A thermoforming trim press has one or more connecting arms for driving a movable platen, each arm having a pivotal connection between two adjacent sections of each connecting arm which is normally locked during normal press operation whereby the movable platen is able to move further back from a normal retracted position to increase the available clearance when changing or maintaining tools mounted on the movable platen. The pivoting ability of the connecting arm sections also simplifies adjusting the stroke of the press. A counterweight may be driven by the crank pins to match the press stroke adjustments and to thereby correspond the movement of the counterweight to the movement of the movable platen.