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9-3.
GAS
METAL
ARC
WELDING
(GMAW)-SPOT
Instead
of
having
a
continuous
or
pulsed
weld
to
join
two
pieces
of
sheet
steel
together,
welding
in
spot
of
1
to
1-1/2
inches
(25-38
mm)
apart
can
be
done.
The
MIG
spot
welding
process
fuses
two
pieces
of
sheet
steel
to
gether
by
penetrating
entirely
through
one
of
the
pieces
into
the
other.
The
spot
process
is
designed
to
be
used
in
any
position.
Little
joint
preparation
is
required
other
than
cleaning
the
surfaces
and
ensuring
that
the
two
pieces
overlap.
Spot
welding
is
based
on
the
same
principles
as
continu
ous
seam
welding
except
that
there
is
no
travel
speed
in
volved;
instead,
there
is
a
welding
time
interval.
The
weld
is
made
by
placing
the
welding
gun
directly
on
the
top
sheet
and
holding
it
motionless
as
shown
in
Figure
9-8.
When
the
gun
trigger
is
depressed,
the
electrode
wire
and
shielding
gas
will
be
continuously
fed.
The
arc
will
be
maintained
for
the
full
length
of
time
set
on
the
SPOT
TIME/PULSE
ON
TIME
control
and
it
will
con
tinue
to
penetrate
in
one
place
until
the
top
sheet
is
welded
with
the
bottom
sheet.
After
the
preset
welding
time
has
elapsed
the
wire
will
stop
feeding,
the
contactor
will
open
and
the
arc
will
be
broken.
The
GMAW
spot
welding
process
produces
little
heat,
therefore
little
distortion
results.
Because
of
the
low
heat
characteristics
of
this
technique,
it
is
often
used
when
welds
are
made
in
close
proximity
to
upholstery,
rubber,
or
other
flammable
materials.
Figure
9-8.
Fender
Repair
With
Spot
Nozzle
Figure
9-7.
Spot
Weld
OM-113
336
Page
36