Page 57 - MetalForming Magazine June/July 2022 80th Anniversary Issue
P. 57

 Fabrication: Resistance Welding
and walking around the plant so that they could show me the various weld- ing guns that had experienced the issue. In a few cases, they had identical welding guns on the left and right side of the production line and the gun on one side had good electrode life while the gun on the other side experienced poor electrode life.
“I asked them to remove the caps on each of the two guns and we found that, on the gun with poor electrode life, the small brass water tube feeding water from inside the gun arm into the electrode cap adaptor had broken off. We then took apart 16 more guns expe- riencing electrode-life issues and found that the tubes were missing on all of them. Without the short 1.5-in. brass tube installed, cooling water was not getting out to the end of the cap adap- tor and into the caps. Some water did squirt across the gap and found its way into the cap, but not much.
“After they replaced all of the miss- ing brass water tubes, a week later the
typically only 6-10 V—the dope or tape used to stop a water leak also serves as an electrical insulator and prevents welding current from flowing through the joint. This problem can prove espe- cially hard to identify if the mainte- nance person carefully trims the white plumber’s tape so it doesn’t show.
CRWT Training
Want to learn more about the RW process and hopefully prevent these and other costly gotchas? Check out the training courses offered by the Resistance Welding Manufacturing Alliance, a standing committee of the American Welding Society (AWS), and other venders. Once trained, consider taking the 100-question AWS exam, leading to recognition as a Certified Resistance Welding Technician (CRWT). MF
In addition to Don DeCorte of RoMan Manufacturing, Matt Post of T. J. Snow Co. also contributed to this article.
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plant manager told me it was a ‘mira- cle’—electrode-cap life was good on all of the guns. He estimated that they had been running with missing tubes for 5 months, while the welding engi- neers and maintenance guys argued about electrode-cap alloys, cap dimen- sions and cap dressers. Instead, the problem was a $2 part that they replaced in 10 min.
“The plant’s maintenance manager said that the simple issue of missing water tubes had likely cost them $50,000 in additional electrode-cap usage and lost production.”
A Dopey Gotcha
Another common gotcha related to water cooling results from well-meaning maintenance personnel who use pipe dope or plumber’s tape to solve the common problem of water leaking from the threaded copper electrode adaptor or tapered electrode-holder socket.
Because the secondary output volt- age of an RW machine is very low—
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   54 MetalForming/June/July 2022
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