To adequately cool the electrodes we need to minimize their time at high temperatures so we need a lot of water flow. RWMA recommends 1.5 gallons/minute at the coldest temperature water available. Any compromise does not mean you will produce discrepant welds. It only means you will not produce as many good welds before dressing of the electrodes is required. This means down time in your production schedule which means fewer parts out the door each day. The recommended water flow rate is 1.5 gallons of water/minute per electrode. You can successfully produce good welds at 1.0 gal/min and 0.5 gal/min.
Water flow measurement is critical to insure that the components of the resistance welder and especially the electrodes are receiving the proper amount of cooling water during operation.
Open Drain - The simplest method if you are using an open drain is to run the exit water line from each component on the welder into a bucket for one minute and measure the water in the bucket. the ideal amount for the electrodes is 1.5 gallons/minute.
In order to lengthen electrode life, cooling the electrode is essential. The water temperature should be the colder the better for electrode life. A large amount of cold water is a requirement. The best temperature for the electrode is the coldest that you can provide. If your plant had a source of water from a well this would be perfect since the water would be about 50 something degrees Fahrenheit year round. While this is great for the electrodes, this temperature for the electrical equipment and electronics is not good during a humid summer. Electronics does not do well with condensation dripping all over it. Transformers may not hold up if they are sweating. So even though the electrodes might do well the weld machine might do poorly with lots of condensate.
Dressing an electrode means mechanically machining or forming the face of the worn electrode back to its original geometry. All resistance welding electrodes wear during use. In the case of spot welding this appears in the form of what is referred to as mushrooming. The weld face of the electrode begins to spread out perpendicular to the length of the electrode.
All electrodes wear and in the case of spot welding they mushroom. Therefor the face must be dressed back to original shape to maintain weld quality. If the weld face size is not controlled within some reasonable parameters there will be insufficient current to maintained the required weld nugget.
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