Crater Filling - ESAB MEK 4 Service Manual

3

Crater filling

The crater fill function can be used when the MEK 4 is working
with a LAW power unit.
The crater fill function comprises the following modules :
An input for selecting crater fill function On/Off.
S
Closing switch SA02 activates the function.
Potentiometer RP04 sets the crater fill time.
S
Times between 0 and 5.1 seconds can be set.
An output, XP01;W, which supplies a signal to the power unit when the voltage
S
is to be reduced for crater filling.
The emitter of the transistor in optocoupler IC10 is connected to 0 VB, i.e. to
the neutral of the power unit voltage reference.
The crater fill function operates as follows :
Phase 1
When in 2- - stroke control mode, releasing the welding gun trigger switch reduces the
wire feed speed to 84% of its original value. In 4- -stroke control mode, crater filling
starts when the trigger switch is pressed for the second time. Optocoupler IC10 is
activated, supplying a signal to the power unit that crater filling has started, causing
the power unit to reduce its output voltage.
Phase 1 continues for a time as determined by the setting of potentiometer RP04, up
to a maximum of 1.27 seconds.
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