Tweco 251 Thermal Arc Fabricator - Manual (Page 45)

FABRICATOR 251
Manual No. 0-4847 4-7 OPERATION
STITCH:
This mode of welding is used to weld two or more
components together with a stitch weld. The WELD
(Spot/Stitch) shaft controls the welding or ‘ON’ time
and the "DWELL (Stitch)" shaft controls the interval
or ‘OFF’ time for stitch welding. (Refer to Figure 4-6
for control).
Art # A-07428
Figure 4-8: Stitch Welding
4T (Latch):
This mode of welding is mainly used for long weld
runs, as the operator need only press the trigger to
activate the weld, then press the trigger again to stop.
This replaces the need for the operator to depress
and hold the trigger for the complete length of the
weld run.
WELD MODE WELD MODE
2T 2T
SPOT SPOT STITCH STITCH
4T 4T
Art # A-07427_AB
Figure 4-9: For Reference only
WELD (Spot/Stitch)
WELD MODE - SPOT
When the Weld Mode control is in the Spot position,
the Weld (Spot/Stitch) knob controls the duration of
a single spot weld.
WELD MODE - STITCH
When the Weld Mode control is in the Stitch posi-
tion, the Weld (Spot/Stitch) knob controls the length
of the stitch weld.
Art # A-07429_AB
WELD
(SPOT / STITCH)
t
MIN
1
5
7
9
3
2
4
6
8
Figure 4-10: Weld (Spot/Stitch) Control
Dwell Stitch
DWELL (STITCH) CONTROL KNOB
When the Weld Mode control is in the Stitch position, the
Dwell (Stitch) knob controls the length of the non-weld
portion of stitch welding.
Art # A-07430_AB
(STITCH) DWELL
t
MIN
5
7
12
3
2
4
6
8
9
10
11
Figure 4-11: Dwell (Stitch) Control
Burnback Control
Burnback time is the difference between the wirefeed
motor stopping and the welding current ceasing. The
Burnback time allows the electrode wire to burn out
of the molten metal weld pool. The Burnback time is
factory set for optimum performance. Burnback time
is adjusted by the knob of the potentiometer. Clock-
wise adjustment increases Burnback time.
BURNBACK BURNBACK
Art # A-07431_AB
t
Figure 4-12: Burnback Control