  New inventions change the approach of vacuum suitable welding for research
purpose. With orbital welding, laser welding and robot welding the
possibilities increase to fabricate larger vessels more accurately. Despite
this development there is still no perfect understanding on how to avoid
virtual leaks and how to make such joints suitable for dynamic stress. By
recalling its historical development, it is apparent how welding mistakes began
occurring systematically and how to avoid them. With ASDEX-Upgrade as an
example, it is shown how the attempt to conduct vacuum suitable welding has
decreased the fatigue strength. ITER could repeat the mistakes of ASDEX-Upgrade
even for unwanted welding (accidental fusing of joints).
