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Method of ensuring the maintenance of constant quality of spot welds

  • US 4,329,561 A
  • Filed: 02/14/1979
  • Issued: 05/11/1982
  • Est. Priority Date: 12/11/1975
  • Status: Expired due to Term
First Claim
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1. A method of improving the reproducibility of the welds produced by an electric spot welding machine, which comprises(a) passing a preheating current of lower magnitude than a subsequent welding current through the workpieces to be welded;

  • (b) monitoring the resistance of the weld starting with the first cycle of preheating current;

    (c) determining when the rate of decrease of the total weld resistance has fallen below a predetermined limit; and

    (d) then switching over from said preheating current to said welding current.

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