A piston (10) containing a cavity (16) is manufactured by forming a box (20; 50; 70; 80). The interior of the box defines the cavity (16). The box ms mounted in a die cavity (26) and the piston is cast around the box. The box is provided with projections (22c; 24c; 52; 58; 73) which enter recesses in the wall of the die cavity and support the box. After removing the piston from the die cavity, the projections are machined off.
Variable displacement pistons are produced wherein hollow piston bodies are integrally formed with associated actuator arms to ensure proper alignment of the bodies and rods. The process utilizes a two-axis press to first form a pair of actuator arms by working a blank of metallic material along a first axis between opposing members of a die assembly. With the die assembly still closed after formation of the actuator arms, a pair of hollow piston bodies are formed by extruding the remainder of the blank of metallic material along a second axis. The hollow piston bodies are axially aligned and integrally formed with respective ones of the actuator arms. A piston head is welded to the end of each hollow piston body which is then machined. By separating the actuator arms from one another, a pair of variable displacement compressor pistons having hollow piston bodies axially aligned and integrally formed with respective actuator arms are thus formed.
