Case Study: Pneumatic Chuck Jaws

Process: Metal Additive Manufacturing (AM)

Material: 17-4 PH Stainless Steel

Density: 99.5% of Theoretical

Ultimate Tensile Strength: 1250 MPa minimum

Hardness: 38 HRC

Download the PDF

End Use and Function

This pneumatic chuck jaws set is used for work-holding the outer diameter (OD) during precision turning on a CNC lathe. Traditionally, the jaws were machined from mild steel. Although inexpensive and easy to manufacture, the traditional chuck jaws were bulky and required high clamping force to overcome centrifugal force during start up and shutdown. In addition to the three OD clamping jaws, the complete set includes a Z-axis stop.

Fabrication

The parts are made using material jetting (MJT) and the printing process allows the inner-lattice structure to be formed without having to de-powder, eliminating the risk of any powder entrapment in difficult to access areas. Vents and drains are designed into the printed jaws to allow the mold wax to flow out during the de-molding process. The robust part design requires no special sintering furniture. The 17-4 PH stainless steel parts are sintered at 1350 °C in a vacuum furnace to a 99.5% relative density with a tensile strength of 1250 MPa and a hardness of 38 HRC.

Results

Compared with traditional work-holding jaws, these light-weight jaws are 1,800 g lighter, offering an 84% reduction in rotating mass and a fraction of the centrifugal force that the pneumatic chuck must overcome at full rotational speed. The lower centrifugal force requires a clamping pressure roughly one-third of what a traditional chuck would require, reducing out of round conditions on thin-walled parts. Additionally, design and build time was reduced from 6 weeks to 2 weeks. The MJT printing process generates little waste, and the wax used to form the mold is recovered and can be re-used for the next build.