Key Points Of Injection Mold Design For Bottom Shell Of Dynamic Monitor + 3d Drawing

The bottom shell of the dynamic monitor is shown in Figure 1. The maximum dimension of the product is 35.77 mm x 13.00 mm x 15.00 mm; the average thickness of the plastic part is 0.80 mm, the material of the plastic part is PC + ABS, the shrinkage rate is 1.004, and the weight of the plastic part is 4.30 grams. The technical requirements for plastic parts are that there should be no defects such as peaking, injection dissatisfaction, flow lines, pores, warping deformation, silver streaks, cold material, and jetting lines, and meet ROSH environmental protection requirements.

It can be seen from Figure 1

that the overall shape of the plastic part is complex, and there are 6 buckles on the back edge, which requires the design of a slanted top or a slider for molding. There are circular structural elements on the top surface of the plastic part, and it is necessary to design the shape of the Huff slider. In addition, there is a round hole on the side of the big head of the plastic part, and it is also necessary to design the slider for molding. From the comprehensive analysis, it can be concluded that although the plastic part is small, its structure is complex, and it is not easy to design a reasonable mold structure.

The 3D drawing of the mold design is shown in Figure 2.

The mold design cavity arrangement is 1 out of 2, and the two plastic parts are arranged in a straight line, mainly for the convenience of designing the slider. See Figure 3. Attention should be paid to the arrangement of the mold design, and the round holes at both ends should be arranged on the outside, so as to facilitate the separate design of the slider core-pulling. Difficulties in mold design lie in the analysis and arrangement of sliders, the mutual cooperation of several sliders when they intersect, the angle of penetration between sliders and the front mold, etc.

Gating system design is an important part of mold design. The gating system design includes the selection of the main channel, the determination of the cross-sectional shape and size of the runner, the selection of the gate position, the determination of the gate form and the cross-sectional size of the gate, and the design of the cold cavity. Before designing, a comprehensive analysis should be made on the material, size, geometric shape and possible defects of the plastic part, the appearance requirements of the plastic part, the production batch, and whether to use automatic injection molding production, etc. The shape of the plastic parts is all the appearance surface, and the gate can only be designed in the shape of a disc. The gate will be covered after assembly here, and the appearance of the plastic part will not be affected. The gate is a point gate, and the glue enters at one point.

 

The gate design is shown in Figure 3.

In the injection molding process, the plastic melt enters the mold cavity through the gating system. The type of gating system determines the mold structure to a certain extent. For example, two-plate molds and three-plate molds correspond to different gating systems. The quality of the gating system design has a very important impact on the quality and production efficiency of the injection mold. If the cross-section of the runner is too large, the plastic consumption will be high and the cooling time will be long; if the cross-section of the runner is too small, it will cause too much pressure drop, resulting in insufficient pressure when filling the cavity. In addition, the small runner cross-section can degrade the polymer due to excessive viscous heat. Therefore, it is necessary to reasonably select the cross-sectional shape and size of the runner and the length of the runner. For multi-cavity injection molding, it is necessary to reasonably arrange the arrangement of the main channel and the runner, the size of each section, and the size of the gate to ensure that each cavity is filled with the same pressure at the same moment. For multi-gate single-cavity molds, different gate sizes and gate positions as well as different runner systems will change the position of the weld line, thereby affecting the mechanical properties of the plastic part. Regardless of the layout of single-gate single-cavity, single-gate multi-cavity, multi-gate multi-cavity, and multi-gate single-cavity layout, correct and reasonable gating system design is very important.