Matched mold forming

In matched mold thermoforming (Fig. 10.9), matched sets of negative and positive molds are used to form the part from the softened sheet. Vacuum is generally applied through the negative cavity, as well. The result is excellent dimensional control, and the ability to form very complex shapes. This method is most often used in thermoforming of foams, due to their tendency to deform if not restrained. 

Top half of matched mold Heat-softened sheet Bottom half of matched mold 

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In matched-mold forming, a heated sheet is placed between a matched female and male mold parts. As the two mold halves close, they distort the sheet to their shape. The air between the mold halves is removed. The article walls are more uniform than for many of the thermoforming techniques. This technique is used for the production of foamed PS and foamed polyolefins food containers. 

In this case, a hot sheet is stretched over a mold or matched molds without the use of air or pressure. For example, in matched mold forming, the heated sheet is clamped over a female mold or draped over the mold force (male mold) (Figure 11.13). The two molds are then closed. The resulting part has excellent dimensional accuracy and good reproduction of the mold detail, including any lettering and grained surfaces. 

Why might you choose to use matched mold forming for a packaging application ... 

Various mechanical techniques have been developed for thermoforming that use neither air pressure nor vacuum. Typical of these is matched mold forming (Figure 2.41). A male mold is mounted on... 

FIGURE 2.41 Matched mold forming (a) heating (b) forming. 

Matched mold forming is a thermoforming process in which matched molds are used to assure a contained, defined part. Foamed PS egg cartons are a product example. See TJiermoforming. 

The types of thermoforming processes are vacuum forming, pressure forming, melt phase thermoforming, and matched mold forming. Examples of applications of thermoformed parts are ... 

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