Should I use a full size or cap resistance welding electrode?


Full Size and Cap Electrode rev


The choice of cap vs full size standard electrode comes down to job shop, frequent set ups and length of production runs. Caps are the choice for long runs or in highly automated facilities. Full sized electrodes are the norm in job shops where short runs and frequent job changes are the norm.

Full size electrodes and male or female resistance welding caps of the same size perform the same functions. They deliver current, force and cooling to the work piece through the electrode face. As the nugget begins to grow the force helps control this growth and the cooling water protects the electrode face. When the current is turned off force is maintained and the continuous cooling water inside the electrode dissipates the heat to cool and solidify the weld nugget and help maintain electrode life.

Full size electrodes are generally used in job shops where many different parts can be run on the same electrode and or many short runs are anticipated. With proper dressing they will last for many thousands of welds and are relatively easy to change for another set up. They are most frequently used on press welders. 

Male and female resistance welding caps are used on press welders or automated equipment and robots weld guns. Because resistance welding caps are smaller than full size electrodes they contain less copper and cost less to purchase. They can be dressed but even with dressing will not produce as many welds as a full size electrode before end of life. In most cases they are used because they are on high volume, long running automated jobs. They usually can last a shift or a day at most facilities to keep their lines up and running before a cap change is required.

Reference: RWMA Resistance Welding Manual 4th Edition

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