Delft University of Technology
Faculty Mechanical, Maritime and Materials Engineering Transport Technology
J. Rijswijk Feasibility study on item level tagging with EPC Gen2 UHF RFID technology for a zone pick process in a distribution centre Masters thesis, Report 2006.PEL.7107, Production Engineering and Logistics.
UHF RFID is a fast developing automatic identification technology which makes use of Ultra High Frequency radio waves to identify individual items. An item is tagged with a RFID tag (consists of chip and antenna) and the chip is programmed with a unique number which identifies the item. By radio wave communication this data can be captured by a reader device of the RFID system.
Vanderlande Industries is convinced that in the near future every product will be carrying an RFID tag instead of a barcode. They are interested in the added value of RFID for the automation of their material handling systems and especially for a zone pick process. They are also interested in the status of UHF RFID technology to keep up with its development. Benefits for Vanderlande Industries for a zone pick process:
Real time information on stock levels Automated order control
Improved handling efficiency Higher productivity
A zone pick system is a logistic process of picking orders with automated conveyor transport of containers from zone to zone through a distribution centre. The system consists of one main conveyor loop which connects all workstations. When an order is made by a client an empty container is assigned to the order and sent into the main conveyor loop. In the picking zones the container transfers from the main conveyor loop to a workstation. In this workstation bulk products are stored in shelf containers and are picked by hand into the container. When every product of the order is picked, the container leaves the loop and is sent to the dispatch area. At this end-station, the picked products are repacked into cartons and the order is checked for correctness. The process has a high reliability of 99.5% and the 0.05% errors are caused by human actions.
Articles are picked from the wrong location Number of articles picked is not correct.
Bulk articles are stored on the wrong location in the shelves. RFID could solve these problems in theory by:
Placing RFID antennas at every container on the shelves for content control and employees on their actions.
Automatic order control of a picked container in a workstation with a RFID scanning portal, so errors made will be noticed. Automatic order control of a picked container before the dispatch area with a RFID scanning portal, so errors made will be noticed.
These points are the most important innovation objectives for this research regarding reliability. Other objectives regarding handling efficiency are only important when reliability can be guaranteed. A technical feasibility study enables the possibilities for innovation with UHF RFID. The study is build up in three stages from laboratory environment to process environment. Every influencing factor is taken into account: negative influencing factors are tried to exclude and positive factors are used to increase readability performance.
Test results show that UHF RFID technology is not feasible for item level identification in a zone pick process. Technical shortcomings which decrease the reliability are:
Tags stop functioning when placed against each other.
Tags can stop functioning when positioned too close to each other.
Tags can stop functioning when placed against material with a transmission coefficient smaller than 0.79.
Only for a small group of products it has potential (T>0.79), but only when packing conditions of a container are taken into account to avoid tags being too close to each other. Packing conditions for an employee are not an option for Vanderlande Industries, because they will lead to more human errors and decreasing handling efficiency.
UHF RFID has the potential to be a mature automatic identification tool. If further development of technology could lower the tags' sensitivity to item material, the key problems to success can be avoided. Therefore the conclusion is that UHF RFID is not feasible yet for item level identification in a zone pick process.
Reports on Production Engineering and Logistics (in Dutch)
