Abstract: Preheated plastic sheets are squared and flattened to be engageable by clamping fingers of clamps on a clamping frame by an array of paddles having vertical and horizontal portions moved to engage any upturned or skewed sheet edges to flatten and square the same as said paddles are simultaneously moved longitudinally and vertically by respective actuators.

Abstract: A forming station for a thermoformer in which the lower platen is lowered and moved laterally on linear bearings on the machine frame after two sheets are formed in side by side mold-plug assist tool sets so as to align the respective molds and formed sheets. The formed sheets are squeezed together with flanges on the formed sheets thereby fused together by a draw mechanism including a series of hydraulic cylinders which are connected to coupled elements carried by the upper and lower platens so as create the squeezing movement when the cylinders are pressurized. A precision control is exercised over the operation of each of the cylinders using a position sensing device associated with each cylinder to insure equal movement of the output member of each cylinder. The lower platen vertical drive is activated in correspondence with the travel produced by the hydraulic cylinders to reduce the load on a brake holding the upper platen stationary.

Abstract: A closed loop control of a heater bank used to preheat sheet plastic in preparation for thermoforming said sheet. The heater bank has zones of the heater bank in which the heaters are variably energized to produce greater heating in some areas of the sheet. A global percent increase in energization of all of the heaters is produced in correspondence to the sensed temperature of a location on the sheet to better control and speed the preheating process.