Opel’s factory in Rüsselsheim relies on innovative technology in production. At a welding robot, various stamped and deep-drawn metal sheets are welded to form a supporting element of the bodywork. A 3D camera from ifm electronic monitors the position and the fixing of the sheet metal parts.
The O3D sensor
ifm’s O3D302 vision sensor is a 3D camera with integrated image evaluation. The resolution of the PMD image sensor is 176 by 132 pixels. For each of the 23 232 pixels the sensor supplies a precise distance value – up to 25 times per second. In contrast to laser scanners, this sensor has no moving parts, making it especially robust, small and cost-effective.
Since the 3D image is evaluated in the sensor, external image evaluation is not needed. The distance between the clamp and the sensor is evaluated via definable positions in the camera image (regions of interest). The integrated evaluation detects if the tension lever is open or closed. The events are transferred to the controller using the Ethernet interface via TCP/IP, Profinet IO or EtherNet/IP. Using the Vision Assistant software, the user can easily set the sensor parameters, define regions of interest, or configure the output function, for example.
Looking down from the top
Two of these sensors are installed above the welding system, both looking down to the sheet metal to be welded. Fabian Gulla, application engineer for image processing and robotics in plant construction at Opel, explains: “We use the sensor for distance measurement and have defined several regions of interest, which we detect. The advantage of the O3D is that you only need one sensor and can then redefine the regions of interest in the software. Then we simply use the distance measurement for detection.”
Visualisation and space saving
For transparency in the process, Opel has installed a monitor for visualisation in the plant. Besides graphic process visualisation, the O3D can also provide a live image. The advantage of the ifm sensor is that positions can be assigned to the clamps and components visualised in the image. A red-green colour change symbolises to the operator if a workpiece has been placed and if the clamp is open or closed.
Since now only one sensor is needed for the detection of several positions and this sensor is installed high above the plant, there are special advantages for the construction of the plant.
Prospects
The experience at the Opel plant will have a positive influence on future plant construction. “The cooperation with ifm has been excellent,” concludes Gulla. “We had several meetings directly with the developers, so we could gain insight into how the sensor works, what we needed to note and what size objects could be reliably detected. The use of the O3D sensor provides us with completely new possibilities.
“Fewer sensors, simpler plant construction, no interference due to weld spatter – the vision sensor as a monitoring system provides numerous advantages and considerably reduces the plant cost by reducing cabling, installation requirements and I/O points at the controller. Our other production plants can also be equipped with this vision sensor and thus optimised.”
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