Hello joa,

The processes for mold and die micro-welding are usually plasma and tig. They are very similar to the normal processes for these welds, except in scale. The welding of molds and dies require a very limited input of heat into the mold in order to maintain its integrity and minimize ANY distortion outside of the areas needing it. Most of the time a die or mold is only welded to repair an existing piece that performed OK, but has been damaged. Therefore, it is not normally a fusion process because filler material has to be added to build up the damaged area to higher than its original state in order to be remachined to its previous dimension. Here is a link for you with some technical info and some products made to produce micro-welds.

http://www.pro-fusiononline.com/

http://www.pro-fusiononline.com/products/workstation.htm

I haven't used their products, but the info there is pretty good. Hope this helps.