Controls & Transformers
Questions and Answers
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.
During the resistance welding process the electrode face is subjected to extreme temperatures for short periods of time. To prevent premature wear, water cooling is necessary for the resistance welding electrodes. The technical term for this wear and resultant deformation is annealing. In the case of spot welding the face will begin to take on the shape of a mushroom. As this face grows the weld quality suffers and eventually weld quality failure occurs. Prevention or retarding this mushrooming is very important. One of the most important items to control is the time at temperature that the electrode weld face sees. One method of control is by cooling the electrode. The second benefit of this is that it will also cool and solidify the weld nugget during the hold period of the weld cycle.
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