Process
Vacuum forming is usually restricted to forming plastic parts that are rather shallow in depth. Thin sheets are formed into rigid cavities for unit doses of pharmaceuticals and for loose objects that are carded or presented as point of purchase items. Thick sheet is formed into permanent objects such as turnpike signs and protective covers. Normally, draft angles must be present in the design on the mold (a recommended minimum of 3°). Otherwise, release of the formed plastic and the mold is difficult.
Relatively deep parts can be formed if the formable sheet is mechanically or pneumatically stretched prior to bringing it into contact with the mold surface and applying vacuum.
Suitable materials for use in vacuum forming are conventionally thermoplastics. The most common and easiest to use thermoplastic is high impact polystyrene sheeting (HIPS). This is molded around a wood, structural foam or cast or machined aluminum mold, and can form to almost any shape. Vacuum forming is also appropriate for transparent materials such as acrylic, which are widely used in applications for aerospace such as passenger cabin window canopies for military fixed wing aircraft and compartments for rotary wing aircraft.
Read more about this topic: Vacuum Forming
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