Unitek Miyachi IP-215A User Manual page 76

APPENDIX D: RESISTANCE WELDING BASICS
Resistance Welding Parameters
Resistance welding heat is produced by passing electrical current through the parts for a fixed
time period. The welding heat generated is a function of the magnitude of the weld current, the
electrical resistance of the parts, the contact resistance between the parts, and the weld force
applied to the parts. Sufficient weld force is required to contain the molten material produced
during the weld. However, as the force is increased, the contact resistance decreases. Lower
contact resistance requires additional weld current, voltage, or power to produce the heat
required to form a weld.
The higher the weld force, the greater the weld current, voltage, power, or time required to pro-
duce a given weld. Low weld force usually results in lower bond strength. Increased weld force
requires higher energy but usually results in a stronger bond. Weld heat is proportional to the
square of the welding current (I), the total electrical resistance (R ), and the weld time (t), and is
t
inversely proportional to the contact area (A).
Welding Parameter Interaction
Figure D-1. Interaction between welding parameters.
IP-215A/IP-217A FINE SPOT WELDING POWER SUPPLIES
D-2 993-603 REV A: October, 1996