Product diagram of explosion-proof lamp body is shown in Figure 1. Maximum external dimension of product is 118.16 mm * 106.00 mm* 59.00 mm, average thickness of plastic parts is 1.50 mm, material of plastic parts is PA+15%GF, shrinkage rate is 1.0105, and weight of plastic parts is 44.50 grams. Technical requirements for plastic parts are that there shall be no defects such as peaks, underfillings, flow lines, pores, warpage deformation, silver lines, cold materials, and spray lines.

 

Figure 1 Product diagram of explosion-proof lamp body
As can be seen from Figure 1, plastic part is shaped as a square closed shell with large rounded corners at four corners, edge is a double-layer structure, and there are multiple reinforcing ribs between two circles. There are multiple juxtaposed shallow bones on inner top of plastic part. There is an installation position on the outside of plastic part, and inner hole needs to be designed with a slider core pulling mechanism. Plastic parts have same main structure, and a series of plastic parts with different parts share mold, and there are 6 parts with different parts. See 3D drawing. In interchangeable part, a series of interchangeable inserts are designed, inserting positions are shown in parting surface analysis diagram of Figure 3.
Mold design cavity ranking is 4 cavities, and mold base is a non-standard mold base 5070. Since mold adopts a hot runner system, a multi-cavity hot runner system needs to design a manifold, so fixed mold part is different from standard mold base. For positioning of mold base, fixed mold is positioned by flipping guide column on panel. Movable mold is positioned using guide post, guide sleeve and positioning pin, and adopts style of HASCO mold base.
Fixed part of hot runner mold is usually not separated by a template, which is inconvenient to design fixed mold slider core pulling mechanism. In this case, oil cylinder core pulling is often used.

 

Figure 2 Parting surface of explosion-proof lamp body

 

Figure 3 Mold Design Ranking Diagram
When designing and ranking mold, 4-cavity core-pulling parts need to be combined and arranged in the center of mold. Plastic parts of this set of molds require two sliders to be separated, which are similar to Huff sliders. Since there is no space inside mold to accommodate core pulling of oil cylinder, mechanism of bending pin core pulling is adopted. See Figure 4. Slider is a fixed-mode tunnel slider, shovel is fixed on hot nozzle fixing plate, slider and slider seat are fixed on A plate. Mold plate is separated to complete core-pulling action, and button machine is used to realize sequential typing. When hot nozzle fixing plate is separated from A plate, hot nozzle cover (including hot nozzle) is separated from A plate. Bent pin utilizes 3-point positioning to increase its rigidity. Head of bent pin and B plate use inclined plane to realize backhoe. Because position space of slider in the middle is limited, shovel adopts T-slot drive.
PA+15%GF material has anti-aging and wear-resistant properties, and has high mechanical strength. Mold temperature is high during injection molding. For hot runner molds, temperature adjustment system of mold is very important. For this reason, a heat shield is designed on fixed die base plate to prevent heat exchange between die and injection molding machine. Both movable and fixed molds are designed with straight-through water transport to improve cooling efficiency.
Central part of plastic part belongs to optical function part, and ejection marks cannot be designed. Therefore, ejector adopts method of designing thimble at bone position of product diagram, and ejector is designed at 4 column positions. When temperature of mold is high, there must be a gap of more than 0.1 on one side between top of bushing and back of B plate. Material of bushing is graphite copper. Ejection of mold adopts European style, that is, return pin is not covered with a return spring, and ejection insert installed under bottom plate of ejector is used to eject it. There are threaded holes at the bottom of ejector inserts. Generally, different threads are used according to size of mold. M12, M16 and M20 are commonly used for metric molds. Ejector stick of injection molding machine cooperates with this threaded hole to pull ejector plate to eject and return. This ejection method is usually called strong pull and strong ejection.

 

Figure 4 Analysis of die slider mechanism
Fxing method of cylinder needle of precision mold must be pressed by pressure plate, method of pressing and fixing by Kimi screw should not be used as much as possible. Because of way Kimi screw is compressed, height dimension of cylinder needle is difficult to control.