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SUPPLEMENT FEATURE MACHINE VISION SYSTEMS AUTO IDENT – NO SILVER BUL


Tim Stokes, SICK (UK) Auto Ident specialist looks at the differences between code reading options


on investment) can be significant. RFID systems also need careful set up in areas where radio signals could be masked or reflected, for example, where multiple metal surfaces are present.


SICK bar code scanners can accelerate logistics and automation processes. Their high scanning frequency permits high process speeds, and simple networking improves operational efficiency


“ I


suppose it is tempting, if the only tool you have is a hammer, to treat everything as if it were a nail.” These words by psychologist Abraham Maslow in 1966 have been adopted by industry as a warning against over-reliance on a familiar tool or technology. Maslow’s fascinating observation of


human behaviour is particularly apt in the field of auto-identification technologies. For more than 15 years, users in factory and warehouse automation have been confused by some claims that one auto-ident solution fits all: RFID, camera or laser. Clearly, Maslow’s observation,


sometimes called the ‘golden hammer’ underlines the fact that there is no ‘silver bullet’. Put another way, a single solution is not necessarily the answer. An intelligent choice of technologies is what truly makes the difference. It’s natural to stick with a technology that is familiar and comfortable, not least because it eliminates the risk that data communications between devices will be disrupted. This can be a false security. Achieving effective and consistent auto-ident results is about using the best technology for the task at hand; the optimum solution will not be the same each time. Aside from the auto-ident device chosen, it’s equally important to consider how the device will perform on many platforms and interface to multiple devices, such as PLCs and BUS systems.


WEIGHING UP THE BENEFITS Given that there are a range of auto- ident technologies for different tasks,


S18 OCTOBER 2015 | MACHINE VISION SYSTEMS


let’s examine the pros and cons. The three major auto-ident technologies are Radio Frequency Identification (RFID); vision cameras covering matrix and line scan technologies; and laser readers. Cameras and laser readers, which encompass 1D and 2D code scanning, are the basis for a large proportion of auto- ident operations.


CENTRALISED OR DECENTRALISED Is a centralised solution needed with all data and production history held on central PCs and servers? Or is the production history held on the label of each product as it progresses through the process? If a decentralised system is in operation, then RFID could be the only real choice. RFID offers unique benefits: • Tags can be read from any direction, so locating the reader is not as critical as optical systems and line-of sight is unnecessary. The tag to reader range can be very large compared to the other technologies. • For high speed throughput, reading is


very rapid and many tags can be read at once.


• Tags can carry large volumes of


complex data, which can be rewritten, amended or updated easily. • RFID performs well in harsh factory


environments where there is dirt, dust or high moisture levels, for example. But RFID can be expensive. Reliable transponder tags are about ten times the cost of a printed label and many tags may be needed in the supply chain as well as in the factory; the effect on ROI (return


/AUTOMATION


READING CODES - CHOICES AND OPTIONS If a centralised system is acceptable, then either a barcode or 2D code is likely to be the answer. Generally the 2D code is becoming widely used because it can be read in any direction and stores a larger amount of data in a smaller space than a 1D code. However, 2D codes need a camera to read them, which is more expensive but worthwhile if large amounts of on-pack data are necessary. A camera is also better at reading low contrast coding in 1D and 2D. A simple laser reader will be the answer


if all that is needed is to read simple SSCC (standard industry) or in-house barcodes on the side of a pallet, say, to check goods in or out. With wide scanning height and width, it can sweep the entire side of a pallet, with cell sizes down to 3mm.


CANDID CAMERAS Cameras can read 1D, 2D and plain text coding. They can provide live and stored images for analysis and storage. Reading is omnidirectional with just one device and poor code qualities can be read consistently.


The SICK CLV62x series of bar code scanners are compact, powerful tools for a wide range of logistics applications


MATRIX CAMERAS Matrix scanner cameras offer the benefit of reading in any direction or orientation. They can cope with low contrast and


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