Molds usually present the following similar basic components6 (Figure 10):
1. Mounting plate: Typically a heavy steel plate attached to the bottom of the mold frame that enables the mold to be attached to the machine;
2. Frame: Supports the mold cavity. It needs to be strong enough to support the mold, resist the torque applied for closure, and withstand repeated heating and cooling cycles. The frame, which can also be used as the attachment point for mounting plates, clamping, pry points and other components. The so called ‘’spider arrangement’’ represents multiple molds mounted in a single frame.
3. Posts: Connects frame to the mold. Posts are usually short to prevent distortion and cracking due to thermal variations.
4. Parting line flange: Critical part of mold design which is usually chosen based on the largest dimension of the part. Parting line flanges may be flat, tongue and groove and offset (stepped). Alignments pins along the parting line or a tongue and groove parting line can be useful to maintain alignment (Figure 11 A).
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Mold cavity: It may be as simple as two mold pieces with a flat parting line or more complex structures as multi-piece cavities molds (such as six or eight pieces mold) to allow complex parts to be removed.
6. Clamping or bolting mechanisms: There are many different clamping systems, such as over-center clamps, quick acting toggle bolts, spring-loaded bolts (at the parting line or through the spider), captive bolts and nuts, ‘C’clamps, and even vice grips.
7. Pry points: Provides lifting points where mold halves can be separated.
8. Vent pipe: Usually incorporated to allow equilibrium between the external atmosphere and the inside of the mold and to allow any unwanted emissions to escape and cooling air to enter the mold. Ideally, a vent should reach to the center of the part volume, and be located in an area that does not affect the final function of the part. Excess pressure can deform the mold and cause the part to