Development of a six-torch automatic welding system for aluminium vacuum chambers

Abstract

A novel automatic gas-tungsten arc-welding (GTAW) system has been developed at NSRRC for welding the aluminium (A6061-T651) vacuum chambers to be installed in an Ultra-high vacuum (UHV) system. This welding system has a XY stage that is built and configured to provide high-performance positioning along multiple welding axes. The automatic system comprises six welding torches to implement simultaneously two longitudinal side welds of an aluminium chamber, and is innovative in using computer-based software to control the welding movements and the welding energy of the six-torch output. In traditional single-torch welding, the key success factors focus on eliminating as much as possible the distortions of structural assemblies. The six-torch welding and the clamp-free approach together address the issue of reducing distortion and minimizing residual stresses with a novel one-step welding process. This paper introduces the mechanical configuration and the motion-control program. Real-time measurements for thermal and deformation monitoring to analyze the temperature distribution along the chamber surface are discussed. The welded chambers are tested with a leakage-free hermeticity test <5(10-10 mbar•L/s; the maximum deformation is controlled under 0.3 mm. © 2011 Springer-Verlag.