the moving and fixed molds fully considers the uniform cooling of the mold. The fixed model is designed with an arc-shaped straight-through water, and multiple ponds are designed on the loop to speed up the cooling efficiency. The movable model also designed an arc-shaped straight-through water, and designed multiple ponds on the loop. In addition, the movable mold is designed to transport water through a hexagonal shape outside the shape of the plastic part.
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