Terminal movement support product is shown in Figure 1. Maximum size of product is 143.34 mm * 115.00mm * 13.30 mm, average thickness of plastic part is 2.00 mm, material of plastic part is ABS, shrinkage rate is 1.005, weight of plastic part is 26.58 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, etc.

 

 

Figure 1 Product diagram of terminal movement bracket
Structure of plastic part is a rectangular hollow flat shell, and structure of plastic part is shown in attached 3D drawing. Movement bracket, as name implies, is to provide fixing and positioning components for PCB board in instrumentation. Technical requirement of movement support is that plastic part is flat, free of deformation and warpage, stable in size after long-term use. Another technical requirement of movement support is high dimensional accuracy, installation position is generally marked with dimensional and geometric tolerances. Characteristic of mold design of movement bracket is that mold structure is simple and there is no complicated mold structure. A well-designed exhaust is required to avoid deformation of plastic parts.
Characteristic of movement bracket and mold design is that there is little difference in packing force of front and back molds on the front and back of plastic part. An accurate judgment needs to be made during mold design. This judgment is usually called mold opening direction analysis. Mold opening direction analysis is basis of mold parting surface design. If mold opening direction analysis is wrong, mold is easy to stick to front mold, and poor mold design will occur.
Based on judgment of mold opening direction, design of parting surface is carried out. Parting surface of movement support is not a flat surface, there are many steps and scratches in some parts. Parting surface design needs to consider tool processing, design pillow position as much as possible, and do not design rubbing position.

 

A key point in 3D parting is design of draft angle. Movement bracket is a flat plastic part, with more bones and shallower bones. Any bone position with a depth of more than 1mm must be designed with a draft angle. The shallower depth, the larger draft angle can be selected. Specifically, difference between size and end of plastic part's bone position is above 0.1.
Mold design cavity rank is 1 cavity, mold base is standard mold base CI3050, gating system is designed as a latent gate, and mold is injected after 1 point. For flat plastic parts, plastic process is longer, injection pressure is large, and clamping force required by mold is large. Therefore, mold parting surface pressure is required to be large, ideal state is to adopt a hard mold design to increase design life of mold. This set of molds adopts NAK80, a pre-hardened steel with higher hardness. Exhaust of front and rear mold cores on parting surface cannot be ignored, otherwise injection pressure will increase and cloaks will easily appear.
Both front and back molds are designed with cooling and water transportation circuits, and all adopt direct water transportation design to improve cooling efficiency. Ejector of plastic part is ejected by a thimble, and all thimble holes are cut out by wire cutting.

 

 

 

 

 

Figure 2 Mould diagram of terminal movement bracket