In the German Conergy factory four robots assemble solar cells to matrices. Smart cameras, integrated on the soldering heads of the robots, manage the precise position detection of the cells. Displacement sensors take care of the high quality in final assembly through the exact determination of the protective film‘s edge position.

In its German solar power systems factory Conergy produces photovoltaic modules capable of generating an annual output of 250 MW. For this, five fully automated assembly lines run with more than 40 industrial robots from ABB on a total production space of 35,000 m². The solar cells are transported from the cell production to the module manufacturing area. Next, the individual solar cells are fed to the five autonomously operating production lines. There, the solar cells are connected automatically into a chain of cells (string) by the so-called stringers. The task of connectivity of individual strings into a matrix - the actual photovoltaic module - is carried out by four robots per line, each of the IRB 1600 series. In this step precision is essential.

Smart Camera Controls Soldering Head
Two of the four robots are equipped with a special suction gripper, and they handle the soldering blocks, insulation foils, and soldering ribbons. The two other IRB robots operate one soldering head with integrated IVC-2D Smart Cameras. The cameras help to determine the orientation and position of the cells and of the small soldering ribbons on the top and bottom of the module. The industrial vision camera detecting in 2D offers resolutions of 640x480 up to 1,024x 768pixels, combining the latest image processing technology with a highly efficient program library for image evaluation. Thus, over 100 software tools are available. They can be used for the detection of characters, figures, and logos. Shapes, geometries, sizes, or designs - the user can adjust the camera via the graphic programming interface to the respective task and environmental conditions in object detection. The robust and compact housing is constructed for industrial operating conditions. Apart from three freely programmable inputs plus one trigger input as well as three freely programmable switching outputs, the IVC-2D features an Ethernet connection for fast and easy creation of a communication network. It can be used to transmit data and parameters to the machine controller easily. Apart from precision ABB Automation praised the simple programming, high immunity to ambient light and that the IVC-2D does not require any additional processor or computer support for operation.

High Precision Edge ­Location
Every 100 seconds, one interconnected module leaves the robot work cell via a conveying system. In the next step of the process, a protective film made of EVA (ethylene vinyl acetate) as well as a weatherproof composite plastic foil are placed on the module. Afterwards, four modules per line pass through two laminators, where the solar glass, the cells, and the films are "baked" for approximately 17 minutes at 150 °C into a solid, weatherproof unit. Once these laminates have cooled to room temperature, a robot carries out the so-called edge trimming - the cutting of foil remnants projecting beyond the edge of the module. For this purpose, the robot takes the encapsulated solar module, puts it down, and mea­sures, accurately to a few µm the edge positions using an OD MAX displacement sensor.
The OD MAX series includes high-­precision distance sensors in four variants for operating distances from 24 to 26 mm, 25 to 35 mm, 65 to 105 mm and 250 to 450 mm. The CMOS sensors fit for quality control and precise position tasks due to the measuring accuracy of 0.1 % of the measuring range. The slightest changes in distance or height fluctuations are detected by the sensor reliably and accurately to the µm like the edges of the solar modules before removing the protruding remnants of foil.
The position data resulting from the precise measurement of the module's edge position by the OD MAX are used by the robot controller for guiding the cutting implements, ensuring exact trimming of the projecting foil remnants directly on the glass edge of the module. Accurate cutting is crucial for the quality of the solar module, since any damage of the foil would foster the penetration of moisture. In the penultimate pro­cess step, the solar modules are inserted into torsionally stiff and extremely weatherproof modular frames. In the last step, the module, almost ready for shipment, is fitted with a connecting box and undergoes testing for its performance data.

Sensor Solutions from One Source
In order that automated manu­facturing processes for solar cells, such as the ones at Conergy, reach a maximum amount of reliability and availability, the portfolio from Sick offers - apart from IVC-2D and OD MAX - additional sensor solutions. Examples therefore are optoelectronic, electromagnetic, as well as ultrasonic sensors in handling systems and solutions for identification of solar cell boxes, solar modules, or individual solar cells. Added to this are camera sensors such as Inspector, e. g. for inspecting edge fractures on solar cells, as well as solutions in machine vision for additional, diverse inspection tasks associated with solar cells. On top of that, electromechanical or optoelectronic safety systems - primarily the V300 WS camera sensor and a compact generation of light grids - provide for an optimum combination of safety, availability, and ergonomics, e. g. on partially automated work stations as well as on fully automated robot work cells.