Identifying and Correcting Weld Problems.

A simple rule to remember is that quality usually equals consistency: welds that are always made within the specified weld lobe will consistently be of high quality. The question is, how can you determine if welds are being made consistently within the lobe?

If a weld control is programmed to deliver a certain amount of current at a certain amount of force, how can you ensure that the right amount of current and force was delivered at the tips? The amount of current coming out of the transformer may be correct, but is the current density at the workpiece where it should be? How do you know if the weld is good?

The most common method of answering these questions is through destructive testing. It's hard to dispute the quality of a weld after it has been pulled apart and inspected. However, destructive testing produces a lot of scrap metal, and while it will reveal whether the weld is good or bad, it cannot explain the specific details of why or how a weld turned out the way it did.

Resistance weld monitoring provides a way to see what is happening while each weld is being made. Critical parameters, such as resistance and current density, can be observed and measured at the workpiece during the weld process. The next chapter will discuss how this process works. These links provide an abbreviated guide of commonly encountered welding problems and their possible causes, adapted from documents published by the Resistance Welder Manufacturers' Association and reprinted with permission.

Recommendations for Producing Quality Welds

To produce high quality welds consistently, follow these tips:

1. Be sure that the electrodes you are using are suitable for the job.
2. Use standard electrodes whenever possible.
3. Select an electrode tip diameter suited to the thickness of the stock being welded.
4. Make use of flow indicators for viewing and assuring proper cooling water flow through the electrodes (typically, 1.5 gallons per minute).
5. Ensure that the internal water cooling tube of the holder projects into the tip water hole to within ¼ inch of the bottom of the tip hole.
6. Adjust the internal water-cooling tube of the holder to the appropriate height when switching to a different length tip.
7. Ensure that the top of the adjustable water-cooling tube in the holders is the proper height when changing to a different tip length.
8. Coat the tip with a thin film of cup grease before placing it in the holder to simplify removal.
9. Use ejector type holders for easy tip removal that won't damage the tip walls.
10. Clean the tip taper and holder taper on a regular basis, removing any foreign materials.
11. Perform dressing of electrodes on a regular basis to maintain the correct contour.
12. Use a rubber mallet to align holder and tips, rather than a metallic tool.

Avoid These Potential Sources of Weld Problems

1. Never weld using unidentified electrodes or electrode materials.

2. Avoid using special-purpose or offset tips if the job can be handled with a standard straight tip.

3. Do not use a small tip for welding heavy gauge materials or a large tip on small piece.

4. Do not overlook turning on the cooling water to the appropriate force when beginning to weld.

5. Never use a water hose that does not firmly fit the water connection nipples.

6. Avoid leaky, clogged or broken water connections.

7. Do not use holders that have leaking or deformed tapers.

8. Do not use electrode holders without an adjustable internal water cooling tube.

9. Avoid leaving the electrodes unused in tapered holder seats for long periods.

10. Do not use pipe wrenches or similar tools when removing electrodes.

11. Never dress an electrode using a coarse file. These recommendations can help improve the quality and consistency of your welds.