Cold welds after a few minutes of production and needs to increase the current.
Summary
Your cooling system has to be checked and / or one or more circuits need to be cleaned.
Explanation:
If the temperature difference exceeds a certain value, mechanical mis-alignments may occur which can affect the welding geometry (see related article). Obviously it is not the same when a welder is cold (start of production) and hot (after up to one hour of production).