Robotics Case Studies
Shell Solar Implements Robotics to Increase Productivity
FANUC America Corporation Posted 01/27/2005
Fossil fuels giant Shell Oil Company investing in solar energy? To most people, the two mix about as well as oil and water. After all, the Shell brand brings to mind a company with a strong heritage of sprawling oil refineries, chemical plants, offshore drilling platforms and of course, thousands of retail gasoline stations. But drill a little deeper, and you will discover that Shell is also a big player committed to renewable energy and is in fact, among the largest manufacturers and marketers of solar photovoltaic panels in the world.
To give some background, ‘‘photovoltaics’‘ are solar cells that absorb sunlight and convert it directly into electricity. Solar cells are very thin wafers, typically made of silicon. A number of cells connected together form a module or a module array. The more modules, the more electricity you can produce. For most homes or businesses connected to their utility grid that have solar modules on their roof or ground-mounted, excess power produced by the panels flows back into the power lines for use elsewhere. So homeowners and businesses alike can produce clean energy, help the environment, and enjoy the financial benefit their solar electric system brings.
In order to maintain Shell’s leadership in solar manufacturing, Eric Culberson, the Automation project manager of Shell Solar Industries USA plant in Camarillo, CA, was recently tasked with resolving a challenge common to many facilities. He needed to lower direct labor costs, which specifically meant that he had to reduce manual handling of the solar panels, which weigh up to 40 lbs. And like many Automation Engineers, Culberson thought he would not only have to reduce staff, but also increase productivity and still deliver a quality product in a shorter amount of time.
‘‘Our production line consisted of manually operated processing stations which required people to move the product from station to station,’‘ says Culberson. ‘‘The line was highly operator dependant and the output varied directly during a 12 hour shift. If an operator were missing from one station, the complete line would shut down. Of course, it would completely stop during breaks and lunches because all stations had to be manned in order to run.’‘ Competitive pressures and increased demand for the panels eventually dictated that the time for a major re-evaluation of the production system had come. In particular, two bottleneck processes needed immediate attention: Lay-Up and Framing. But where to begin?
Shell’s engineering staff studied a number of possible implementations, including an internal engineering solution, but ultimately decided to award the bid to FANUC Robotics’ regional office near Los Angeles, CA. ‘‘We selected FANUC Robotics because of their service and support capabilities, and on the strength of their product line,’‘ Culberson explains. The contract was for complete turnkey system responsibility: engineering, floor layout, procurement, robots, controls, software, end-effectors, installation, and final approval run-off.
The Lay-Up workcell comprises two lines, which handle electrically conductive strings and materials to form the circuitry and uncured laminates. This was originally a very labor-intensive 24/7 operation. FANUC Robotics’ M-16iB and S-430i robots were selected for their man-size reach, their precise motion, and their ability to perform a wide variety of tasks. Four were deployed per line.
Using multi-purpose end-effectors, the pair of robots at the head of the lines picks up the strings, papers, glass sheets, and plastic sheets of different sizes to very precisely perform the assembly process. Proper placement of the strings is a critical step for the solar panel’s proper operation. The M-16iB’s ability to repeatedly move to the same position time after time guarantees string placement within a remarkable 70 thousandths of an inch. String placement outside of +/-30 thousandths tolerance would potentially result in a short circuit.
Other M-16iB robots work on opposite sides of the laminate. They pick up interconnect buss bars and place them on a circuit assembly table, and then pick up spot welders and weld the buss bars to the interconnect ribbons at two points per string. They then trim any excess ribbon after welding and return the spot welders to their holders.
The remaining robot tapes the ends of the solar cells to prevent them from touching during the lamination process, and a large S-430i robot places the completed circuits on the outfeed conveyor.
‘‘The original method required six people for each of the two lines and produced only three parts every 16 minutes. Changeover took 4 – 8 hours,’‘ says Culberson. ‘‘Now, we’re producing three laminates every eight minutes with minimal manual intervention. Changeover between the seven product types takes less than an hour.’‘
The other major workcell that needed to be re-engineered was a Framing workstation; the processes by which the frame and junction box with bypass diodes are installed. Four FANUC S-series robots were chosen for their large reach, 120kg payload capacity, and their precise positioning capability.
The taping robot takes trimmed laminates from one of two infeed conveyors and tapes their edges by running them through a taping machine. The S-430i robot then dips the edges of the laminates into a water tank in preparation for framing, before placement in a precision framing table.
Another FANUC S-430i robot picks up four frame components and places them into the framing table, retrieves a screw gun, and drives eight screws into the frames at a specified torque. The first robot returns and picks up the framed modules and places them on the outfeed conveyor for further processing.
At this point, the M-16iB weld robot finds the endpoint of one of four buss bar leads on the back of the module, determines its position, bends the four leads to 60 degrees and removes the traveler card underneath. The weld robot communicates the variable coordinates to the last M-16iB robot before it places the junction box over the leads.
Simultaneously, the dispense robot picks up a junction box from one of six conveyor locations and applies RTV sealant to the back of the box. Precise location and volume of the RTV bead are essential to ensure a proper seal during the 25-year warranty period for the panel. When dispensing is complete, the same robot places the junction box on the module and the weld robot returns to weld four leads to the terminals on the junction box. After assembly is completed, the modules are conveyed for electrical tests.
Comparing before and after, ‘‘In Framing, the robots are delivering a substantial reduction in labor costs,’‘ says Culberson. ‘‘Also, the cell can run two different products simultaneously, while the manual line could not. All products are run via software set-ups that are stored in the control system, so only a few minutes downtime for product changes is required.’‘
Initially, some of the employees were skeptical of the robots’ ability to perform the variety of complex tasks. Their skepticism was quickly allayed once production began. The employees understand the role that the robots play in keeping their plant cost-competitive while producing quality solar panels used around the world.
Key success criteria for both Lay-Up and Framing were uptime and payback. Culberson reports that uptime for both workcells went from about 80% to about 95%, with the robots themselves up virtually 100% of the time. Payback for Lay-Up was achieved in under a year, while Framing took about 18 months.
Having exceeded these and other productivity targets, Shell Solar is automating, with robots, the remaining manual operations. They are deploying additional robots to perform the QA testing functions and supplementary trimming operation. Two years ago, the plant had zero robots in their module manufacturing area. Now, at the end of 2004, they have 16. Shell Solar has certainly shown their commitment to the solar business by their investment in automation. For more information on Shell Solar, visit www.shell.com/solar or call 1-800-94-SOLAR.