Thermal management in WAAM through the CMT Advanced process and an active cooling technique. (September 2020)

• Record Type: Journal Article
• Authors: Scotti, Fernando Matos; Teixeira, Felipe Ribeiro; Silva, Leandro João da; de Araújo, Douglas Bezerra; Reis, Ruham Pablo; Scotti, Américo
• Is Part Of: Journal of manufacturing processes. Volume 57(2020)
• Page Start: 23
• Page End: 35
• Publication Date: 2020-09
• Subjects: WAAM -- Thermal management -- Active cooling -- CMT advanced; Production management -- Data processing -- Periodicals; Manufacturing processes -- Periodicals; Procestechnologie; Productietechniek; Production -- Gestion -- Informatique -- Périodiques; Fabrication -- Périodiques; Manufacturing processes; Production management -- Data processing; Periodicals; 670.5
• DOI: 10.1016/j.jmapro.2020.06.007
• Languages: English
• ISSNs: 1526-6125

Abstract

Graphical abstract: Highlights: Layer dimensions are mainly influenced by the CMT Advanced process polarity balance. Preform width consistency is highly favored by the active cooling technique. Preform porosity is not altered by the polarity balance and active cooling settings. Heat accumulation in the preforms is mitigated by the active cooling technique. The polarity balance governs the heat input, while the active cooling rules the heat sinking. Abstract: Thermal management is a key factor in wire + arc additive manufacturing (WAAM) in order to mitigate heat accumulation and cope with limitations regarding deposition cycle, geometry issues, and mechanical property anisotropies. From the process point of view, the variable polarity Cold Metal Transfer process, a variant of the Gas Metal Arc (GMA) deposition process named as CMT Advanced, stands out as a prominent option to reduce the heat transferred to the layers under deposition, without dropping the deposition rate. In another front, thermally managing the component by employing a technique called Near Immersion Active Cooling (NIAC) throughout all the deposition time has shown to be a promising tool to remove heat from the part under construction. Thus, the current work proposes an evaluation of the CMT Advanced process combined with the NIAC technique for WAAM. The deposition of Al alloy wall-like preforms was made by varying the positive and negative polarity ratio (EP/EN) in the CMT Advanced process and the layer edge to water distance (LEWD) in the NIAC technique. Comparative runs were made with natural cooling instead of the NIAC technique. Electric signals and porosity were quantified to verify the constancy of the process. Thermal cycles of a fixed point of the walls and some of their geometrical features were measured to see the effect of the EP/EN and LEWD parameters in terms of thermal management performance. For the deposition circumstances applied, minor lack of coalescence between layers and also adjacent discontinuities appeared in the waviness valleys of the walls. Such occurrences justified optical and scanning electron microscopy examinations at these locations as complement analyses. Even so, the results clearly showed that the EP/EN parameter is more influential in the control of the layer dimensions and of the preform surface waviness. The LEWD parameter has more effect on reducing the heat accumulation and, consequently, assuring no wall widening as the number of deposited layers is increased. Finally, it was inferred that the possibility of affecting the thermal cycles and geometries of the resultant preforms with two independent thermal management tools expands the windows for finding optimal deposition parameters in WAAM.