Troubleshooting Resistance Welding: Seven Simple Steps

May 18, 2024
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Imagine: You’ve been successfully running the same resistance spot welding (RSW) program for days, months or even years when suddenly it stops working properly. The typical symptoms of a process gone wrong include:

  • Weak welds
  • Insufficient nuggets
  • Sparking
  • Metal expulsion
  • Parts overheating
  • Electrode sticking
  • Discoloration
  • Inconsistent results.

Troubleshooting ToolWhat do you do? Where should you start? It is easy to panic and jump to suspected issues, but a calm methodical approach will win out every time.

A successful weld occurs when the metal former maintains the proper process settings, receives the correct material, and the equipment is functioning correctly. With a successful process defined, metal formers should then thoroughly document the process, and save a few sample material pieces for future reference. The process audit worksheet (or PAW, included here) provides a guide to fully document a RSW process. 

When trouble in the process arises, start the troubleshooting process by referring to the PAW, starting with the “business end”—material and electrodes—and working backward from there. These seven steps provide every operator and process engineer with a methodical approach to troubleshooting an RSW process: 

Process Audit Worksheet1. Check the parts being welded. Is your supplier still providing the same base materials, plating process, etc.? If a new lot of materials has begun to cause problems, go ahead and weld some parts from a previous lot and see if they still weld properly.

2. Examine the electrodes and ensure that the electrode material, size and shape have not changed. Also, inspect electrode condition and review the resurfacing procedure.

3. Ensure that the fixturing/tooling has not been modified or damaged and that it holds the parts in the proper welding position.

4. Inspect the electrode holders to ensure that they properly clamp the electrodes; check the weld-head motion for friction that might cause problems with follow-up; inspect all of the electrical connections from the electrode holders, power bars and weld cables to the power-supply output terminals; and check the mounting location of the voltage-sensing cables, ensuring that they are screwed down tight.

5. Check the power supply, ensuring that it is connected to the correct line voltage and not giving any alarms. All of the electrical connectors should be secure. 

6. Verify all of the process settings, including the power-supply schedule, menu settings, and weld-head force and speed settings.

7. Ensure that the operators continue to follow proper procedures, including electrode maintenance, part handling and machine initiation. Take care to properly train new operators on these and other tasks:

  • How to handle and align the parts
  • How to maintain and change the electrodes
  • Knowing the quality and inspection requirements
  • Knowing the relevant production testing methods and monitoring requirements.

In most cases, one of these seven tips will resolve the issue and you can quickly get back to production. If there are still issues with the process, then it is possible that the process was initially setup incorrectly—or the process window was exceedingly small. If this is the case, then development of a new process will be required. MF

Article contributed by Amada Weld Tech, Monrovia, CA; www.amadaweldtech.com.

Industry-Related Terms: Case, Discoloration, Electrodes
View Glossary of Metalforming Terms

 

See also: Amada Weld Tech Inc

Technologies: Welding and Joining

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