Getting parts from here to there is one thing, but knowing what happened to them along the way is quite another. As systems have gotten more sophisticated, users have been able to merge the two tasks of material handling and parts tracking. One of the more recent developments is radio frequency identification (RFID).
Basically, RFID is the next evolutionary step in the bar coding family. Instead of printed bar code labels, there are radio trans-ponder tags that can contain memory and processing power. How much memory a tag contains varies from only enough bytes to hold an ID number, to several kilobytes for holding, for example, all of the work-in-progress data of an assembly. Unlike bar code labels, information can be updated or changed, and they can be used again and again. In the case of Omron Electronics Inc.'s (Schaumburg, IL) V600-HA Intelligent Flag system, the tags can be reused at least 300,000 times.
Sure, if they last that long, right? Tag durability is an issue RFID system designers have been dealing with. Most tags are sealed, encapsulated, or otherwise engineered to withstand nearly anything the factory floor can dish out. For example, HotTrak RFID tags fromRockwell Automation (Milwaukee, WI) are designed to take the heat of things such as paint shop applications. The tags' plastic housing can withstand temperatures up to 200°C.
The other component to an RFID system is the reader, or antenna. These units send out a radio signal that activates the tags, which send information back to the reader. Most readers work within the low-frequency range of about 120 to 130 kHz. Systems with frequencies higher than this are more costly, but they give users greater read/write ranges between the antenna and the tags.
Since RFID systems are radio-based, they need regulatory approval, and must meet the standards of a couple of different organizations. Don't let this intimidate you. The hassle of making several government agencies happy is handled by the manufacturer.
IDing the ID system
Combined into a system, the reader/antenna and tags can be classified as either passive or active, and as either read-only or read-write. A passive RFID system has tags that do not contain their own power source. Instead, they rely on the reader for power (sort of like a magazine editor). Tags in an active system have their own power source, most likely a small, lithium battery. Passive tags are generally less expensive, and have a theoretically indefinite life, but active tags have a higher reading range.
The difference between read-only and read-write systems is also a matter of what the tags can do. With a read-only system, tags are preprogrammed with a unique identification code or other bits of information, and that can never be changed. Read-write tags can have their data updated, added to, or changed all together.
RFID systems offer several advantages over traditional tracking systems. One of which is that more information can be encoded into the tag than other systems, such as bar coding. And while many potential users balk at the initial investment (tags alone can cost anywhere from $10 to $50 apiece), those who are already using RFID systems point out that it is basically a one-time cost. Transponder tags can be used again and again, whereas bar code labels can only be used once, so you're constantly buying new ones.
RFID systems are also more dynamic than the average material/product tracking system. They change and grow as often as needed, and the information in each tag can be changed and updated as the part moves from process to process.
While all RFID systems have the same basic components and capabilities already mentioned, each system maker adds its own "zing" to its system. The Intelligent Flag system touched upon previously from Omron Electronics gets its "zing" not only from the longevity of its tags, but also from its ease of use. The system does not require any specialized programming at initial setup, and users don't have to spend hours checking for proper positioning and possible interference during installation. The system is not influenced by either factor.
The Intelligent Flag system can be used as a stand-alone system, or it can be connected to PLCs, sensor controllers, and other devices for more advanced data management. Users can choose between the V600-HAR91 read-only amplifier, or the HAM91, which reads, writes, and verifies tag data. Both of the models have the ability to run in auto mode or in an external-trigger synchronous mode.
Durability is key to the IntelliTrak RFID system from Rockwell Automation. Not only are the tags epoxy-encapsulated for harsh industrial environments, so are the antennas, which also don't contain any moving parts or mechanical switches. This cuts the possibility of future maintenance problems significantly.
But toughness doesn't mean you sacrifice functionality. The antennas are capable of converting digital signals from controllers and other data devices into radio frequency signals, and vice versa. Other features of the system include variable tag-to-antenna orientation, three variations of data tags, and up to 32Kb ram on the tags.
In more ways than one. Returnable packaging is nothing new, but some companies are, well, thinking out of the box, so to speak. Here are just a couple examples:
Here To There
Here's a quick look at a few systems designed to keep things moving:
The Intelligent Flag controller from Omron Electronics is surrounded by the eight photoelectric sensors it replaced at a Panosonic installation.
The Link-Belt bearings pictured here are a part of the conveyor system at the painting facility at Ford's Ontario Truck plant.
A lot of little parts go into putting "zing" into the Plymouth Prowler. Shipped in from suppliers, the parts (in their properly colored containers) are placed on flow racks along the assembly line. When empty, they simply go to the return flow lane where they are picked up and shipped back to the supplier where they are filled up and shipped back.
A robot in the Peak Industries' conveyor system designed for Ford places each windshield onto a storage rack as it comes out of the bending oven.