Neither work well. Too low an amperage and you never get good
penetration, giving you a bead that sits on top of the base metal. Too
high an amperage and you blast right through the base metal. To slow a
wire feed and you get the pop-pop-pop as the wire burns back. To fast a
wire feed and you get excess weld buildup (looks very similar to low
amperage btw). And if you move the gun along too fast you never get
good penetration, and a stringy looking weld to boot. Move the gun too
slowly and you tend to burn through, get a lot of weld wire buildup and
a wide bead.
I personally am a hot welder. I tend to crank up the amperage and wire
feed, and move along quickly. You need to balance all three. Some are
faster then me, some are slower. All are good if the three things are
properly balanced.
Sheet metal welding is hard, don't let anyone kid you otherwise. I'd
suggest you start practicing on much heavier stock, like 1/4" angle
iron. A heavy base metal is very forgiving, and will let you learn how
to balance the three settings (amperage, wire feed, gun motion).
A relatively simply way to set things up with MIG is to first set at
the lowest amperage and reduce wire feed to a minimum. You want the
wire to be burning back going pop-pop-pop. This way you know you are
too slow on wire feed. Now gradually increase it until the pop-pop-pop
stops, and you get a steady zzzzzzz sizzle. At this point, your wire
feed roughly matches your arc amperage. This works for all settings
btw, though I've got you started on the lowest.
Now that you've got wire feed matching amperage, lay a bead.
Preferably on that heavy practice stock I mentioned. You'll find that
you're moving slowly because the puddle is small and it's not melting
with enthusiasm. Practice until you get a reasonable looking bead,
albet small.
Crank up the power. The gun will immediately start the pop-pop-pop
again, and you will have to increase wire feed. Run another bead.
You'll find yourself going faster now. The puddle will also be larger
and the weld will look better.
Keep on cranking up the power and wire feed on your practice piece.
Once you get up rather high, you will notice you can burn through if you
go too slowly. This is about as high a power&wire feed setting as you
can go at a given skill level. The better you become, the hotter you
can handle it.
Now, and only now, would I suggest starting the practice all over again
with thinner metal, and I don't mean sheet metal yet. When you get to
the sheet metal, you'll find that it's very easy to burn through while
making a good bead, but you'll have the necessary experience from the
previous heavier stock to know how to increase your movement of the gun
and balance it.
>>> "Larry Vaughan" <lvaughan@pldi.net> 08/29/02 09:15PM >>>
What works best on sheet metal, a fast pass with hi setting or slow
pass with low setting?
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