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Thermoforming Processes
Thermoforming is a means of shaping thermoplastic sheet to
conform to the contours of a mold through the use of heat and pressure, either
positive or vacuum. In thermoforming. dry sheet stock is heated to a
predetermined temperature at which the plastic softens but is below its melt
temperature stretched to cover the contours of a mold with the use of vacuum and
cooled to a temperature at which the thermoplastic becomes rigid. Thus
retaining the shape of the mold. The formed part can then be trimmed to
eliminate edges, decorated and/or fabricated into an end-use article. Each step
of the forming process is vital to the quality of the finished part. Sheet
quality along with the heating. forming. and cooling parameters has to be
monitored and controlled in order to obtain quality parts. Quality parts require
uniform wall thickness, desired surface appearance, both in color and color
consistency, and acceptable physical properties for the end use. Thermoforming
can accommodate a wide range of sheet thicknesses from thin-gauge sheet used to
form packaging containers to heavy-gauge sheet used to make boat hulls and
recreational vehicle tops.
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