Tweco FP-90 - Manual (Page 14)

The wire is pushed by a roll which is moved by a series of mechanisms. The roll has two grooves, one marked
by 0.035” (0.9 mm) and the other marked by 0.030” (0.8 mm). It is very important to use the correct groove as
explained in “Preparation for Welding” on page 9. Otherwise, the wire will not feed smoothly or it will be
crushed. Make sure that the torch tip matches with the wire diameter. Your welding power source is supplied
with a welding torch, complete with tip, for the wire included with the power source.
Follow the procedure described in “Installation of the Welding Wire” on page 7 for the replacement of the wire
spool.
WELDING TIPS
1. Keep the torch handle with a 45º angle with respect to the workpiece. Maintain the nozzle about 1/4” (6
mm) from the surface.
2. Move the torch handle with prudence and steadiness.
3. Keep the wire and its cover clean. DONOT use rusted wire.
4. Avoid sharp bends and kinks on the welding hose.
5. If possible, clean the wire liner with compressed air when replacing the wire spool.
6. Periodically, remove the dust using low pressure (3-4 bar/20-30 PSI) from the inside of the power source, to
assure adequate heat dissipation from power source during operation.
GENERAL OPERATING TIPS
Contact tips and nozzles should be cleaned frequently. Spatter buildup may cause bridging between nozzle and
tip. This could cause electrical shorting between the nozzle and the workpiece.
Regularly, inspect the conductor tube, handle, cable hose and other parts of the welding torch for abrasions,
cuts or undue wear. Replace or repair any parts found deficient.
ADJUSTMENT OF THE POWER SOURCE
Set the voltage. Use the correct “stick out.” The wire “stick out” is the distance between the contact tip and the
workpiece. The wire “stick out” (sometimes improperly called the arc length) should remain in the 0.2”-0.4”
(5mm-10mm) range to obtain the best welding (and sound) performance.
1. Position the voltage switch in the desired position (see Table 1). Select the lower position for thin material
and the higher setting for thicker material.
2. Adjust the wire speed. Start using a trial metal sheet thoroughly cleaned of layers of rust or paint. Connect
the ground cable to the workpiece. Adjust the wire speed at the high setting. Press the torch switch.
The FP-90’s welding torch is a “live” con-
tact torch and is ALWAYS IN THE POWER ON
POSITION. Wear eye protection at all times when
handling this torch.
Press the torch switch firmly to feed the wire.
Start welding and decrease the wire speed gradually.
Continue to decrease the wire speed and listen to the
sound. The sound changes from a crackling noise to a regular and strong buzzing (similar to
the sound of frying bacon). This buzzing sound indicates the correct wire speed for the work-
piece being welded. When the current regulation is changed, reset the wire speed. ALWAYS
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Figure 4: Power Source