The Shed – September-October 2019

9. Listen for a smooth arc sound, often
   referred to as bacon frying — you’ll
   know the sound.


10. Change your torch angles so that you
    can gauge for yourself the different
    effects that it can have on bead
    shapes.

Wire

To set up the machine with the correct

wire, feed the wire from the roll through

the wire guide over the roller. Make sure

that the roller matches your wire size

and the wire type:

• V-groove roller for hard wire


• knurled roller for gasless.
  Clamp the roller and apply tension that
  you can just feel to avoid over-tightening.
  I like to take the tension off completely
  and slowly wind the tensioner down. Use
  the feed button to feed the wire through
  the torch cable. It may help to remove the
  nozzle and the contact tip to ensure that
  the wire is feeding.

Wire-feed speed

Adjust the wire-feed speed using the wire-

feed control on the wire feeder. Set to the

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that came with your machine. Amperage

depends on the wire-feed speed. The

higher the amperage the faster the wire

speed. If in doubt always start with the

settings in the middle of the range.

MIG machines that have a synergic

mode or setting are a blessing for

learners. ‘Synergic’ means that the amp

and volt settings are calibrated together

into one control knob. Basically as you

increase your wire speed / amps, the

volts will change automatically to suit.

This takes the trial and error out of

MIG welding. I have come across many

novices who can weld beautifully once

things are set right.

Voltage

Adjust the voltage to the suggested

procedures in the handbook. If the

wire is burning off too quickly and is

making a soft molten sound, the voltage

is probably too high. On the other

hand, an excessively convex or ropey

bead (accompanied by a large amount

of spatter) indicates that the voltage

is too low, so correct it by increasing

the voltage. Check your earth-cable

connections. When using gas-shielded

MIG set-ups you actually have quite a

wide voltage window which can still

produce satisfactory results, albeit a bit

more spatter here or there. f

art d

Porosity

Porosity in gasless wire is a

common fault but easy to avoid. To

eliminate porosity:

• clean the parent metal of
  moisture, oil, paint, and rust


• decrease your voltage: the arc
  may feel hot and smooth but
  too high a voltage is the most
  common fault


• increase stick-out: short stick-
  out raises the arc voltage


• increase wire-feed speed


• 
  

MIG liner tubes: Teflon (top) and steel

Adjusting the tension

Gas regulator

The ear-ometer test

Earth clamp

Comparison of a good weld (below) with a porous one. Note how deep the porosity runs