PROCESS : Sheets of pre-extruded rigid plastic are heated horizontally and sucked down into hollow one-piece tools. After the hot plastic solidifies again, its shape conforms to that of the mold. Trimming is usually necessary to put the part in final form. Vacuum forming is done at atmospheric pressure (14.2 psi). A variation of this process, pressure forming, incorporates the use of a pressure box built around the tool which increases the pressures far beyond atmospheric. Greater surface definition in parts can thus be achieved.
RAW MATERIALS : Most thermoplastics are usable. Must be in sheet form.
TOOLING : Generally, machined aluminum is used, although poured composites and even wood can be used for short runs.
COST : Tooling costs are generally low and piece prices are strictly dependent upon the speed of the machinery.
ADVANTAGES : Vacuum forming equipment generally available in most geographical areas. Costs are generally low.
DISADVANTAGES : Poor surface definition. Thin spots in corners. Deep draw limitations.
EXAMPLES : Covers, displays, blister packaging, trays, drinking cups & food packaging.