Color sensor checks auto plugs

At its Saarbrücken, Germany plant, automotive-parts manufacturer ZF Getriebe must inspect colored plugs used in transmissions to seal out water during a washing process. The plant produces approximately 4000 four-, five-, and six-speed transmissions a day, comprising 14 basic types with 120 variants. Production must be tightly organized, and every step in the workflow must be integrated.

To inspect these plugs at speeds up to 30/s, the company installed Simatic MV220 sensors from Siemens (Munich, Germany; www.automation.siemens.com). The sensors collect information solely from the colors of the plugs, which means the volume of data to be processed is very small--about 4 kbytes--and complex images can be read quickly. The 640 × 480-pixel sensor creates a data list after an image has been recorded. The list gives only the color spectrum and the brightness levels of the image. Each image is represented by its own unique cloud of dots, which the system compares to a reference image. The inspection results are processed at a central location and sent to an RFID data-storage device, which accompanies the transmission through final assembly.