Method for monitoring and regulating electrical resistance welding

• US 3,932,725 A
• Filed: 02/28/1974
• Issued: 01/13/1976
• Est. Priority Date: 03/27/1973
• Status: Expired due to Term

• Current Assignee: KUKA Schweissanlagen + Roboter GmbH
• Original Assignee: Keller & Knappich Augsburg Zweigniederlassung Der Industrie-Werke Karlsruhe Augsburg AG
• Inventors: Ganowski, Franz-Josef
• Primary Examiner(s): Truhe, J. V.
• Assistant Examiner(s): Shaw, Clifford C.
• Application Number:
  US05/446,849
• Time in Patent Office: 684 Days
• Field of Search: 219/109, 219/110, 219/117
• US Class Current: 219/110
• CPC Class Codes: B23K 11/25 Monitoring devices

Abstract

A method for monitoring and regulating electrical resistance welding by comparing the actual values obtained by integrating measured values of the welding electrodes with desired valued limits obtained by test welding operations in the form of voltage and current parameters. These parameters are integrated in accordance with the formula ##EQU1## WHEREIN Y IS OTHER THAN UNITY AND IS SELECTED SO THAT THE INFLUENCE OF THE RESISTANCE R on the actual, measured value is at least equivalent to the influence of the current I and/or the welding time t, in the above formula, on the measured value. The resultant weld value is then fed to a comparison circuit which contains the upper and lower limits obtained by the test welding. If these limits are exceeded the power to the welding apparatus is automatically disconnected.

Claims

1. A method for selectively monitoring and regulating electrical resistance welding processes by comparing actual, measured values with desired value limits, the latter being a measure of acceptable welding quality, comprising the steps of:

conducting at least one test welding operation to establish the desired value limits, while the actual values are obtained during an actual welding operation;

the desired value limits relating to the secondary welding current I, the resistance R between the welding electrodes, as well as the welding time t measured during a single actual welding operation;

measuring the voltage across the electrodes, and the current applied thereto, during the actual welding operation;

integrating the actual values of the voltage and the current to produce a welding result, by interpolation of both the actual and the desired values in the formula;

##EQU4## wherein I is the secondary welding current in amperes,

R is the resistance between the electrodes in ohms,

Y is an exponent other than unity, and

t is the welding time in seconds;

the current, the resistance and the time being subject to unavoidable and tolerable fluctuations in predetermined ranges during the actual welding operation;

selecting the magnitude of the exponent so that the influence of the resistance on the desired value limits is at least equivalent to the influence of at least one of the current and the welding time on the same value limits when the former fluctuate within the predetermined ranges;

comparing the actual values with the desired value limits; and

at least partly disconnecting electrode power when the actual values meet or exceed the desired value limits.