The simplest and most reliable mould design is the two-plate tool.This is because it normally has the fewest number of moving parts and is more straight forward to manufacture and run in production. Because of its simpler construction it is usually cheaper to manufacture than more complex designs.
Given the simplicity of its design and manufacture, mould design engineers should make sure that all possibilities of using a two-plate design have been exhausted before other more complex designs are considered. This means that the component should be examined carefully to see whether any undercut features could be designed out of the part.
Screw threads are a prime example of this point. Threads normally require split tools, collapsible cores or more complex automatic unscrewing devices, but sometimes they can be jumped out of the cavity.
A typical two-plate mould tool is shown in Figure 9.1. Figure 9.2 shows a typical full (but deliberately simplified) general arrangement (GA) drawing of a two-plate mould tool. In practice, the general arrangement drawing would be considerably more detailed than this. However, this simplified version illustrates more clearly, the basic construction of a typical two-plate mould tool.
Walsh's Plastic consulting. 