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Method and apparatus for monitoring and controlling a resistance welding operation

  • US 4,302,653 A
  • Filed: 04/02/1980
  • Issued: 11/24/1981
  • Est. Priority Date: 04/02/1980
  • Status: Expired due to Term
First Claim
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1. In a resistance welding controller having means for monitoring the resistance across a pair of weld electrodes and means for controlling the application of welding current to the electrodes, the method of controlling the formation of a weld including the steps of:

  • establishing a target weld resistance curve characterized by a predetermined minimum resistance value (target Rmin) and a predetermined rate of increase in resistance value (target dR/dt) during the initial heat-up phase of the weld, a desired decline in resistance value during the nugget growth phase of the weld (desired Δ

    R value), and a target weld time;

    monitoring the resistance of the weld and detecting the minimum resistance value (Rmin) of the weld and the subsequent rate of increase in resistance value (dR/dt) during the heat-up phase of the weld and comparing the observed values for Rmin and dR/dt with the target values for Rmin and dR/dt;

    dynamically correcting during the heat-up phase of the weld the weld current applied to said electrodes in accordance with said comparison; and

    terminating the weld when the desired Δ

    R value is satisfied.

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