Case Study

Case Study: Assembling Walls for Prefabricated Homes
Application: Assembly, material handling
Robot Model: Kawasaki BX250L large payload robots

OVERVIEWSOLUTION

Prefabricated homes have recently grown in affordability.
This growth has led to increased demand for homes that canbe manufactured quickly and inexpensively and assembled
on-site. However, that affordability translates to thinner
margins for building component manufacturers, especiallywhen they are bidding against each other for the same
projects. As many in the industry have learned, the more
automated their manufacturing process, the morecompetitive they become at the bidding table.

• Four Kawasaki BX250L robots mounted to Güdel
TrackMotion Floor-3 rails

Builder Rehkemper &amp; Son contacted Kawasaki
integrator SCADAwareto help automate their prefabricatedhome assembly process. In addition to sharpening theircompetitive edge, they also wanted to minimize theirreliance on human labor due to shortages and lapses inproduction. After reviewing Rehkemper’s manual processes,
SCADAware designed a one-of-a-kind system for automatingmuch of the prefabricated wall assembly process usingcustom software, Kawasaki robots and Güdel rails.

• Robots mount cumbersome OSB panels to wall frames
and carve windows and doors into panels• Custom SCADAware software outlines cuts for robots
Factory assembly of prefabricated homes is done in twostages. First, wooden studs and beams are sawn andassembled to form the skeletal walls, roof, and floor trusses.
The next phase involves applying OSB sheathing to
pre-framed walls, nailing the panels to the framework, andcarving out holes for windows and doors. The component
parts are then shipped to the building site, where they areassembled into a standing structure.

CHALLENGES
Cumbersome material, high precision application
In Rehkemper’s process, oriented strand board (OSB)
sheathing is adhered to the prefabricated walls. OSB comesin large, heavy, pressed-wood panels that can be difficult tomaneuver. They needed a robotic solution that could
accurately place nails to affix the boards to the wooden
studs and beams hidden underneath. What made this task
so difficult is that, compared to other building materials,
wood is notoriously imprecise.
“Wooden boards are often warped; and once you lay OSB
down, you can no longer see the where the stud is located.
If the nail only holds air, then we’re in trouble,” says Rick
Caldwell, president of SCADAware.

The Kawasaki BX250L robot can lift 250 kg, and offers a through-arm cable
design for added convenience.

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SCADAware engineers wrote custom software that looks at
the electronic version of the design of the wall and shows
the robot where to nail and cut. The system employs alarge, adjustable, motorized table to accommodate framedwalls measuring 8 – 14’ high and up to 20’ wide. Single
walls are conveyed onto SCADAware’s table, where they
are squared against a fixed end stop at the far end. The
table’s adjustable edges come together to align the frame
top to bottom.
This ensures the wooden stud nearest the end stop isstraight with its physical centerline aligned to within
1/16th of an inch or better of the digital design. There areservo-controlled fingers under the wall to straighten any
warped studs. These fingers help align the next 3 studs bysliding up the table’s central rail and applying pressure tostraighten each stud.
Meanwhile, two pairs of Kawasaki BX250L robots – eachwith a reach extending 2,812 millimeters, or just over 9feet – are mounted on corresponding Güdel TrackMotion
Floor-3 (TMF-3) units extending the length of the table oneither side. Each Güdel track measures 15 meters anddelivers a 12-meter working stroke, allowing all four robots
to work together along the entire length of the table.
After the wall is in place, one of the rear robots next to theconveyor uses vacuum heads to pick up a 4 x 8-foot OSB
panel and place it over the now straightened studs. Oncethe first panel is fully attached, the robots and fingers
repeat the process until the wall is completely sheathed.
All four robots can easily switch tooling. As one set ofrobots carves windows and doors into the OSB panel, theother two remove the cut sheathing and transfer it to thescrap heap.
Robots = Reliability
Rehkemper’s process is extremely labor intensive, which
made it difficult to find and retain employees. Automation
can be the perfect solution for these situations, asmanufacturers can rely on them to work consistently.
Kawasaki robots are known for their reliability andflexibility. Offering a 250 kg payload, Kawasaki BX250L
robots can easily lift large, cumbersome OSB walls withease. Their patented hollow-arm structure provides easy
installation, maintenance and minimized wear. Theirextended reach, high speeds and advanced motion control
technology reduce cycle times.

Kawasaki Robotics (USA), Inc.
Corporate Headquarters for Americas
28140 Lakeview Drive, Wixom, MI 48393, U.S.A.
Phone: +1-248-446-4100 Fax: +1-248-446-4200

Kawasaki robots are used to mount cumbersome OSB sheeting to pre-framedwalls and cut out windows and doors.

RESULTS• Efficiency drastically increased• Throughput increased by at least 25%• Labor costs reduced
In simulations, the system has shown it can finish assemblyof an 8 x 20’ wall in considerably less time than it would
typically take two operators to complete — including
placing and affixing OSB sheathing and cutting it to form
windows and doors. With additional optimization, Caldwell
believes the system can do even better.
“A big impetus behind Rehkemper reaching out to us was
the difficulty they were having in hiring workers to dothese sorts of jobs,” said Caldwell. “But our collective goal
was also to help them to compete better and get the job
done quicker for less of a cost.”
The speed, versatility, and precision enabled by Güdel’s rail
promises to increase throughput by at least 25% with noloss in quality. The improved productivity and reduced
labor costs enable contractors like Rehkemper and Son tosave money and offer more competitive bids. Currently thetrack and robot system has increased the linear footage
produced each day by 25% with no loss in quality; furtheradjustments are expected to increase efficiency to 35-40%.
An additional benefit is the removal of human labor
resulting in less downtime, more precision, and no injuries.

KawasakiRobotics.com