In resistance welding, contact resistance is a function of the extent to which two surfaces come in contact. Contact resistance is an important factor in the first few milliseconds of a weld. Combined with bulk resistance, the contact resistance value of the workpieces, electrodes, and their interfaces both cause and affect the amount of heat generated. The diagram illustrates three contact and four bulk resistance values, which, combined, help determine heat generated.
For more information, read our Fundamentals of Resistance Welding