1
Introduction
Page 4
Stud welding unit
operating manual
Date:
July 2021
ALPHA 850
07.2021 / EN
Rev.:
A
1.4 Process
When welding according to the drawn arc and short cycle drawn arc processes, a
welding gun loaded with appropriate studs must be placed to the workpiece surface
at a right angle, to the degree possible.
Pressing the gun to the workpiece slides the stud back with the weld axis around
the stud stick out.
When the weld command is given, the pilot current flows over the short circuit path
of the stud and workpiece. The welding gun’s coil lifts the stud against the force
workpiece’s pressure spring.
When the weld stud is lifted from the workpiece, first an auxiliary arc is drawn and
then the main arc is ignited.
During the lift movement, the arc melts the front surface of the stud and a surface of
approximately the same size on the workpiece, so that a pool of liquid melt occurs
on the surfaces to be welded.
When the set weld time is over, power is cut off to the gun coil, so that the stud is
accelerated back onto the workpiece.
Immersion of the stud into the weld pool extinguishes the main arc and the weld
current is shut off. Before the melt bath stiffens, the stud is pressed into the still
liquid melt.
Immediately after, the welding gun is pulled from the cooled stud and can be
reloaded.
Process diagram:
1.
Placing the
2.
Pulling the
3.
Igniting the
4.
Immersing the
5.
End of
weld stud
auxiliary arc
main arc
weld stud
weld
The weld time in the short cycle drawn arc process is about 10 ms –
100 ms.
The weld time in the drawn arc process is about 100 ms – 1000 ms.
