Bridging small gaps
In this type of application, we make use of the effect that the tungsten electrode, as it is automatically pulled back a little bit into the handpiece during the welding process, carries the molten material a little in this direction.
When welding in this situation, the handpiece or electrode is guided at a flat angle.
This method makes it easy to seal porosities, minor defects, or small holes – in some cases even without using welding wire. In the case of a hole, however, the edges should not be thinner than 0.15 mm – a situation that can occur, for example, if a framework is accidentally ground through at the edge of a preparation. Otherwise, welding would only make the hole larger.
This technical phenomenon also results in the fact that after a certain number of spot welds, depending on the alloy and the welding parameters used, deposits of the welded base material can be found on the electrode tip, which is why it has to be turned and reground from time to time. This is completely normal with this (as with all other) TIG welding processes.
Conversely, this means that if our devices are operated correctly (i.e. without pressing the electrode too firmly onto the workpiece surface during welding), no tungsten particles are introduced into the weld seam. This is good to know, especially for metal ceramics work (PFM).
Video: Closing a hole in a crown
You can watch the procedure for closing small defects also in this application video.