Plug Welds; Skip Welding; Troubleshooting - Miller Electric AUTO ARC MW 4150 Owner's Manual

9-4.
PLUG WELDS
Plug welds provide
a means
of
joining
two
pieces of
metal where the thickness of the
top sheet is beyond the
normal range of the
welding
power
source or
where
sheet metal sections
are
too thin to
be
spot
welded
or
pulsed welded without producing distortion
or
burn
throughs. The
plug
weld is made
by drilling
or
punching
a
hole
in
the top sheet, clamping the metal sections
tightly
together,
and
filling the hole with
a
weldment. The
plug
weld
can
be timed
using
the
spot timer
or
untimed. Plug
welds should be
spaced
1 to 1-1/2
inches (25-38 mm)
apart.
Plug welds
on
sample materials should be made
so
that
proper
parameters
can
be set.
9-5.
SKIP WELDING
Skip welding provides
a means
of
making
a
series of
short welds, usually less than
3/4 in.,
(18 mm) in length
each, consistent in size and appearance. Skip welding
can
be accomplished
with this unit by setting
a
spot
weld
time and jogging the
gun
trigger
off and
on
again each
time the
spot
timer times out.
Skip welds
on
sample
material should be made
so
that
proper
parameters
can
be set.
9-6.
TROUBLESHOOTING THE GAS METAL ARC
WELDING PROCESS
A. Porosity
Figure 9-9. Porosity
Remove spatter
from the gun nozzle.
Check gas hoses for leaks.
Eliminate drafts (from fans,
open
doors, etc.) blowing
into the
welding
arc.
Place nozzle
1/4
to
5/16 in. (6-8 mm) from workpiece.
Increase
gas
flow
to
displace
all air from the weld
zone.
Decrease excessive gas flow
to
avoid turbulence and the
en
trapment
of air in the
weld
zone.
Hold gun
at
end of weld until molten metal solidifies.
Check for frozen C02
regulator/flowmeter.
2. Wrong
gas.
Use
welding grade shielding
gas.
3.
Dirty welding
wire. Use clean and dry welding wire.
Eliminate pick
up of oil
or
lubricant
on
welding wire from feeder
or
conduit.
4.
Workpiece dirty. Remove all
grease,
oil, moisture, rust,
paint, undercoating, and
dirt from work surface before
welding.
Use
a more
highly deoxidizing welding wire.
5. Welding wire extends too far
out
of nozzle. Welding
wire should extend 1/4
in.
(6 mm) out
of nozzle.
Possible Causes
1. Inadequate shielding
gas coverage.
Corrective Actions
OM-113 336
Page 37