How much material can be dressed from an electrode cap face before failure?

It is a common practice to dress resistance welding caps used in robotic and job shop applications. Many dress at breaks or shift changes. In automated operations some dress a very small amount between each part as the line moves. The goal is to maintain a relatively consistent electrode face welding the part. At some point a limit to the material removal is reached and the cap must be changed. The question is:

How much material can be removed before the cap will fail to function?

The assumption is that the dressing removes all surfaces problems and the part is functional. The only consideration is face to waterhole material thickness. Obviously dressing into the water hole is too far. In a nonscientific test observed personally, it was pointed out that the facing thickness is the controlling factor.

When the face thickness is not strong enough to withstand the weld force being applied the electrode face will collapse. Electrode or cap dressing must end before this.  Obviously this face thickness can be affected by the face design of the cap or electrode.

Many end users specify a dressing ring on the cap. Some companies have standard parts with the dressing rings as standards. Some of the rings are limits. Other rings mark the water hole. The actual testing and verification of their functionality is beyond the scope of this blog.

Reference: RWMA – Resistance Welding Manual 4th Edition

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