Abstract: A twin sheet thermoformer apparatus using hydraulic cylinders to draw the upper and lower platens together for uniform seam forming of the part. A flow divider insures uniform travel of each hydraulic cylinder. An adjustment mechanism enables simultaneous adjustment of the position of four locking shafts on one platen coupled to form locking shafts on the other platen preparatory to operation of the hydraulic cylinders. The adjustment mechanism includes nut members each threaded onto a locking shaft with a recirculating chain engaged with a sprocket on each nut member. Driving the chain enables simultaneous adjustment of each shaft to allow the platen positions to be quickly and accurately adjusted. An encoder generates signals corresponding to the lower platen travel caused by operation of the hydraulic cylinders, which are transmitted to the lower platen drive servo motor to drive the lower platen correspondingly.