RFID tag placement: unit-load tagging, on a pallet or otherwise, is not so simple as it looks. After all, someone has to be able to read it once the shipment is delivered

Frontline Solutions, June, 2004 by Brian Albright

Right now everyone--including solution providers--is on a steep learning curve when it comes to radio frequency identification (RFID) technology. Initial tests of RFID in the supply chain between large retailers and their suppliers have been promising. Those just starting down the RFID path, however, face significant engineering challenges as they begin tagging cases and pallets.

Each supplier and retailer must thoroughly test RFID in its own operations and do as much research as possible on other pilots to avoid re-inventing the wheel. Each should also take vendor claims with a grain of salt. "We had to forget a lot of the things the sales rep told us, get beyond the RFID hype to make this work, and we did a lot of engineering," says Mike Nolan, owner and founder of systems integrator Automatic Identification Systems (AIS). "It scares me a little that so many people are listening to the hype."

It can work, says Ralph Rupert of the Center for Unit Load Design at Virginia Polytechnic Institute and State University. Rupert's team has tested RFID tags on pallets and found that the technology can fail in a typical warehouse environment if not applied properly. He emphasizes, though, that the goal of the Virginia Tech study was to alert companies to these issues before they even begin their pilot programs. "We want to make sure we're raising the flag on these concerns," says Rupert. "If these problems aren't addressed early on, customers will set themselves up for failures downstream that will give a black eye to the technology."

The Demolition Derby

Most of the work right now is at the case level, where the RFID tags are closer to potential sources of interference (metals that reflect the radio signal, liquids that absorb it). If you've cracked case tagging, the logic goes, tagging the pallet should be comparatively simple.

Maybe not. Some pilots have shown that not only are pallet tags as susceptible to interference as case tags, but they're also vulnerable to wear and tear in the warehouse that could render them unreadable once they reach their destination.

"Impact hazards on pallets are extreme," says Rupert. His team tested pallet tags for one manufacturer in a simulated warehouse environment. "The tags were severely damaged with only a few impacts," he says.

In the Virginia Tech tests, tags were subject to forklift and pallet jack impacts that reached 5,000 to 7,000 pounds per square inch--quickly demolishing the antenna, which was encased in a 4-by-4-inch molded polypropylene casing. (The tags were prototypes provided by Finnish RFID manufacturer Rafsec.)

Tag placement is fundamental, according to Rupert. The metal mass of the forks can cut off the signal to the tag or reduce the read distance. Moisture in a wood pallet can also reduce read distance. Rupert says the tag has to be offset from the wood structure to increase performance, although this can increase impact potential. He adds that two tags could be needed to ensure a drive-through read at a dock door.

Several companies (systems integrators, pallet manufacturers, and end users alike) have developed ways to mitigate the interference and environmental hazards. Users also have more flexibility in tag placement than they might think.

Although everyone involved in the push for adoption of the RFID-based Electronic Product Code (EPC) protocol has consistently referred to "pallet tagging"--from Wal-Mart to the Department of Defense to most technology vendors--what they're really talking about is tagging the unit load. That means the tag can go anywhere on the load as long as it's readable--on the pallet itself, on the last carton on the pallet, or even on the stretch wrap.

"We see little value in applying the tag on the wood," says Chris White, IT supply chain leader at The Stanley Works, New Britain, Conn., which has been piloting the technology. "We intend to put the tag on the outside of the stretch wrap."

But there is no simple answer. The best placement for the tag will depend on the material being shipped, and right now figuring that out requires a lot of testing.

"Determining placement is very time consuming," says George Reynolds, vice president of RFID at Tyco Fire & Security. "You have to go through each possible scenario to know if you passed the readability requirements."

Location, Location, Location

Tag placement has emerged as an important factor for both case and pallet tagging in every pilot conducted so far. "Placement is going to be critical," says Joe Jiner, logistics and RFID development director at The Kennedy Group, a consultancy that operates an RFID testing lab. "On a case of liquid product, we'll test six areas where we can place a tag, and only one or two of those might give a best read."

Jiner recommends automatic application of smart tags to ensure uniform placement--hand application is just too inaccurate and time consuming.

In its own pilot tests, Tyco Fire and Security determined that a one-way pallet (where the forks can enter the pallet from only one direction) could be tagged with one RFID device. With four-way pallets, the pallet had to be tagged on each side to ensure readability.