Product diagram of smart laser signal source housing is shown in Figure 1. Maximum size of product is 183.43 mm * 124.68 mm * 31.77 mm, average thickness of plastic part is 2.0 mm, plastic part material is PP, shrinkage rate is 1.015, and weight of plastic part is 56.49 grams. Technical requirements for plastic parts are that there must be no defects such as peaks, underfilling of injection molding, flow lines, pores, warpage deformation, silver streaks, cold materials, jet lines, bubbles and so on.

 

Figure 1 Product diagram of smart laser signal source housing
It can be seen from Figure 1 that plastic structure is a flat rectangular box with a lid on one end. Box and lid are connected together by a plastic hinge. Upper and lower two large planes of box are equipped with multiple heat dissipation grooves. There are two large square holes on one side of box, and one side hole on the other side needs to be designed with lifter molding.
Plastic hinges use characteristics of certain plastics. These plastics are commonly PP, PE, and some brands of PVC and ABS, etc., which can be directly made into plastic hinges. Cross-section of plastic hinge should be appropriately thinned, generally 0.25~0.4mm. For products with hinges, attention should be paid to selection of gate position, that is, flow direction of melt is required to be perpendicular to axis of hinge. In a multi-cavity mold, gate should be located on the side close to hinge to avoid weld marks in hinge area.
Length of hinge part should not be too long, otherwise bending line is not in one place, box and lid are misaligned, and closing effect is not good. Transition of wall thickness reduction shall be in a circular arc. Pay attention to machining accuracy when making mold, so that thickness of hinge part is uniform. And mold temperature here must also be kept consistent, otherwise it will reduce its bending life. After injection mould is out of mould, bend it several times and fasten it to cool it down to prolong service life of hinge.
Difficulty of mold design is analysis of mold opening direction, and then determination of parting surface. There are two possible mold opening directions for smart laser signal source housing product, and specific molds can be designed with these two solutions.

 

Figure 2 Mold diagram of shell of intelligent laser signal source
First mold opening direction of mold design is design of laying down plastic part horizontally. At this time, it is necessary to design three sliders, one side is a large slider, the other side is two small sliders, and middle one is lifter. See Figure 2. In this design scheme, in addition to lifter ejection, movable mold at mouth of box is added with a straight top, and a small ejector pin is added in heat dissipation groove.
Second method of mold design is to design mold by erecting plastic part so that two large planes containing heat dissipation groove are located on two Hough sliders.
Small square hole at lifter belongs to front mold small slider, which is sandwiched between two Hough sliders and has a long core pulling distance. This design scheme has a longer ejection stroke. Ejection force is large, top of plastic part is easily whitened and deformed. After mold opening direction is determined, parting surface of mold is a flat surface. It is necessary to pay attention to positioning accuracy of front and rear mold cores, so that front and rear molds are beautifully clamped at parting surface. Need to pay attention to mold processing, heat sink parts need to be processed directly in place by a high-speed machine, do not trim by hand.
Mold design adopts the first scheme design, and sliders are driven by oblique guide pillars. Glue feeding method is to feed glue at two points at mouth of box with one point gate. Plastic material is PP, plastic parts are easy to deform, and long sides of mouth are concave. Therefore, it is necessary to appropriately extend cooling time to reduce deformation.