Prima MIG 204 Manual De Uso página 14

8.0 WELDING PREPARATION
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Connect the ground cable to the proper female outlet on the bottom right-hand corner of the welder (on some models the ground cable is already
connected). Attach the ground clamp to the bare metal to be welded, making sure of good contact;
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Make sure that the wire-roller groove in the roller corresponds to the diameter of the wire being used. Refer to paragraph 4.
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Plug the machine into a suitable outlet.
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Open the gas valve on the gas cylinder regulator, (turn knob clockwise) and adjust the gas regulator to the proper setting position. Note: this
varies with different metals, thicknesses and currents.
9.0 OPERATION
A certain experience is required to adjust and use a Mig power source. In mig welding two parameters are fundamental: the welding voltage and the wire
speed. The resulting welding current is a result of these two settings.
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Set the voltage and wire feed controls to positions suitable for the thicknesses of the material to be welded.
Wedling current varies in relationship to wire feed speed. For low welding current output, the wire feed speed potentiometer should be set
at the low end of the wire feed speed scale.
Turning the wire feed speed control potentiometer clockwise, will result in increased wire feed speed and welding current. Welding voltage is
adjusted to match the wire feed speed (welding current).
Progressively select higher voltage positions with increasing in wire speed.
Increase of the welding voltage leads to a longer arc (without substancially affecting the current). Conversely, a decreased welding voltage results in
a shorter arc (the current again is not substancially changed).
A change in wire diameter results in changed parameters. A smaller diameter wire requires an increase in wire feed speed to reach the same current.
If certain limits are exceeded, a satisfactory weld cannot be obtained. These are:
A ) A too high wire feed speed (too high with regard to the welding voltage) results in pulsing within the torch. This is because the wire electrode
dips into the puddle and cannot be melted off fast enough.
B) A too high welding voltage (too high with regard to the wire feed speed), will result in excessive and unstable arc. By increasing still further
the voltage, the contact tip will burn.
C) In any case, an excessive wire speed can be corrected through the arc voltage increase. The limit of this operation depends on the thickness
of the material to weld (a certian limit exceeded will result in the perforation).
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Position the torch over the seam to be welded holding it at approximately a 45° angle with the nozzle at 5 - 10mm. Lower the shielding helmet
and press the welding torch trigger to initiate an arc. As the weld is deposited, push the torch from a left to right direction, slowly along the seam
at a constant speed.
Using the wire feed speed control potentiometer, adjust for a "crisp" sounding arc.
As time goes by it will be possible to reach a certain sensitivity to the sound produced by the arc allowing to get a more and
more precise adjustment of the welding parameters.
10.0 ALUMINIUM WELDING
The machine will be set up as for mild steel except for the following changes:
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100% ARGON as welding protective gas.
Ensure that your torch is set up for aluminium welding:
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The lenght of the torch cable should not exceed 3m (it is advisable not to use longer torches).
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Install a teflon wire liner (follow the instructions for the renewing of the wire liner at paragraph 6).
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Ensure that drive rolls are suitable for aluminium wire.
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Use contact tips that are suitable for aluminium wire and make sure that the diameter of the contact tip hole corresponds to the wire diameter
that is going to be used.
11.0 WIRE SIZE SPECIFICATION CHART
Reference Fig.6
1
2
7
6 4
5
1
2
3
4
5
6
7
14
3
Wire Diameter (mm)
0.6
0.6
0.6 - 0.8
0.6 - 0.8
0.8
0.8
1.0
Wire Feed Speed Adjustment
LOW
LOW
MEDIUM
MEDIUM
MEDIUM - HIGH
HIGH
HIGH