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- da Silva, Leandro João, et al.
(author)
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Concept and validation of an active cooling technique to mitigate heat accumulation in WAAM
- 2020
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In: The International Journal of Advanced Manufacturing Technology. - : Springer Science and Business Media LLC. - 0268-3768 .- 1433-3015. ; 107:5-6, s. 2513-2523
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Journal article (peer-reviewed)abstract
- This work aimed at introducing and exploring the potential of a thermal management technique, named as near-immersion active cooling (NIAC), to mitigate heat accumulation in Wire + Arc Additive Manufacturing (WAAM). According to this technique concept, the preform is deposited inside a work tank that is filled with water, whose level rises while the metal layers are deposited. For validation of the NIAC technique, Al5Mg single-pass multi-layer linear walls were deposited by the CMT® process under different thermal management approaches. During depositions, the temperature history of the preforms was measured. Porosity was assessed as a means of analyzing the potential negative effect of the water cooling in the NIAC technique. The preform geometry and mechanical properties were also assessed. The results showed that the NIAC technique was efficient to mitigate heat accumulation in WAAM of aluminum. The temperature of the preforms was kept low independently of its height. There was no measurable increase in porosity with the water cooling. In addition, the wall width was virtually constant, and the anisotropy of mechanical properties tends to be reduced, characterizing a preform quality improvement. Thus, the NIAC technique offers an efficient and low-cost thermal management approach to mitigate heat accumulation in WAAM and, consequently, also to cope with the deleterious issues related to such emerging alternative of additive manufacturing.
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| 2. |
- Scotti, Fernando Matos, et al.
(author)
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Thermal management in WAAM through the CMT Advanced process and an active cooling technique
- 2020
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In: Journal of Manufacturing Processes. - : Elsevier Ltd. - 1526-6125. ; 57, s. 23-35
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Journal article (peer-reviewed)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. © 2020 The Society of Manufacturing Engineers
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