Omron safety controller makes 'light' work at solar panel manufacturerSpain enjoys more hours of sunshine than almost any other European country, so it's hardly surprising that it is one of the leaders in the development, manufacture and installation of photovoltaic energy systems. These generate electricity from sunlight, using solar panels of photovoltaic cells, and are increasingly used as a source of renewable energy, especially for newly built houses, offices and factories.
Helios Energy Europe (Heliene) is one of Spain's leading manufacturers of high-power (200W to 250W) photovoltaic modules, which are used mainly by industrial companies and for generating electricity on a commercial scale. The company has a reputation for making high quality and innovative products that are both efficient and competitively priced. To a large extent, Heliene's reputation derives from its customised production lines which are highly automated to optimise productivity.
The solar panels are made up of 156mm square cells, which are precisely positioned and linked in 6 x 10 arrays with short ribbons of copper. These are precisely positioned on to a glass panel and soldered together, before the panel is laminated at temperatures of 150°C. The laminated panels must have all air removed from between the layers, as this would adversely affect the energy generating performance. The final stage is to assemble the panels into aluminium frames before they are tested in a solar simulation to make sure that they meet the required standards.
The whole process is carried out using a line of robots, with very little human intervention apart from basic machine operation, visual inspection and some cleaning of the products as they move down the line. The need for precision is paramount, because once the panels are laminated, it is almost impossible to rectify any defects. In addition, safety is a key consideration, and the delicate - and expensive - materials must be handled with extreme care to avoid damage, or injury to the trained staff who work on the line.
Advanced safety system
Whilst the deployment of robotics for automated and precise handling of the solar panels is essential to the process, this does raise many issues in regard to operator safety. The entire line has numerous robotic stations, with access points for operators and product transition. Each of these areas requires guarding by means of a safety light grid or mechanical guards with safety interlocks. Omron's CLIC range of safety light curtains was used due to their flexible muting control, which allowed fluid product transition, without operator interaction.
With the sheer number of safety sensors and machine guard interlocks, as well as numerous emergency stop buttons located around each machine area, using a conventional relay based safety control system would have been a wiring disaster. As well as the complexity of the wiring, the time to install and number of relays required would mean that the cost of the safety system would have escalated. After consultation with Omron, a decision was reached to design the safety system based on Omron's NE1A safety network controller. Using a networked based safety system offered engineers some key advantages. Reduced wiring using distributed local I/O modules, which allowed I/O points to be located in the vicinity of safety devices, eliminating long wire runs back to the main control panel.
In addition, the networked I/O modules run on a safe DeviceNet field bus, allowing connection between the modules on a single cable. As well as aiding the installation process, the network control solution assisted in the operation of the machines, as, via a single control interface, the entire safety system could be monitored, meaning that operators could quickly identify line errors and therefore reduce machine downtime.
José Cardenas, part of the management team at Heliene, explained that using automatic systems for both control and safety has improved both reliability and precision in the production process: "Compared with previous lines, we get more speed as well as improved quality, and relying on a single brand for the equipment makes maintenance and expansion much easier."
Oscar Chillón, process engineer, agreed with this: "Robotic manufacturing processes like this need production and safety systems that are reliable, versatile and flexible. We've achieved that with this line, and we've made productivity improvements as a result."
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