For inspection applications where photoelectric sensors can’t get it done and vision systems are overkill, Cognex Corp. (www.cognex.com; Natick, MA) has developed the Checker 200 series. Or, as Gregory S. Wiese, the company’s senior manager of Sensor Products marketing puts it, “When you don’t need full vision but other sensors aren’t ideal.” He describes the Checker 200, which is predicated on the company’s Checker 101, which was introduced in 2004, as providing “photoelectric sensor simplicity, but for more challenging applications.” The 200 is a 2D CMOS sensor device that measures a compact 67 x 36 x 70 mm. It offers variable working distance capability, so given its size and that capability, it can be easily integrated into production operations. It has built-in lighting, which also helps in setup. On the back of the IP67 housing there are quick-disconnect cables and USB 2.0 connectivity (which facilitates runtime imaging).
Unlike a photoelectric sensor which essentially indicates whether there is something detected or not, the Checker has a few advantages, such as being able to detect features (e.g., graphics) and operating without precise part handling or fixturing. It can also be programmed so that it can deal with several different parts. There are actually three different types of sensors integrated into the device: brightness, to find dark and light areas; contrast, which facilitates finding features like threads or codes; and pattern, to find features that it has been “taught” to find. It has the ability to inspect some 6,000 parts per minute. Setup is simply performed via a PC-interface. The PC also allows users to actually see what the camera is looking at, either for purposes of setup or should the user want to get a look at what the camera is seeing in real time (perhaps to determine what is the cause if there are part failures).
Among the automotive applications that Wiese notes are verifying the presence of threads in a bore, detecting double bearings, and verifying whether a clip is in place. He suggests that because it doesn’t depend on precise location of the part, it is applicable in operations such as powertrain, body and chassis.—GSV