Quote Originally Posted by thegary View Post
Take this for what its worth but I think I have an idea to try. I will say I have no experience with automated welding but I have welded for a long time. Have you tried to slow down the welding process by reducing both the feed speed and the amperage. I know this will slow down production and is not going to make management happy but I think it has merit . I would suggest cutting your amperage in half and adjust the welding speed down until you get the acceptable penetration needed. This will probably involve voltage adjustment also and will take some trial and error to get good results. To solve the cold start and the cracking at the beginning of the weld maybe you can program a pause in the feed rate for the start of the weld.
We have tried, it doesn't work.

Thank you everyone for your suggestions. We tried to produce another reference (pretty much the same, but with about 2mm less pipe diameter) and with no increased expansion. The welding looks the same but this time it doesn't crack on the ends. It's good for production. Regarding the reference we had problems with (the one on the photos), we will try to ask the supplier for longer plates, maybe about 1-1,5mm should be enough to prevent the cracking after the exagerated expansion we have to do.