The mold includes a forming plate, clamping plate, and a male plug. The molded part's outside contour conforms to the forming plate, but its opening is larger. To provide a sheet's thickness clearance between the male and female mold parts, the slightly tapered male plug is smaller than the forming plate's inside dimension. The mold can be set up in an air cylinder press or in an arbor or drill press for small parts. The male plug is forced through the clamping and forming rings to a predetermined depth.
Vacuum snap-back forming employs a male plug attached to an air cylinder's ram.
The plug is lowered into the vacuum-formed bubble. Drawing vacuum on a hot sheet forms a bubble. A male plug is positioned inside the bubble. This method enables production of irregular shapes, with the forming plate's cutout and the male plug's shape controlling the contour. Don't just cool the surface - the interior must also cool.