Fanny-Yi Wan

Robots confine hazards

It may seem paradoxical at first, that a country such as China with its relatively low labor costs should be a robotics market. Robots, however, can work in environments that are too hazardous for people and will achieve an accuracy and reproducibility beyond that of humans. The following two examples show robots at work in two totally different environments. In the first article, robots are seen painting consumer electronics enclosures. Such items as mobile phones, laptops or electronic piano keyboards are produced in very large numbers. By carefully optimizing workflow, waste of paint and sub-standard paintwork can practically be eliminated. In the second example, metal enclosures are welded. The hazards of a laser welding environment, and the precision required of the welding make robots the natural choice also in this application. Painting robots The realization of Flextronics Zhu Hai’s Painting Shop for Dell laptop covers is undoubtedly the biggest challenge and the most successful implementation that the company’s manufacturing industry department has ever experienced. With its headquarters in Singapore, Flextronics is the world’s leading electronics manufacturing services provider. It is focused on delivering innovative design and manufacturing services to technology companies. With a revenue of US$ 14.5 billion in the fiscal year 2004, Flextronics is a major player in global technology manufacturing. It provides assistance to electronics manufacturers by supporting design, building, shipping and service processes. Flextronics has facilities in 32 countries on five continents. In expectation of the increasing production of laptops, Flextronics Enclosure (Zhu Hai) signed two contracts with ABB to supply 14 painting robots1(See margin image: An ABB painting robot for Flextronics) forming seven lines for its Dell laptop cover painting shop. An ultra-clean environment The paint shop is separated into two portions: a loading/unloading area with normal air conditioning and a painting area with a class 100 K1) clean room. All cast deflashing zones2), ovens and cooling zones are on the second floor. The air contamination at the process equipment reaches class 10K. The most significant items of the supply contract concerned robots, spray booths, air conditioning devices, ovens and conveyors. Because of the unique strengths of ABB’s robots, the robot contracts were secured in a highly competitive market environment. ABB’s advantages include the robots’ advanced handling capability, their proven operational flexibility and robustness and the advanced professional simulation software – Robot Studio, which accompanied the delivery. Further strengths include conveyor tracking, paint saving technology, short delivery time and a competitive price. Besides the strengths of ABB’s robots, the ingredients of success were embodied in the experienced team leaders and design engineers. The main requirements for automated manufacturing are higher productivity at lower cost, environmental compliance, increased flexibility and shorter execution cycles. Besides the strengths of ABB’s robots, the ingredients of success were embodied in the experienced team leaders and design engineers: The people who endow those cold robots with soul and power. Painting the way for future This pioneering success helped build a healthy mutual partnership, leading to Flextronics intention of purchasing further ABB painting robots in the following 2 years. These include the paint shop for Casio electronic piano keyboards in Dong Guang and the paint shop for Sony Ericsson mobile phone covers in Malaysia. 2 A high precision laser welder at work Mr. J.D. Yang, Quality Manager at ComPal, Flextronics’ Kun Shan plant says, “We believe this is the beginning of a long lasting good relationship between ABB and ComPal. We are part of the same value chain and form a most competitive team”. Welding robots A customer in China uses a robot laser welding system for manufacturing several types of stainless steel boxes 3. The requirements placed on the welding equipment are very high because no oxygen may leak into the boxes. The flexibility of ABB’s robots and the precise coordination made possible due to the IRC5 controller made ABB the natural partner for this high-precision job3). Safety first! The light from such a powerful source as a welding laser diode can cause permanent blindness. Hence, greatest care is taken to ensure the safety of staff at all times. Even reflected light is hazardous; with this in mind, the cell 3 is uncompromisingly implemented to eliminate risk of contact. The enclosure is made of multiple layers of sheet metal supported by a steel frame. According to risk-analysis recommendations, various sections may be additionally reinforced. 3 The laser can cause blindness – the cell is totally enclosed. Robust automatic doors are provided for work-pieces to enter and leave the cell. Additionally, a service door is provided for staff to access the cell. A safety mechanism monitors these openings and ensures welding cannot take place while any door is not completely shut and locked. Any attempt to open a door during operation stops the process instantly. The uptime conundrum Another major challenge in robot welding is mastering the uptime of the welding laser. The efficiency of an Nd: YAG (neodymium yttrium aluminum garnet) laser source is limited to around 2–3 %. To offset the low laser efficiency, the technology must strive for the highest possible productive laser uptime. This is achieved using a mirror that switches the ray between cells: ideally, one cell starts welding the moment the other cell stops – and the light is never wasted! The new IRC5 industrial robot controller provides unparalleled capabilities with its MultiMove functionality4). This not only precisely synchronizes multiple robots or positioners with extreme accuracy, but also controls the mirror that switches the ray, ensuring that this perfectly matches the movements of the robot. The welding laser used is stationary, and the light led to the seam by flexible fibre optic lasers. This saves on time-consuming alignment and adjustment work when the welding source is changed. Seam tracking In Seam Tracking, the robot “sees” and follows the intended welding seam using a focus optic. This optic is the same that is used to focus the main welding beam (Beam Path Integrated Vision). The lack of additional camera optics leads to a compact tool design. Seam tracking is supported by powerful software that analyzes the pictures fed to it by the camera and adjusts the spot position accordingly. A cycle time of about 40 ms leads to an exceptional responsiveness. A roller positions the welding tool on the seam line and presses the two pieces of metal together at a defined pressure to assure optimal bonding. The pressure is pneumatically regulated and adjustable. The roller angle is fixed but the optics tilt to follow the contours of the workpiece. Filler wire, protective gas nozzle, welding beam focusing unit and workpiece sensor are all attached to this press device module, assuring they are always in the intended positions, and that they all ”float” along the seam together. The application The robot cell4 contains two welding stations. Each has its own door for loading and unloading work-pieces4a 4b. A welding robot is located between the stations 4cand can access either station through door-protected openings in the walls of the workstation 4d 4e. 4 A look inside the cell of 3 Seam tracking is supported by powerful software that analyzes the pictures fed to it by the camera and adjusts the spot position accordingly. A cycle time of about 40 ms leads to an exceptional responsiveness. In one station, the boxes are welded 4f. To assist this process, an adjustable positioner orients the workpiece 4g. While this station is being loaded or unloaded, the robot switches to the other station 4h, where other assembly parts and fastening elements are laser welded. Using this technique, complete subassemblies can be laser welded, providing savings in assembly work and logistics. The laser beam from a single 3300 W diode pumped Nd: YAG laser is guided through a flexible optical fiber to the welding tool. The laser output is switched between the stations in the cell, so making optimal use of laser uptime, and accomplishing two tasks in a single work cycle. The cell is equipped with a Permanova WT03 Laser Welding Tool and an ABB robot. The system uses Seam Tracking technology and the AW hybrid-welding feature with a MIG power source. Using a laser for welding assures tight seams while causing very little heat deformation. It also only requires access from one side, so reducing handling requirements. Fanny-Yi Wan ABB China Ltd. Shanghai, China fanny-yi.wan@cn.abb.com Footnotes: 1) Class 100K is a classification of air contamination in a clean room according to US Federal Standard 209E. Class 100K indicates that there are no more than 100, 000 particles larger than 0.5 micron per cubic foot of atmosphere. For class 10K this reduces to 10, 000 particles. 2) Deflashing is the process of removing flash, the excess material that casting leaves on a cast item. 3) The laser welding story uses material from “Welding sees the light” by Fabrice Legeleux, ABB Review Special Report Robotics (2005), pp20–22. 4) See also „Team-mates“ by Christina Bredin, ABB Review 1/2005 pp 26–29.