AFRICAN FUSION—MARCH2014
31
Automation for aluminium stage trusses
locating blocks and pneumatic clamps
to hold the truss sections and cross
bracesaccurately inplace. “All parts for
the jigweremadeon thepremisesusing
thecompany’sownCNCmachines,”he
informs
African Fusion.
To avoid having tomachine curved
fit-up geometries into the cross brac-
ing, a flattened tube section has been
chosen. “Thisallowsus toprecisioncut
the cross bracing at a 45° angle and
align them to the centre of the upright
columns. Straight fillet welds are then
used to join each cross brace to the
centre of the uprights.”
At the starting point of the process,
two parallel ‘ladders’ are laid out on
the jig tablewitha squarebaseplateat
eachend. Thecrossbracesare inserted
into the locating blocks and the pneu-
matic clamps activated. At the push
of as single button, the robot welding
system then systematically places a
straight fillet on each upper joint of the
ladders, with the robot moving up on
its track to access all the joints along
the length of the truss.
Using the pulsed synergic capabil-
ity of the Fronius power source, each
weld starts with a short slope-in and
finishes with a slope-out sequence to
partially fill the crater. “In the end, we
didn’t need to use theCMTprocess, as
the tube section is relatively thick and
doesn’t need to be kept cold, but the
synergic pulse feature is ideal for the
aestheticappearanceweneed,”Kruger
explains.
Then, in the same jig, we box up
these two ladders and insert another
set of cross braces. The joints on the
inside surface iswelded, thewholebox
truss is turnedand the final set of cross
braces is welded into place. “At this
point, theweldinghas been completed
ononly four of theeight sidesof thebox
truss. So the truss is transferred to a
rotatingpositioner on the opposite side
of the robot. This allows access to the
other four sides,whichare then
systematically welded to
complete the fabrication
process,” says Kruger.
With a production
capacity from a sin-
gle system of some
60m of completed
truss per 12 hour
shift, Kruger sees
opportunities to
replicate this sys-
tem to increase
productionatwill.
“And production
is not limited by
the robot system.
Each of the truss
componentsarepre-
cisionparts that need
to be CNC machined
before each truss can be
assembledandwelded,”he
The truss is then transferred to a rotating positioner on the opposite side of the robot. This allows access to the other
four sides, which are then systematically welded to complete the fabrication process.
Stage Plus Engineering
manufactures aluminium
stage trusses for the
entertainment industry.
points out.
With no seam tracking and relying
onlyon theaccuracyof theparts, the jig
and thepathprogram, the reject rate is
less than2-3% “and the rejects seldom
haveanything todowith the robot. It is
almost always due to a gas or welding
wire problem or a fit-up error”.
These locally produced trusses,
although only launched last year, have
alreadybeenusedat the Johannesburg
Motor show and “our customer was
very happy.
“We are positioning to be
a distributor andmanufac-
turer of choice for the
wholeAfrica,”Barnard.
“And automation is a
driver for achieving
that. It allows us to
be very competi-
tive againstWest-
ern and Eastern
Europeanmanu-
facturers. “We
are determined
to become glob-
al player, so our
next step is tobe-
come internation-
allyaccredited,”he
concludes.
