Spot Welding

Questions and Answers

This question has already been answered by another article in this blog.

"WHY DO I HAVE SURFACE EXPULSION?"

The only additional comment is that the galvanized zinc coating melts at a low temperature and is very prone to expulsion and could contribute to the popping sounds. This could be item 5 under least prevalent causes. Otherwise below is:

"WHY DO I HAVE SURFACE EXPULSION?"

Surface expulsion is caused when the part surface heats up. So anything which would cause this, could be a reason. The appearance is similar to interface expulsion. In this case we are looking for conditions which cause the contact surface heat to be high.

Surface Expulsion Electrode Sticking

 

This question is a sales marketing question which is beyond the scope of this blog.

I can suggest contacting your local resistance welding supplier or the:

RESISTANCE WELDING MANUFACTURERS ALLIANCE “RWMA”

OR

AMERICAN WELDING SOCIETY “AWS”

    Full Size and Cap Electrode rev

FULL SIZE ELECTRODE AND MALE CAP

This question is not clear to the author of this blog. Resistance welding materials are classified by their material compositions and properties. In North America the Resistance Welding Manufacturers Alliance (RWMA) and American Welding Society (AWS) publish this data.

RWMA Resistance Welding Manual 4th Edition

AWS Standard J1.3 Specification for Materials Used in Resistance Welding Electrodes and Tooling

This blog has various articles describing the various material Classes of resistance welding electrode materials specified by the RWMA.

    Full Size and Cap Electrode rev

FULL SIZE ELECTRODE AND MALE CAP

Specifications of common designs, specifications, application and common uses are also described in the referenced documents and articles. Similar documents are published by ISO and Asian standards organizations.

Reference: RWMA – Resistance Welding Manual 4th Edition
                  AWS Standard J1.3 Specification for Materials Used in Resistance Welding Electrodes and Tooling

Indentation is defined as the depression made by the electrode into the outer surface of the part being resistance welded.

 Indentation

The figure above defines indentation. The product being welded in many cases may define the amount of indentation allowed. A show surface like the hood of an automobile would be a no-show surface therefor no indentation is acceptable on the face side. This is commonly refered to as a cosmetic weld (one side has little of no indentation).  On a weld surface inside the trunk or under the hood, indentation may be acceptable at some level.

Everyone looks for a formula to set squeeze, weld, hold and off, but it basically does not exist. Equipment varies with different impedances, conductors, electrodes and tooling. Several articles have been written on this subject in the blog:

"HOW DO YOU SET THE PROPERS QUEEZE TIME IN A RESISTANCE WEDING SCHEDULE?"

"IS THERE A FORMULA TO DETERMINE THE SQUEEZE TIME IN RESISTANCE WELDING?"

"IS SQUEEZE TIME IMPORTANT?"

"HOW WILL HOLD TIME CHANGE THE RESISTANCE WELD STRENGTH?"

 Spot Weld Schematic

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