Hi pros,
Several clients are asking us about welding possibilities with the UR. The main concern that I have is concerning the durability and reliability of such a system. I saw videos like this one below online where they place foils on top of the joint covers to make like a Faraday cage and therefore preventing electromagnetic noises to interfere with the servos. 
https://www.youtube.com/watch?v=nwAQvP6hg0c

Anyone using the UR for welding in industrial application? What are the pros and cons? What is the reliability of such a setup?

@Sebastien I have rarely seen foils being used to create a faraday cage around the robot's joints during welding, and I question the effectiveness of this kind of setup. I have personally never used a Universal Robots for a welding application, but I have used a UR5 for a painting application. Since we were worried about the paint particles affecting the robot's joints (even though they are supposed to be sealed) we were verifying the tool center point periodically to make sure that the robotic painting system continued to operate within the proper parameters.

@Stefan_Stubgaard Are the UR's joints sensitive to electromagnetic noise created by the welding gun? Are there any precautions or suggested maintenance for Universal Robots used in a welding environment? Like Sebastien I am interested in knowing if it is possible to use the UR for welding applications.

@Tim_Smith and @Sebastien Several customers are using UR robots for welding applications: https://www.youtube.com/results?search_query=universal+robot+welding

As long as you keep away from plasma welding it should be no problem to use a UR for spot, mig, mag, tig welding applications (I'm not a welding expert, so there might be other welding types that works as well).

Recommended precaution is to protect specially the plastic lids from the welding as the plastic potentially can be damaged if waste material drops on the surface. Protective cover in appropiate material can be used.

I would also make sure that the cable for the welding torch is mounted in the ceiling and not mounted along the arm, this is to reduce electromagnetic noise. Isolation of welding torch from the end of the robot arm by using non-leading material in between tool mounting and the torch is a solution I've seen as well.

It will be interesting to hear if any users have experience with welding and UR robots?