Amada HF-2500A, Operation Manual, Page: 62 / 164

CHAPTER 4: INTRODUCTION TO FEEDBACK MODES AND MONITORING
HF-2500A HIGH FREQUENCY WELD CONTROL
4-6 990-371
The use of a current limit monitor for the first pulse enables the pulse to be terminated when a
predetermined amount of current flow is achieved. The rise of the current to a consistent level ensures a
consistent resistance at the beginning of the second pulse. Depending on the initial resistance, the amount
of time required to bring the resistance down will vary from weld to weld. The first pulse, therefore,
should be programmed to be much longer than generally required to ensure that the current limit is always
reached. The power supply will terminate the pulse based on the reading of current in the power supply’s
monitor.
3. 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.
When using a
Pre-Weld Check,
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.