There are several variations in the thermoforming methods used to mold a plastic into a desired shape. These include pressure (air), vacuum, and occasionally, just the force of two individual surfaces are used to crush plastic being thermoformed. The types of thermoforming molds used include; cast aluminum molds, machined aluminum molds and wood pattern molds.
Products of the thermoforming process of plastics, are divided into two groups, light gauge and heavy gauge, roughly along the lines of the equipment style that are generally utilized in making the thermoformed product. Light-gauge thermoplastic items are typically used in packaging, but some are also products in themselves. Their gauge, is typically 0.003 to 0.100. The products are usually manufactured on roll-fed in-line thermoformers.
Heavy-gauge items usually are products, but some packaging applications do appear in this group as well. Their gauge is typically 0.100 to 0.500 and thicker. The heavy gauge products are typically manufactured on cut-sheet or sheet-fed equipment such as a rotary thermoformer, a single-station thermoformer, and a shuttle thermoformer.
The thermoforming processes used today are straight vacuum forming, drape forming, plug-assist forming, pressure-bubble plug-assist vacuum forming, vacuum snap-back forming, and mechanical forming. There are limitations that still persist in the use of thermoforming in manufacture of plastics, these include; problems in depth-of-draw applications, lack of uniform wall thickness, whenever a thermoformed plastic is used as product for example as enclosures for electronic components, the product must be CNC (computer numerically controlled) trimmed to height or size, the holes must be drilled, and support or standoff blocks must be located. These processes are time consuming and generally costly, hence thermoforming processes are usually used in low volume applications.
