Method and apparatus for measuring and controlling indentation in resistance welding

In a resistance welding system in which at least one electrode assembly, comprising an electrode secured to an electrode holder, is used to hold at least two workpieces together and to apply a weld pulse to said workpieces, wherein the electrode situated in said one electrode assembly will abut against a surface of one of said workpieces over a contact area located on said surface during a welding operation;

• a method for measuring indentation occurring in said surface during said welding operation comprising the steps of:
• applying an appropriate force to said electrode assembly to squeeze said workpieces together;
• applying a weld pulse to said workpieces;
• determining, at least while said weld pulse is applied to said workpieces, a change in a distance separating a pre-defined location on said electrode assembly and a region situated on said surface, wherein said region is adjacent to said contact area but is not substantially indented by the electrode during said welding operation;
• and
• producing, in response to said change, at least one corresponding measured value of indentation.

In a resistance welding system for welding at least two workpieces together, apparatus for measuring indentation occurring in at least one of said workpieces during a welding operation and for controlling a weld pulse used therein, said apparatus comprising:

• at least one electrode assembly, comprising an electrode secured to an electrode holder, for holding at least two workpieces together and for applying a weld pulse to said workpieces, wherein the electrode situated in said one electrode assembly will abut against a surface of one of said workpieces over a contact area located on said surface during said welding operation;
• means for applying said weld pulse to said one electrode assembly;
• means, having at least one sensing device wherein said one sensing device is secured to said one electrode assembly at a pre-defined location thereon, for determining, at least while said weld pulse is applied to said workpieces, a change in a distance separating said sensing device and a region situated on said surface, wherein said region is not substantially indented by the electrode during said welding operation;
• means, responsive to said change, for producing a corresponding measured value of indentation;
• and
• means, connected to said applying means, for controlling said weld pulse in response to said measured value of indentation.

In a resistance welding system in which at least one electrode assembly, comprising an electrode secured to an electrode holder, is used to hold at least two workpieces together and apply a weld pulse to said workpieces, wherein the electrode situated in said one electrode assembly will abut against a surface of one of said workpieces over a contact area located on said surface during a welding operation;

• a method for measuring indentation occurring in said surface during said welding operation and for controlling the weld pulse, said method comprising the steps of:
• applying an appropriate force to said electrode assembly to squeeze said workpieces together;
• applying a weld pulse to said electrode assemblies;
• determining, at least while said weld pulse is applied to said workpieces, a change in a distance separating a pre-defined location on said one electrode assembly and a region situated on said surface, wherein said region is adjacent to said contact area but is not substantially indented by the electrode during said welding operation;
• producing, in response to said change a corresponding measured value of indentation;
• and
• controlling said weld pulse in response to said measured value of indentation.