Thin-and Thick-Gauge Thermoforming

A film/sheet thickness of less than 1.5 mm (0.060 inches or 60 mils) is referred to as thin-gauge thermoforming and is usually used in rigid or disposable packaging applications. At this thickness level, the polyethylene may be transferred to the molding cavity from a roll or pre-cut sheet. Thicker gauges above 1.5 mm (up to about 0.250 inches) are handled as sheets which are pre-cut to fit a particular molding application. 

Three different methods (or a combination of methods) are used to form the polyethylene into the mold cavity  

The vacuum is formed between the polyethylene sheet and the mold cavity so that the softened polyethylene is forced against the walls of the cavity to the designed configuration. 

In this method, a vacuum is applied to one-half of the cavity between the polyethylene sheet and the lower half of the mold, while air-pressure is simultaneously applied to the upper part of the cavity between the polyethylene sheet and the cavity wall. 

This method involves forcing the polyethylene sheet into the cavity by using a male/female mold design in which the male portion of the mold pushes the polyethylene into the female-shaped cavity. 

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The thermoforming mold is usually single-surfaced. Aluminum is the preferred material for longer production runs for both thin- and thick-gauge thermoformers. The mold serves several purposes and has several requirements. 

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