Design of Injection Mould for Green Single Door Refrigerator Drawer and U-shaped door frame cover
Time：2020-11-10 16:47:14 / Popularity： / Source：
Design of Injection Mould for Green Single Door Refrigerator Drawer
Green single-door refrigerator drawer product diagram is shown in Figure 1. Maximum dimensions of product are 492.40 mm * 284.95 mm * 194.42 mm, average thickness of plastic part is 2.50 mm, plastic part material is PP+%25K, shrinkage rate is 1.009, weight of plastic part is 885 grams. Technical requirements for plastic parts are that there must be no defects such as peaks, insufficient injection molding, flow lines, pores, warpage deformation, silver streaks, cold materials, jet lines, etc.
Figure 1 Product Picture of Green Single Door Refrigerator Drawer
This product is designed for drawers of an Italian brand refrigerator. It can be seen from Figure 1 that plastic part is a box shape with one side open, size of plastic part is large, and production batch of plastic part is also large. Mold is required to have good long-term service performance and mold life is 300,000 mold times.According to size of plastic part and specifications of customer's injection molding machine, mold design cavity is layout as 1 cavity; size of plastic part is larger, and molten plastic process is longer, so gating system is designed as a hot runner mold. Gate position is on bottom surface of refrigerator drawer, and two point gates are filled with material. Hot runner system adopts DME brand.
Because it is a hot runner mold, mold base is a non-standard mold base CI5575; two inclined positioning blocks 10 are designed on long side of mold base to prevent lateral deviation caused by injection pressure. Two non-standard positioning blocks 3 are designed on both sides of top and bottom to facilitate accurate mold clamping. Mold is a large-scale mold, cavity is left in its original form, and cavity is directly processed on the A plate. At this time, material of A plate needs to be made of die steel 1.2768.
In order to prevent plastic parts from deforming and shorten injection cycle of refrigerator drawer mold, sufficient cooling water circuits are designed for front and rear molds. Water transported by front mold is straight-through water, which is evenly distributed around cavity. Back mold is a pond. Adequate cooling system design can ensure that plastic parts are not deformed and injection molding can proceed normally.
Ejection of plastic parts depends on push block 4, push block 9 and ejector pin. Push block 4 is pushed out with push rod 6 and guided by guide bush 5. Push rod 6 is directly fixed on thimble plate. Ejection mechanism is a European mold structure with strong tension and strong ejection. No spring is set on return pin. Tap M24 at corresponding position of 5 K.O holes on ejector plate, which is convenient for connecting ejector rod of injection molding machine. Thimble plate is designed with a travel switch 13 to confirm return.
Figure 2 Drawing of drawer mold of green single door refrigerator
Figure 3 3D drawing of green single door refrigerator drawer mold
Design points of injection mold for U-shaped door frame cover
Product picture of CU door frame cover is shown in Figure 1. Maximum size of product is 268.88 mm * 130.13 mm * 30.99 mm, average thickness of plastic part is 2.20 mm, plastic part material is ABS NH30, shrinkage rate is 1.0045, weight of plastic part is 10.73 grams. Technical requirements for plastic parts are that there must be no defects such as peaks, insufficient injection molding, flow lines, pores, warpage deformation, silver streaks, cold materials, jet lines, etc.
Figure 1 U-shaped door frame cover product picture
It can be seen from Figure 1 that plastic part is shaped like a thin sheet bent into a U-shape, and there are 7 undercut positions along edge. It is necessary to design a lifter or slider core. Difficulty of mold design is that size of plastic part is large and shape is non-closed. This kind of plastic parts has a long plastic filling process and is difficult to fill. Easy to deform when ejected.
Mold alignment takes into account tilting characteristics of plastic parts, and uses symmetrical alignment to balance forces. Considering strength of mold, front and rear mold cores are equally divided into two pieces. Processing of parting surface is very critical. For inclined parting surface, high-speed CNC processing is required to avoid defects caused by manual trimming.
Due to special shape of plastic part, plastic part occupies a small space on both sides of mold, and clamping force is not balanced during injection molding. In order to solve this problem, two balance weights were designed on the top and bottom side of mold. A balance weight is designed on the left and right sides. Balance weight needs to be heat-treated, quenched and ground flat, fixed on the edge of movable and fixed mold embryo with flat screws.
According to long length of plastic part, gate is designed in the center of plastic part. Gate is a side gate.
7 buckles on the edge of plastic part are all designed with small sliders. All slides are driven by T-slots. Under normal circumstances, use inclined guide posts to drive slider as much as possible. Sometimes, when space is limited, a T-slot drive can also be designed to replace inclined guide post.
In order to prevent plastic parts from deforming, front and back molds of mold need to be designed for cooling and water transport. Distance between cooling water and plastic parts is 14.5, evenly arranged to reduce deformation of plastic parts.
Ejector of plastic part is ejected by a thimble, and thimble plate is guided by center tors.
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