Color sensors help with transmission manufacture

Birgit Gottsauner -- Control Engineering, 4/1/2006

A German transmission manufacturer is using new color area sensors in a pilot application for inspecting colored sealing plugs. Dustproof and splashproof devices can learn and save as many as 16 color samples without programming and complete up to 30 inspections per second.

The Saarbrücken plant of ZF Getriebe GmbH is headquarters of the car driveline technology division of ZF Friedrichshafen AG, where 4-, 5-, and 6-speed automatic transmissions for passenger cars are developed and manufactured.

Daily output of approximately 4,000 transmissions in 14 types and 120 models requires strictly organized, highly automated production processes, and quality management at every step. This includes inspection of sealing plugs before and after transmission washing. Plugs cover connections for the cooling system and prevent wash water from entering the transmission interior.

Proper fit of the yellow, white, or orange colored plugs is automatically checked with intelligent cameras. Before washing, where other characteristics are inspected as well, the intelligent camera, Siemens Simatic VS 710, acquires complex grayscale images to compare with nominal samples.

'After the washing, only the presence of the plugs needs to be checked,' says Klaus Kimmling, who is responsible for factory automation IT tasks at ZF. 'Even simpler industrial camera systems on the market are actually too oversized for this, which is why we have been searching for a long time for an equally rugged, but cost-optimized solution.'

Kimmling looked beyond conventional binary sensors to color-area-sensor technology, Simatic MV220 from Siemens Automation and Drives (A&D), for durability, reliability, and availability. The Saarbrücken plant, often among initial users of new Siemens automation technology, tested the new color area sensor in a pilot project.

'One of our core requirements was to be able to adjust the sensor quickly and easily to different inspection tasks without complex programming or profound image processing knowledge,' says Kimmling, since different transmissions use sealing plugs of different colors in varied locations.

IP65 sensor enclosure protection, dustproof and splashproof, meets application requirements. The package includes a color area sensor, an I/O interface for digital data exchange with the controller, a laser-based alignment aid, and lighting. Dimensions of 113 x 35 x 90 mm minimize space taken at the production line.

A control panel is located atop the device. In a few steps, up to 16 OK-images can be taught and stored in the sensor. Images are then analyzed and compared to photos taken of the test items. The device automatically adjusts exposure time, white balance, and brightness correction. To focus the unit, the operator or setup technician uses an adjusting screw to change the detection window from 40 x 30 to 200 x 150 mm.

Sealing plug inspection runs automatically after washing. The controller activates the corresponding OK-image via the digital inputs of the color area sensor, briefly stopping the assembly line and triggering the image at the right moment.

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Touch Panel Simatic TP 170B is used for operation and monitoring at the assembly line.

Since start of production in 1973, the ZF plant (which employs more than a fifth of all people working in Germany’s Saarland area automotive industry), has produced more than 10 million transmissions. Clients include leading carmakers worldwide.

To check the correct functioning of the inspection system, ZF runs a “reference master” (a transmission without plugs) through the inspection stand three times a day. An offline table in the controller locally stores the last 10 transmission-type checks, to move past possible downtimes of the overriding control system, perhaps for quick maintenance.

Touch Via the mobile data storage unit of the RFID system Moby I, transmission type is identified and sent by the control system to the PLC, which activates the corresponding test image in the sensor and triggers the image.

Klaus Kimmling, responsible for factory automation IT tasks at ZF, configured the new color area sensor for the pilot application. He praises the intuitive teach-in procedure and variable adjustment of the image window and object distance, which “shortens our changeover times without having to forego powerful image-processing features.” The inspection system has been running stably and reliably for about a year and is said to fulfill assigned tasks economically.

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