ESAB MIGMASTER 250, Instruction Manual

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C. Set the “coarse” and “fine” Voltage control
switches and wire speed pot to the desired settings
and begin welding operation as described in Sec-
tions 4.3.2 and 4.3.3.
4.2.3.3 SPOT WELDING MODE OPERATION
A. Place the three-position toggle switch in “Spot”
position.
B. Replace the standard nozzle with the No. 12 Spot
weld Nozzle P/N 999625.
C. Trim the welding wire back so the end is slightly
inside the nozzle.
D. Set the “coarse” and “fine” voltage control switches,
wire speed, and the Spot-Stitch Weld Time see
Table 4.3, for the thickness of the metal being
welded and the diameter of the weld wire being
used.
E. To spotweld:
i. Press the torch nozzle squarely on the top plate.
Apply enough pressure to hold the two pieces of
metal firmly together, so there is no loose play
between them.
Fig. 4.2.3 - Cross Section of Good Spotweld
ii. Pull the trigger, holding the gun motionless and
firmly. The electrode wire and shielding gas will
be fed to the work, and the arc will be maintained
for the length of time set in Step D. above.
iii. After the preset time has elapsed, the wire will
stop feeding, the arc will be broken, and the
shielding gas will stop flowing.
A good spotweld will penetrate through both lay-
ers of metal, and will have a small nugget on the
reverse side, (Fig. 4.2.3)
4.2.4 STITCH WELDING MODE OPERATION
A. Place the three-position toggle switch in “Stitch”
position. The stitch weld mode uses a series of pre-
timed arc-on/arc-off time sequences to allow cooler
welding.
B. Be sure a standard nozzle (and not a spot weld
nozzle) is installed on the torch.
C. Set the length of time the arc will be ON for each
sequence by adjusting the Spot-Stitch Weld Time
control on the power supply’s front panel. This
timer has an approximate range of from 0.4 seconds
at the minimum setting to 3.5 seconds at the
maximum setting. Set the length of time the arc will
be OFF for each sequence by adjusting the Stitch
Weld Time control on the front panel. This timer
has an approximate range of from 0.4 seconds at
the minimum setting to 3.5 seconds at the maximum
setting.
D. Set the “coarse” and “fine” voltage control switches
and wire speed as specified in Table 4.3 under
Continuous Weld Conditions for:
i. The type weld being made (see diagrams to the
left of each column of figures).
ii. The thickness of the metal being welded.
iii. The gap (if any) between the pieces being weld-
ed.
iv. The diameter of the welding wire being used.
E. When using the Stitch weld mode, before starting
the weld the welding wire should extend about
1/ 2-in. beyond the end of the nozzle. Adjust this
length by either clipping off the end of the wire with
insulated cutters or by using the torch switch.
Power supply contactor becomes energized the mo-
ment the torch trigger is depressed. Arcing can
occur if the wire is brought to a ground. Keep the
torch always from ground until welding is to begin.
F. During the welding, use the same welding tech-
niques as described in Section 4.3.3 and 4.3.4.
4.2.5 DUTY CYCLE (Figure 4.2.5)
The duty cycle of the equipment is the percentage of a 10
minute period which it can operate safely at a given output
current. The Migmaster system is rated at 50% duty
cycle. This means that the equipment can be safely
operated at 250 amperes for five minutes out of every 10.
This cycle can be repeated indefinitely (See Figure
4.2.5).
SECTION 4 OPERATION