• Weld appears to last longer than the programmed time
• Machine welds twice before going up
• Machine continued welding until the e-stop was hit

Make sure the number of impulses was not doubled. This is a good trick when going to galvanized material. You just need to remember to turn it back for the next set-up. Also make sure that the foot pedal is released properly and that you are not in "Repeat mode". Re-check the weld schedule numbers because there have been cases of people getting the Weld Heat and Weld Time completely backwards in the program. If all the basics check out, you could have a very serious problem.

If the program, settings, and foot pedal all check out but the machine keeps welding, the timer is probably shot. If the unit is over 12 years old then replace it. On newer models this has only been the case after serious lightning strikes or in PC based PLC units that can not handle the EMF and EMI of the spot welding process. This is considered a very serious issue because the results can damage other components such as the SCR and TX. If the TX shorts out then the fuse should blow. If it doesn't you can have high voltage on the secondary and someone could get seriously hurt. If you have a "welding all the time" issue it could be the SCR has failed. SCRs normally fail in the closed position and that means they are on all the time. Click here for more information on SCR and TX trouble shooting.

Most of the time it is an operator or programming error. Hopefully you have the weld schedule written down and can reprogram quickly and easily.