Controls & Transformers
Questions and Answers
Repeat or pulsing refers to repeating the weld and hold portion of a weld schedule. Normally there is a very short off period of one or two cycles with continued application of force between the two weld sequences. This gives you the ability to dissipate the heat energy a little further into the part away from the center of the weld nugget.
Squeeze is the first segment of the weld schedule. It’s function is to apply force on the work pieces to bring them together. This pressure under the face of the electrode in turn makes good electrical contact and controls and contains the resultant weld nugget during the weld and hold portion of the weld cycle. If current is applied prematurely before the proper force has been reached these functions will be compromised and expulsion and poor nuggets should be expected.
Squeeze time is the first sequence of a weld schedule. It is designed to allow the electrodes to close and build up full force on the parts before current is applied. If squeeze time is too long it does not hurt the welding operation but it does increase the cost of the total operation by increasing the total time of the weld schedule and thus fewer parts per shift.
Edge distance is a very important design criteria in resistance welding. Any weld on an edge can expel metal and or result in a partial weld nugget. This type of weld is considered deficient in quality programs. Edge welds should be avoided in all design and set up situations.
Burrs on the edges of stampings can cause problems because they prevent the part from seating properly or the burrs can break off and become particles which can be expelled during the welding operation.
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