Bridging small gaps
In this type of application, we make use of the effect that the tungsten electrode, as it is automatically pulled back into the handpiece in one piece 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.
In this way, porosities, minor defects or a small hole can be easily sealed, sometimes without the use of welding wire.
In the latter case, however, the margins should not be thinner than 0.15 mm, as may happen if a framework is accidentally ground through at a preparation edge.
Otherwise, the hole would only be enlarged by welding.
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 VMK work.
Video: Filling a hole in a crown
You can also watch the procedure for closing small defects in this application video.