Faraday Cage vanquished

Using RFID in warehouses with a lot of steel in racks and walls, leads to reading problems because of the Faraday Cage effect. However Dutch/Belgium company DL Tech succeeded in using RFID in the cold stores of food manufacturer Ter Beke in the Belgian city of Wanze.

Lasagnes need cold storing

In Wanze (near Liège) Ter Beke produces lasagnes. For optimum taste and tenability cold storing and cold transportation is needed. This used to be handled by a specialised logistics service company but a few years ago the Ter Beke management decided to keep it in house.
To realise this, a new cold store was build and from this location Ter Beke ships its lasagnes and other cold kept foods to main supermarket organisations in all European countries.

High turn around movements

The new warehouse is opened at the end of 2004 having about 1,500 pallet storing locations. Daily in and outputs are about 1,000 to 1,200 pallet movements. To realise these high turn around movements Ter Beke relies on a new WMS, which was developed by Belgian software supplier Data-M in co-operation with consultant Jan Colders of Belgian logistics consultancy company Execon.log.
The WMS uses pallet storing location identification either by bar code as by a H.F. RFID system, installed by DL Tech.

Efficient and faultless working

The decision to use both the identification techniques has been made because of the high speed throughput of delivery orders and the wish to have the reach truck drivers working efficiently and faultless.
It was also made because of the relatively small floor capacity. This leads to build high racks and therefore the warehouse has roll through racks on four levels upto a height of six meters. They are filled and emptied by three reach trucks.

Why the combination

Ter Beke’s ICT-manager Koen Vandenabeele explains how this combination of bar codes and RFID tags supports the more efficient and faultless working by the reach truck drivers: “On the lower storing locations we use bar codes. They are read by a conventional scanner, because their good visibility for both driver and scanner. However scanning of the higher locations nearly is impossible and that is why we use RFID at these racks”.

The Faraday Cage

But as we know, RFID in metal-filled environments comes to reading problems. Research by the Dortmund University (Germany) learns however that RFID tags of the H.F. type using a frequency of 13.56 MHz (according to ISO standard 15693) is possible in an environment full of metal racks.
Thus when de RFID supplier knows what to do by knowledge and by own experiences. DL Tech’s Marketing and Sales Manager Rudolf Renfurm, who is also leading RFID spokesman for AIM Nederland, says that the problem of the Faraday Cage occurs because of the minimum transmission power in so called passive tags (tags without a battery). “Their transmission possibilities are very low which leads to high circulation of the radio signals through the warehouse without reaching reader nor tag”. Even when only a distance of a few inches have to be bridged, which phenomenum is known as the Faraday Cage effect.

Solution

DL Tech found the solution via a special housing for the tags and a special way of mounting them by using a fitting piece between tag housing and rack.
The solution appears to be very effective.

Photo: Rudolf Renfurm has solutions against the Faraday Cage effect

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