In compression molding, a preshaped charge of material, a premeajured volume of powder, or a viscous mixture of liquid resrn and filler material IS placed directly into a heated mold cavity. Forming is done under pressure from a plug or from the upper half of the die (Fig. 18.12). Compression molding results in the formation of flash, which is subsequently re¬moved by trimming or by other means.
FIGURE 18.12 Types of compression molding, a process similar to forging:
(a) positive, (b) semipositive, and (c) flash. The flash in part (c) has to be tnmrned off. (d) Die design for making a compression-molded pari with undercuts.