Easton, Ill.-based Onken’s Inc. is a maker of patented bulk grease-collection
systems, trailers, bins, and oil storage tanks for such customers as auto parts
retailers, restaurants, and the U.S. government. The tanks vary in capacity from
120 to 500 gal.
Since 1983 the company employed a team of welders to manufacture its leak-proof products. Five manual welders worked 10-hour shifts to manufacture 10
tanks per day. But according to J.R. Onken, operations manager, the company
has had difficulty finding quality welders.
“We saw a future where there were no longer enough welders for us to stay
in business,” he said. “Our tanks are UL-approved to withstand a 5-PSI air and
leak test. Every welder you interview says they can weld, until they have to weld
something that doesn’t leak. That’s a level of expertise not everyone has.”
Onken began researching options for automating its tank production. A ro-
botic welding cell was considered, but some of the management team hesitated
since the company had no previous robot experience. The decision was put on
hold, but Onken continued to lobby for a robotic automation system.
As the welder shortage became increasingly acute, Onken took up the discussion with robotics manufacturer Yaskawa Motoman. Yaskawa Motoman visited
Onken’s to complete a detailed audit of the weldment and of the manufacturing
methods used to produce the components.
Robotic welding cell helps tank manufacturer bridge welding skills gap
The audit indicated that this was not an easy weldment to automate, especially for a new robot user. Because of the design of the tank, the weld joint
would not be repeatable enough for standard robotic welding. Advanced technology, such as seam finding with laser-based and through-arc seam tracking,
would need to be implemented. While this robotic welding technology is robust
and very reliable, it takes a training commitment from the end user. The management team at Onken’s agreed to implement the required training recommended by Yaskawa Motoman.
The company chose a simple, flexible, two-zone robotic workcell with an
extended-reach Motoman® MH50-20 robot. The robot is designed for processing large parts like Onken’s tanks. The required fixturing to secure the tanks for
welding was provided by the tank maker.
The workcell design allows operators to load five different tank sizes for welding. The company’s typical batch production approach uses both zones to weld
the same tank size. Based on order demands, the workcell has the flexibility to
produce different tank sizes. For instance, a 120-gal. tank can be welded in zone
one, and a 500-gal. tank can be welded in zone two.
The two-zone workcell allows the operator to unload a welded tank and reload in one zone while the robot is welding in the other zone. Light curtains in
the safety zones and roll-down safety barrier curtains on each side of the robot
safeguard the operators during part load/unload. Arc flash curtains surround
the workcell for additional safeguarding.
While the system is designed for simplicity, advanced technology helps locate and track the various types of weld joints. Since the tank is rolled into the
zone and roughly placed by operators, a Servo-Robot camera is used to identify the weld joint and orientation, which initiates the proper weld program. As
the robot welds the joints, which include contoured rolled corners, the camera
provides real-time seam finding and tracking just ahead of the weld torch. This
enables the robot to alter its path to keep the weld puddle in the proper location
on the weld joint.
Once the tank seams are welded, traditional touch sensing locates a large
circular flange and several smaller threaded couplings on the top of the tank.
Once each component is located, ComArc through-arc seam tracking is used to
enable the robot to alter its path and keep the weld puddle in the seam of the
weld joint. Through-arc tracking of these welds is required because of distortion
during the weld process and the overall manufacturing tolerances of the tanks.
The use of this technology has resulted in high-quality welding, ensuring that
the tanks are sealed and meet overall quality standards, and reduced potential
“With the fittings that we have for the tool end of the robot, the
Yaskawa America Inc.,
system weaves and sees the arc voltage. The robot will even weld
around circles if need be,” said Onken. “We sent one of our welders
to Yaskawa Motoman for a week’s worth of training, plus we had one
of their employees on-site with us for additional training. Within a
couple months, our welder was proficient with the cell.”
The robotic welding cell has removed up to 20 hours from the pro-
duction process of manufacturing 10 tanks daily. Production sched-
ules now are maintained with three welders on a 10-hour shift. The
two additional welders are now available to take on other projects,
which has reduced the company’s need for contract welders, result-
ing in further cost savings.
Motoman Robotics Division
100 Automation Way
Miamisburg, OH 45342