CHAPTER 3: USING UB25 WELDING FUNCTIONS
UB25 LINEAR DC RESISTANCE WELDING CONTROL
3-12 990-665
Pre-Weld Check
Application
• Detect Misaligned or Missing parts.
Function
This is used to see if parts are misaligned or missing before a welding pulse is delivered to the weld
head. If a part is missing or misaligned, you do not want the machine to weld because the result
would be an unacceptable weld and/or damaged electrodes.
Pre-Weld Check is similar to Energy Limits, however in this case Pulse 1 should be very short
(1-2 milliseconds), and the current should be low, about 10% of the Pulse 2 current. Pulse 1 should
be used as a measurement pulse and should not perform a weld.
Pre-Weld Check Waveform
Example: To detect misaligned parts, use constant current and set upper and lower voltage limits for
Pulse 1 If parts are misaligned, the work piece resistance will be higher, so the voltage will be higher.
If parts are missing, voltage will be lower. In either case, the Pulse 1 upper or lower limits will be
exceeded, and Pulse 1 can be inhibited.
NOTE: You must have upslope programmed into the pulse in order to set a lower limit.
In addition to inhibiting the weld, the Power Supply has four programmable relay outputs which can
be used to trigger alarms to signal operators of weld faults or signal automation equipment to perform
pre-programmed actions, such as stopping the assembly line so the faulty weld piece can be removed.
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