Effects of Longitudinal Arc Oscillation on Track Integrity During Collaborative Robot-Assisted Wire Arc Deposition

Abstract Collaborative robot-assisted wire arc additive manufacturing (COBOT-WAAM) is an advanced manufacturing process that integrates COBOT technologies with WAAM for the rapid production of large metallic components. This integration enhances manufacturing efficiency and allows for precise control of the track deposition process, which is essential for fabricating high-quality parts. Despite these advantages, maintaining track integrity during deposition remains a challenge due to a wide variation in WAAM process conditions. For example, at a high scanning speed molten pool becomes unstable degrading the integrity of the deposited tracks. In this research, this issue is addressed through the implementation of longitudinal arc oscillation. This method involves configuring collaborative robots to oscillate the deposition head in a back-and-forth motion that runs parallel to the travel direction while simultaneously depositing material. This approach allows for adjusting the amplitude and frequency of the oscillation to accommodate various materials and geometries, thus ensuring optimal melting and fusion of the deposited wire with the substrate or previously deposited tracks. A systematic methodology involving experiments using an in-house COBOT-WAAM system has been employed in this research to analyze the effects of varying arc oscillation parameters, including voltage, travel speed, amplitude, and wire feed rate on track integrity. Investigating these factors, particularly when employing longitudinal oscillation, can achieve the desired structural characteristics in the manufactured parts. Experiments are performed using stainless steel with Argon as a shielding gas. A confocal 3D microscope is utilized to obtain the 3D surface topography of the deposited tracks. Results indicate that the longitudinal oscillation can reduce the track discontinuity at higher scanning speeds. The findings prove that the productivity of the WAAM process can be enhanced without introducing track discontinuity defects by using longitudinal oscillation via a COBOT. In addition, it is found that adopting shorter oscillation amplitudes and reduced travel speeds effectively diminishes deposition defects, while increased amplitudes and travel speeds enhance this issue during oscillation deposition. Higher voltage and amplitude notably decreased track integrity, whereas reduced amplitude provided improved deposition conditions. Moreover, maintaining a constant voltage while increasing wire feed rates resulted in non-uniform deposition. Based on these experimental observations, several process maps are constructed indicating the safe and unsafe processing conditions for fabricating WAAM parts without track discontinuity.