Hybrid additive manufacturing for tooling applications

Abstract

The requirements for tooling manufacturing are dimensional accuracy, surface performance, hardness, wear resistance, fatigue strength, repairability and cost. In this research, a methodology for hybrid additive manufacturing, Direct Energy Deposition (DED) and milling process was tested on geometries and materials relevant to the tooling industry. The first stage consisted of the powder feeder characterization. Next, a full design of experiments evaluating laser power, feed, and mass flow with three levels each and their impact on height and width. The third stage was to evaluate the internal structure of single lines with three sets of parameters, evaluating height, width, melting pool height and porosity. Afterwards, five different layer thicknesses were tested on thin walls of six layers each. The results show the effect of layer thickness on the height of the wall, melting pool height and wall’s porosity. Finally, two different scanning strategies were tested to evaluate cubic geometries. The scanning strategies were zigzag 90° and zigzag 360°. Cubic geometries created on DED were machined to create truncated pyramids with a 3° angle by milling. Three different feed per tooth were tested each 2.5 mm of the truncated to evaluate the surface roughness. Results showed a parabolic behavior and the best value for average surface roughness near 0.4 micrometers. After the analysis, the hardness of the samples was characterized by a hardness test. The results showed an average hardness between 30 and 50 HRC which is between the operational hardness values for the tooling industry.