One machine, two processes

Additive and subtractive manufacturing may be conceptual opposites, but a new partnership aims to show that the two can make a good team.

Two of the partners are New York organizations: the Rochester Institute of Technology (RIT) and Elmira-based Hardinge Inc. RIT researchers are incorporating additive-manufacturing capabilities into Hardinge’s Bridgeport GX 250 5-axis vertical machining center. The goal is to create a hybrid manufacturing system capable of producing more accurate parts at a lower cost than conventional manufacturing methods.

Researchers are adding components that will allow directed energy deposition (DED) within the machining center. DED creates parts using a focused heat source, such as a high-powered laser. This simultaneously melts a substrate and powder feedstock (typically metal powders, but also ceramics, polymers and metal-matrix composites) into the substrate melt pool.

A Bridgeport GX 250 5-axis vertical machining center finish-machines a complex turbine blade. Image courtesy Hardinge.

“There is melting and resolidification, just like you have in welding,” explained Ronald Aman, project leader and assistant professor of industrial and systems engineering at RIT’s Kate Gleason College of Engineering. The small melt pool solidifies in less than a second, he added.

With each pass of the DED head, a single layer of solid material is produced. Layer upon layer build up, eventually resulting in a 3D part.

Work on 3D metal printing is more than a decade old, but reliable part building can still only be done with one material at a time, according to Aman, who hopes that will soon change.

His team is equipping the GX 250 with multiple powder feeders. These can blow a number of different metal and ceramic powders into the DED melt pool. Besides opening the door to a variety of material combinations, Aman said this configuration will make it possible for users to smoothly transition from one material to another while manufacturing parts. As a result, there will be no need for abrupt material-composition changes, thereby eliminating common failure points on parts made of materials with vastly different mechanical or thermal properties.