Radio bracket product is shown in Figure 1. Maximum external dimension of product is 297.13 mm * 114.59 mm * 66.69 mm, average thickness of plastic part is 2.50 mm, plastic part material is ABS+PC, shrinkage rate is 1.0065, and plastic part weight is 108.10 grams. Technical requirements for plastic parts are that there shall be no defects such as peaks, underfilling, flow lines, pores, warpage deformation, silver lines, cold materials, and spray lines.

 

Figure 1 Product Diagram of Radio Stand
Radio stand product is a complex product, shape is divided into 3 parts, left and right parts are nearly symmetrical, middle is connecting section. For complex plastic parts, first determine mold opening direction, that is, selection of movable and fixed molds, then design parting surface and determine three elements of mold design. It is not difficult to determine opening direction of plastic parts of this set of molds. Top surfaces of the two ends of plastic parts have a sunken shape, which has a certain tightening force for mold core, but four sides of sunken shape have a large slope and are easy to demould. There are multiple bone positions on the back of both ends of plastic part, and tightening force on mold core is relatively large. In middle part, top surface is smooth, wrapping force is small, back has multiple bones and complex structural elements, which has a large wrapping force on mold core. Therefore, through above comprehensive analysis, side with more bones is designed in movable mold.
After mold opening direction is determined, parting surface can be determined. Plastic parts are complex, edges are undulating, and parting surface is complex. It is necessary to use 3D software to analyze segment by segment, reasonably determine pillow position, penetration, and use a set of relative triangles to mark parting line. For a complex parting surface with large fluctuations, it is necessary to analyze function of product in this part when selecting, and combine product tolerance to determine appropriate demoulding slope, reduce glue and draft, so as to determine parting surface. On the premise of ensuring product function and tolerance, choose a flat parting surface as much as possible, which is conducive to mold processing and assembly. Marking of parting surface is shown in Figure 2.
Size of plastic parts is large, mold cavity ranking is 1 cavity, and a single YUDO hot nozzle feeds glue. In order to prevent deformation of plastic parts, use of mold flow analysis technology can simulate and analyze the entire injection molding process before mold is processed, accurately predict filling, pressure holding, and cooling of melt, as well as stress distribution, molecular and fiber orientation distribution in product, shrinkage and warpage deformation of product, so that designer can find problems as soon as possible, modify design of plastic parts and molds in time, instead of waiting for mold to be repaired after mold is repaired.
Moldflow analysis can be successfully applied to three different groups of processes, namely plastic product design, injection mold design, and injection molding. For large molds, mold flow analysis is particularly important. If design of large-scale mold casting system is unreasonable, it will cause great losses and waste of plastic raw materials. For high-speed injection of thin-walled injection parts, mold flow analysis will also be of great help.
Mold flow analysis can output important design data, such as pressure distribution, temperature, shear rate, shear stress, speed, etc., designers can obtain from CAE such as filling mode, location of weld lines and air pockets, injection pressure and clamping force Information such as size, fiber orientation, plastic part deformation, cooling time, final shape, etc. As a design tool, CAE can assist mold designer to optimize runner system and mold structure, assist product designer to improve product shape from perspective of injection molding process, select plastic with the best molding performance, help injection molding engineer to set the most reasonable process conditions.
Mold base is CI3550-A80-B100-C120, guide post and guide sleeve imitate HASCO standard, and guide post is inverted, which is convenient for manipulator operation. Mold core is made of European typical steel 1.2344 and heat treated at 48~52HRC. In order to facilitate operation of manipulator, mold has a shallow fine frame, and a balance block is added to edge of A plate, as shown in Figure 6 and Figure 7.
Movable and fixed molds of mold cooling system all adopt straight-through water transportation, and a heat insulation board is designed in fixed molds. Ejection of plastic parts is ejected by ejector pins. Ejection method is a typical European strong-pulling and strong-pulling method. There is no spring on return needle, and injection-molding machine is used to force strong-pulling way to shorten injection cycle and reduce deformation of thimble plate.

 

Figure 2 Schematic diagram of parting surface of radio bracket

 

 

 

 

 

Figure 3 Process diagram of mold flow analysis

 

Figure 4 3D drawing of back mold

 

Figure 5 3d drawing of front mold

 

Figure 6 Fixed mold plan

 

Figure 7 2D section view