Bull socket shell products are shown in Figure 1, there are two specifications, one large and one small. Maximum dimensions of large socket are 53.80 mm * 38.90 mm * 30.55 mm, average thickness of plastic part is 1.95 mm, material of plastic part is ABS + PC, shrinkage rate is 1.005, and weight of plastic part is 10.06 grams. Maximum dimensions of small socket are 38.90 mm * 17.90 mm * 30.55 mm, average thickness of plastic part is 1.95 mm, and weight of plastic part is 3.94 grams. Technical requirements for plastic parts are that there should be no defects such as peaking, underfilling, flow lines, pores, warping deformation, silver streaks, cold material, and spray lines.

 

Figure 1 Product picture of bull socket shell
Bull socket is a well-known electrical brand. As can be seen from Figure 1, plastic parts are divided into two types. Structure of two sockets is basically same, but length direction is different. Socket requires certain strength and mechanical properties, so it is designed and manufactured with plastic alloy.
Main points of socket plastic parts design:
1. Dimensional accuracy is high, installation dimensional accuracy of socket plastic parts is high, and accuracy of socket part is higher. Accuracy tolerance of square hole of golden finger of computer connector is 0.005, and center distance tolerance is also 0.005. General requirement is is that dimensional accuracy of hole distance between contacts should be maintained at level 6.
2. Drape: Plastic parts of electrical connectors must be avoided for tiny drape. Because any tip will fall into product and accumulate dust, causing poor contact or short circuit.
3. Material selection, material must have sufficient mechanical properties, creep will be small after being stressed, and it will not warp or deform after long-term use. After heating up, expansion is small. It has certain flame retardant properties.
Socket mold design points:
1. Number of cavities: Due to high precision of plastic parts, number of cavities is generally 1 to 4 cavities. No more than 4 holes at most.
2. Key points of inlaying: dimensional accuracy of inserts is high, and small inserts need to be ground, so inserts must be cut and fixed with a hanging table. Alcohol cooling is used for insert grinding to ensure dimensional accuracy. Insert hole is processed by slow wire cutting.
3. Steel selection: Ordinary inserts can be made of SKD61, and precision ground to size after heat treatment. Inserts with large cantilever size can be made of high-speed steel, such as SKH51, etc. In the case where particularly high elasticity and strength are required, it must be made of Swedish ASSAB steel Viking. Disadvantage is that price is very high, and it can only be used in export molds that require long life.
4. Because to maintain life of mold, socket mold must be designed with a hard mold.

 

Figure 2 3D mold design drawing
Before mold design, product must be analyzed first to determine a reasonable mold opening direction. For bull socket housing, difficulty in mold design is to determine mold opening direction of plastic part. Cavity design of mold is 2+2, and two plastic parts are arranged side by side in a Z shape. Narrow groove on the bottom edge of plastic part needs to design a slider to pull core, and slider is designed on the outside of mold. 3D mold design diagram is shown in figure 2.

 

Figure 3 2D mold structure diagram
Gating system of mold is a side gate, as shown in Figure 4. Mold base is standard mold base CI2730, and runners of two small products are arranged at 60°, which is convenient for rapid filling of molten plastic. Front and rear mold cores adopt secondary positioning of tiger's mouth to ensure accuracy of mold clamping.
Sliders of two sockets, big and small, are designed on same slider, and a slider insert is designed on the slider. Slider is a rear mold slider, which is driven by a T-shaped slot, and inclined wedge is extended into movable mold as a backhoe, which is an effective measure to prevent front from appearing.
Front mold adopts straight-through water transportation, and rear mold adopts a cooling method combining straight-through water transportation and ponds.
Plastic part has a relatively strong wrapping force on moving mold, so a flat thimble is designed on the edge of bone for ejection, and an thimble is designed on the rest of parts.

 

 

Figure 4 2D structure diagram