PCB guide plate product is shown in Figure 1. Maximum size of product is 254.84 mm * 217.70 mm * 57.00 mm, average thickness of plastic part is 2.50 mm, material of plastic part is ABS, shrinkage rate is 1.005, and weight of plastic part is 219.60 grams. Technical requirements of plastic parts are that there must be no defects such as peaks, dissatisfaction with injection molding, flow lines, pores, warpage deformation, silver streaks, cold materials, jet lines, etc.

 

 

It can be seen from Figure 1 that plastic structure is a flat shell. There are various raised bone positions on four sides. Except for two undercuts on one side, which need to be designed with a slider core, shapes of various bone positions on the other three sides can all be solved by S/O and KISS-OFF of front and back molds, pillow position. This article is accompanied by 3D diagrams. Readers can practice 3D parting and making parting surface connections according to guidelines of this article.
Insertion SHUT OFF/(S/O), knock-through (KISS-OFF) and pillow position are three very important concepts in injection molds. In design of mold parting surface, we often encounter how to determine use of penetration or bumping and pillow position. In Taiwan Province, penetrating is also called rubbing, and bumping is also called rubbing. As name suggests, rubbing and bumping often appear in shape of plastic parts with holes, holes, grooves, or sharp changes in parting surface. Pillows mostly appear at gaps or steps at edges of plastic parts, where parting surface fluctuates sharply.
Due to diversity of product structures, in design of plastic molds, penetration position and pillow position are frequently involved structures. For complex molds, there may be multiple penetrations, bumps and pillows, and there may also be interlaced and compound penetrations, bumps and pillows. Reasonable design of penetration, bumping and pillow position are direct factors affecting life of mold. Penetration is also one of factors prone to flash.
The most important principle of parting surface design is: preferentially choose bumping, use pillow position as much as possible, and use penetration with caution. For rubbing position, due to large friction, penetration surface usually needs to be designed with a slope of 3° or more. When height of penetration surface is small, take a large slope, and when height of penetration surface is large, take a small slope; when insertion depth is large or structure is easy to damage, it is usually made into inserts to facilitate mold maintenance and replacement. In terms of choice of steel, choose a steel with higher hardness at insertion and pillow position, or heat treatment of mold core to make a hard mold, which can significantly improve life of mold.

 

Figure 1 PCB guide plate product picture

Mold design cavity layout is 1 cavity, mold base is CI4055, and gating system is a single-point needle valve hot runner injection. Design positioning pins between panel and A plate to increase rigidity of mold. Zero-degree positioning blocks are designed on the left and right sides of mold base to increase accuracy of mold clamping.
Size of plastic part is large, front and rear mold cores are 260 mm * 340 mm, front and rear mold cores are large. For such a large mold core, it is difficult to match frame. Therefore, front and rear mold cores are positioned at reference angle and squeezing block is squeezed tightly. Four corners of front and rear mold cores are designed with tiger mouth positioning to ensure a good position after mold closing.

 

Plastic parts are ejected with a thimble and 4 inclined ejectors. Both front and rear molds are designed for pond cooling.

 

 

 

Figure 2 PCB guide plate mold diagram