Why do weld guns sometimes stick to the part?

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On one machine some of the weld guns are sticking to the steel sheet metal part when production is resumed after a short break (a few minutes or more). After removing the stuck part normal operation resumes. Why is this and what can I do to fix this? Thank you - Steve

-- Stefan Shelander (Sstarstefan@aol.com), October 11, 2004


If this is galvanized, the answer could be this: When the surface of the part heats enough to cause the zinc in the galvanized coating to alloy with the copper, it makes brass. When you make brass between the tip and the part, you braze them together. Good water cooling is required to stop this. Titanium coated tips stop this, because the zinc won't alloy with them. I am puzzled by them sticking after a short break, is it possible that the tips get so hot in production that they keep the brass molten? A second cause could be that the cylinder slows down until it gets "warmed up". This, coupled with a short squeeze time could cause the tips to come together "hot", which will make them stick to any metal. Try a little more (10 cycles) of squeeze time to test this. -David Bacon

-- David Bacon (dbacon@updatetechnology.com), December 20, 2004.

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