Slicer and Process Improvements for Open­source GMAW ­based Metal 3­D Printing

Low­cost gas metal arc welding (GMAW)­based 3­D printing has proven effective at additive manufacturing steel and aluminum parts. Early success, however, was based on hand­writing G­code, which is inadequate for the majority of potential users. To enable automated slicing a 3­D model and generating G­code for an acceptable path for GMAW 3­D printing, this paper reports on upgrading of the free and open source CuraEngine. The new slicer, MOSTMetalCura, provides the following novel abilities necessary for GMAW 3­D printing: i) change the perimeter metric from width to track count, ii) avoid movement that overlaps previous weld beads, iii) have infill start immediately after the perimeter finished and in the direction that eliminates translations, iv) add a variable pause between layers to allow for substrate cooling, v) configure GPIO pins to turn on/off the welder, and vi) set optimized wire feed speed and voltage of the welder based on printing speed, layer height, filament diameter, and tool track width. The process for initiating these changes are detailed and the new slicer is used to help improve the function of the printer for ER70S­6 steel. To find the printing function with the smallest bead width based on volume of material, the line width, layer height, and printing speed are varied to provide wire feed speed calculated by MOSTMetalCura, then the settings are used to print 3­D models. The results of 3­D printing three case study objects of increasing geometric complexity using the process methodology improvements presented, which show resolution of 1mm bead widths.