Tiantiantong terminal monitor bottom shell injection mold design
Time：2022-10-27 10:43:49 / Popularity： / Source：
It can be seen from Figure 1 that plastic part structure is a rectangular flat structure. Top surface of outer surface of plastic part is flat, there are only bones in the middle and part. On the back of plastic part, there are several full circles of bone positions and multiple column positions, and there are cross-inclined holes in the middle that collide with three holes on bottom surface. It is necessary to design slider core. Another inner hole on edge needs to be designed with an inner slider, and a buckle on the end face of shape needs to be designed with a rear mold slider.
Difficulty of mold design lies in the design of inner core-pulling slider of middle cross hole. Another difficulty in mold design is deformation of plastic parts. Characteristics of PBT are milky white translucent to opaque, and it is a crystalline thermoplastic polymer. It has excellent toughness and fatigue resistance, high impact strength, self-lubrication and wear resistance, small friction coefficient, small water absorption, good dimensional stability, so it can be used as engineering plastics, but its notch sensitivity is large. High melting point, up to 225 ℃, good heat resistance, good weather resistance, flame resistance, but slow burning. Excellent electrical properties, good arc resistance, but large volume resistance, high frequency dielectric loss. Resistant to hot water, alkalis, acids, and oils, but easily attacked by halogenated hydrocarbons and has poor hydrolysis resistance.
PBT plastic is easily deformed, and due to its hard texture, it is difficult to correct after deformation. Therefore, when designing mold, it is necessary to pay attention that mold temperature cannot be too high, it is necessary to design a sufficient cooling water circuit and cooling time is sufficient. Wall thickness of plastic part should be as uniform as possible. Plasticizing capacity of injection molding machine is sufficient and plasticizing is uniform. Thimble is adequate and designed in proper position.
In order to prevent deformation of plastic parts, mold flow analysis was carried out on mold. See Figure 5
MoldFlow software is a product of American MOLDFLOW company, which has been leading plastic molding CAE software market since it released the world's first plastic injection molding flow analysis software in 1976.
MoldFlow software is mainly used to provide users with design analysis solutions and manufacturing solutions. One of the most widely used design analysis solutions, its products include Moldflow Plastics Advisers (MPA), Moldflow Plastics Insight (MPI) and CAD Connectivity Tools.
MPI can simulate and analyze the entire injection molding process, including filling, packing, cooling, warpage, fiber orientation, structural stress and shrinkage, and gas-assisted molding analysis, etc., to identify possible defects in future products during design stage, and to improve success rate of a trial.
Mold flow analysis results of plastic parts are shown in Figure 5, and detailed mold flow analysis files are shown in attached file.
In order to prevent deformation of plastic parts, multiple water transport circuits were designed, and mold flow analysis was carried out.
Mold design cavity layout is 1 cavity, gate is a point gate, and glue is fed in three points. Mold base is standard mold base DCI3570. Note that thickness of panel is 50, and part of code mold is milled to 30. Here, milling edge cannot be ignored. If thickness exceeds 30, it is difficult for platen to clamp mold. A positioning pin is added to movable mold base to increase rigidity of B plate and square iron, that is, bottom plate. Mold base is designed with three levels of positioning, namely, positioning of guide post and guide sleeve, positioning of zero-degree positioning block on the edge of mold base, and positioning of positioning center at four corners of mold core. Die inserts into frame are positioned with a squeeze block in length direction.
Slider of rear mold is driven by inclined guide column, and inner slider adopts floating core pulling of mold plate, as shown in Figure 4. Sequential parting mechanism adopts button machine to control movement of mold opening. Ejection of plastic parts adopts thimble, flat thimble and cylinder ejection.
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