Audio front shell product is shown in Figure 1. Maximum size of product is 129.54 mm * 38.00mm * 35.94 mm, average thickness of plastic part is 1.80 mm, material of plastic part is ABS, shrinkage rate is 1.004, and weight of plastic part is 16.56 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 Picture of Front Speaker
Structure of plastic part is a heterosexual shell, design of plastic part and 3D mold is shown in attached 3D drawing. It can be seen from Figure 1 that two sides of plastic part need to be designed with large slider cores. There is an inverted buckle at the end of plastic part, which requires design of a small slider for front mold.
Production batch of plastic parts is huge. Because both sides need to be designed with large slide cores, mold design cavity ranks 1 cavity is the best. Mold base is standard mold base FC13035. Choice to simplify fine nozzle mold base is mainly to save 4 guide posts and increase space at the edge of mold in order to facilitate design of a wider slider. Glue feeding method of plastic parts is to transfer glue from submerged nozzle to submerged gate, making a submersible gate, submerged column position, thimble is ejected before trimming.
Glue area of sliders on both sides is large, and lateral force is large. Therefore, two large sliders are designed with backhoes. Shovel is a mosaic shovel, which is convenient for extending movable mold as a backhoe. Two large sliding blocks are driven by oblique guide posts. Since top surface of slider is a complex curved surface, in order to facilitate processing, slider insert is selected to be inserted from end surface to simplify processing.

 

When designing mold, slider with a curved top surface cannot be designed as a whole. If it is designed as a whole, connection between curved surface and slider seat requires EDM, which is time-consuming and laborious, it is not easy to adjust when flying mold. The other front mold slider is driven by bending pins. In order to facilitate processing and venting during injection molding, back mold has a large insert in the middle part, see 3D diagram. For shape of front mold core, pay attention to strength of mold core, and choose pre-hardened mold steel NAK80.
Plastic part is ejected by a thimble. After thimble is assembled, it needs to be twisted manually to detect. If it can be twisted easily, gap is reasonable. Otherwise, gap is too small and it is easy to burn to death during ejection process, it is difficult to exhaust. Ejection process needs to be stable to prevent plastic parts from deforming, and thimble plate needs to be designed with a center torsion guide. In long-life molds, heat-resistant thimble is required, and surface is plated with titanium to increase wear life.
Cooling of mold is that front and rear molds are all cooled by straight-through water. Direct water flow is fast and cooling efficiency is high.
There is a problem with code model, which is often overlooked. For small nozzle molds, panel is often very thick, and it needs to be milled thin at the position of code mold, leaving a thickness of 25-30 to ensure that code mold can be pressed tightly.

 

 

 

 

Figure 2 Die diagram of the front shell of speaker