Section 4 Operation - ESAB MigMaster 250 Instruction Manual

sectIon 4
C. Set the "coarse" and "fine" Voltage control switches
and wire speed pot to the desired settings and begin
welding operation as described in Sections 4.3.2 and
4.3.3.
4.2.3.3 sPot WelDIng MoDe oPeratIon
A. Place the three-position toggle switch in "Spot" posi-
tion.
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
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 moment
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 techniques
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).
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oPeratIon
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