Deformation machining combines two techniques

Courtesy of All photos courtesy of UNC Charlotte

Figure 1. Deformation machining bending mode: thin-wall machining (top), followed by single-point incremental forming (middle) to create an inclined wall (bottom).

Deformation machining is a new hybrid process that combines two manufacturing techniques: thin-part machining and single-point incremental forming (SPIF). Researchers at the University of North Carolina at Charlotte (including the author), Northwestern University and Clemson University developed the process, which allows use of a 3-axis CNC machine to create part geometries that usually require a 5-axis machine. This technique could possibly reduce the machining time and cost of producing impellers, which are typically milled on a 5-axis machine.

Thin-part machining uses a special milling tool and machining strategy to create monolithic components with walls and floors that can be as thin as sheet metal (see the September 2009 “Machine Technology” column). Monolithic machined parts have replaced sheet metal assemblies in numerous aerospace applications.

SPIF is a forming operation originally developed to manufacture sheet metal components without the expense of creating a die. A tool that looks like a ballnose endmill without teeth contacts sheet metal held in a frame at a single point. The tool follows a path that incrementally deforms the workpiece into the desired geometry.

Figure 2. This array of thin fins produced via deformation machining weighs less than a similar array made with 5-axis machining because the acute angle at the root of the wall does not have to allow for tool clearance.

Figure 1 summarizes deformation machining. The thin-wall machining progresses in layers from top to bottom and a wall is machined to its finished dimension at each step. In this way, wall stiffness is maintained during machining.