Posters

Hybrid manufacturing of light metals

Justin West, Tony Schmitz

Department of Mechanical Engineering and Engineering Sciences UNC-Charlotte null Department of Mechanical Engineering and Engineering Sciences UNC-Charlotte

Wire arc additive manufacturing (WAAM) uses an electric arc to locally melt and fuse wire to build parts layer by layer. The benefits are a high deposition rate, dense final structures, and compatibility with light metals such as aluminum and magnesium. In gas metal arc welding (GMAW), wire is fed continuously into the arc where it is melted to form a bead. WAAM parts typically need to be finish machined to achieve desired final part geometry and surface finish. This creates a challenge when moving from an additive machine to traditional machining centre, as it is difficult to align machine axes without a reference feature.  One solution to this problem is hybrid manufacturing, where the additive process and machining centre are coupled. The work coordinate systems of the welding torch and subtractive machining spindle are set from the same reference, and the part is built and machined on the same fixture. This allows for a reduction in the material used, setup time, and makes it easier to achieve desired final part geometry. For this setup, an off the shelf gas metal arc welder is mounted adjacent to the machine spindle and is triggered using the machine controller. A fixture plate was designed to isolate the machine from the thermal and current input. To develop an understanding of the process, a 5356-aluminum alloy was chosen as a less expensive and better-understood alternative to magnesium. Once the process parameters and relationships are better understood, testing with magnesium alloys will begin.

Additive manufacturing of internal features for manipulation of structural dynamics

Emma D. Betters¹, Justin West¹, Mark Noakes², Andrzej Nycz², Scott Smith², Tony L. Schmitz¹

¹Department of Mechanical Engineering and Engineering Science

UNC-Charlotte, Charlotte, NC

²Manufacturing Demonstration Facility Oak Ridge National Laboratory, Oak Ridge, TN

In machining processes, the machine structure, spindle, holder, tool, and workpiece collectively compose a dynamic system that defines the ideal cutting parameters when machining. In an effort to improve the stiffness of a machining center or other machine structure, the base can be designed to increase the stiffness and damping. However, traditional casting processes for machine bases are geometrically limited, labor intensive, and expensive to produce. An alternative approach is to use an additive manufacturing process to form a machine base with the design freedom to enable arbitrary internal features. These features can be used to shift the structural dynamics of the system to a desired natural frequency or to minimize the dynamic response at a given frequency, for example.A pair of demonstration components were designed and produced to showcase the ability of the wire arc additive manufacturing (WAAM) process to print internal features which can be designed to alter the structure’s dynamics (e.g., by altering the natural frequency or increasing the dynamics stiffness). The first component was a simple open channel attached to a base. The second component was identical, but contained a dynamic absorber, designed to minimize the displacement response at the natural frequency of the open design, in the open internal cavity. The design and finite element analysis validation of the dynamic absorber, the additive and subtractive manufacturing processes, and a comparison of the frequency responses for the final components have been completed.

Influence of SLM Processing Parameters on Mechanical Properties of Tungsten-Heavy Alloys

Lehigh  University