TY - JOUR

T1 - Development and evaluation of a closed-loop z-axis control strategy for wire-and-arc-additive manufacturing using the process signal

AU - Hölscher, Lennart Vincent

AU - Hassel, Thomas

AU - Maier, Hans Jürgen

N1 - Funding: Open Access funding enabled and organized by Projekt DEAL. Funded by the Ministry for Science and Culture of Lower Saxony (MWK) – School for Additive Manufacturing SAM. Funding Information: EWM AG is thanked for providing a state-of-the-art welding power source for these investigations.

PY - 2023/9

Y1 - 2023/9

N2 - Wire-and-arc-additive manufacturing (WAAM) is an additive manufacturing technology with a high deposition rate. WAAM usually employs a layer wise build-up strategy. This makes it necessary to know the height of each deposited layer to determine the height the z-axis has to travel after each layer. Current bead geometry models (BGM) lead to variations, which can gradually accumulate over the layers. The present study focuses on the development of a closed-loop control system capable of keeping the contact tube working distance (CTWD) constant during short-circuit gas metal arc welding (GMAW) based WAAM. The algorithm calculates the CTWD based on the resistance during the short circuit. The closed-loop strategy is compared to an open-loop control strategy, which moves along a predefined height step after each layer. Using the proposed control strategy, WAAM becomes a fully automated process without the need for preliminary experiments to determine the height step. Only a short calibration slope is necessary for a complete closed-loop additive build-up. To study the influence of the control strategy on the workpiece the energy input, mechanical strength, microhardness, porosity, and microstructure were analyzed. It is shown that the CTWD of the open-loop deposited component increases slowly. Due to the novel control approach, this is prevented by the closed-loop control, while the mechanical strength and microhardness remain.

AB - Wire-and-arc-additive manufacturing (WAAM) is an additive manufacturing technology with a high deposition rate. WAAM usually employs a layer wise build-up strategy. This makes it necessary to know the height of each deposited layer to determine the height the z-axis has to travel after each layer. Current bead geometry models (BGM) lead to variations, which can gradually accumulate over the layers. The present study focuses on the development of a closed-loop control system capable of keeping the contact tube working distance (CTWD) constant during short-circuit gas metal arc welding (GMAW) based WAAM. The algorithm calculates the CTWD based on the resistance during the short circuit. The closed-loop strategy is compared to an open-loop control strategy, which moves along a predefined height step after each layer. Using the proposed control strategy, WAAM becomes a fully automated process without the need for preliminary experiments to determine the height step. Only a short calibration slope is necessary for a complete closed-loop additive build-up. To study the influence of the control strategy on the workpiece the energy input, mechanical strength, microhardness, porosity, and microstructure were analyzed. It is shown that the CTWD of the open-loop deposited component increases slowly. Due to the novel control approach, this is prevented by the closed-loop control, while the mechanical strength and microhardness remain.

KW - Closed-loop control

KW - Gas-metal-arc welding

KW - Height step

KW - Process control

KW - Wire-and-arc-additive manufacturing

UR - http://www.scopus.com/inward/record.url?scp=85167645620&partnerID=8YFLogxK

U2 - 10.1007/s00170-023-12012-w

DO - 10.1007/s00170-023-12012-w

M3 - Article

VL - 128

SP - 1725

EP - 1739

JO - The international journal of advanced manufacturing technology

JF - The international journal of advanced manufacturing technology

SN - 0268-3768

IS - 3-4

ER -