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November 16, 2007

Warehouse RF Network

It is becoming more and more common for warehouses to have an RF or wireless picking system. The advantages of the system outweigh the initial costs. Increases in productivity, inventory accuracy and order visibility reduce overall costs every single year as the warehouse becomes more adept at using the system. However the installation of the system has become a point of question to many looking at RF. Who should design the system? How do I know what I need? What am I missing?

Having built and fit-out several warehouses with this technology it is not going to be as bad as you think from a design and installation point of view. The key to a successful system install is to team with a quality and knowledgeable IT and Data Wiring vendor. Whichever vendor you ultimately select should have the ability to layout and procure the IDF cabinets, Access Points, wire pathways and all other equipment. They should know the proper specs and ranges for all of the equipment they recommend and should give you an electronic drawing of everything in your warehouse.

There are several aspects to an RF system that you will need to decide. The first is what kind of bar code technology will be used on products and locations. Wikipedia has a page describing the many types of bar codes that exist and their many uses. Most handheld scanners have the ability to read multiple bar code types, but it is still important to coordinate and make sure that everything is compatible from the bar codes to the printers to the scanners to the WMS. If you receive product from other vendors they may already have their own standard that you can use. Check with them if you are thinking of matching their technology.

In the typical warehouse there are many ways that bar codes will be scanned and many obstructions that could interfere with the wireless signal. Rack in particular is the biggest issue with warehouse RF. It is important to take into account several rack related RF issues during your strategy:

1) Lift Equipment Scanners - Vehicle mounted RF or Handheld units. Forklifts present several issues of their own. Vehicle mounted RF is typically more robust, more difficult to steal and more difficult to drop and break. However there is the additional cost to mount it to the forklift and you don't have the flexibility to use the scanner for floor picks.

2) Lift Equipment - Man-up forklifts or Man-down forklifts. The type of forklifts used in the warehouse come into play with where location tags can be placed on the rack. For man-up forklifts the tags will go directly underneath the product on the beams. In man-down environments the tags will have to all be placed on the first or second level to allow scanning. If there is a mixed environment there could be room for quite a bit of confusion.

3) Rack Density - The more packed together the rack in your warehouse is the harder it will be to get a clear signal to every point a scanner could be used. For a density of one pallet every 4 square feet you will need to have the wireless access points much closer together than for a density of one pallet every 7 square feet.

4) Rack Flexibility - If there is the ability to add and remove pick levels or locations there will be a need for a more flexible labeling scheme throughout the warehouse. The most flexible scheme I've come across follows the AA-12-34-56-78 format. AA stands for the rack type or forklift used to pick and putaway in the area. 12 is the aisle, 34 is the bay number in that aisle (odds and evens should be on opposite sides), 56 is the beam level within the bay and then 78 is the location on the beam. (ex. SS-23-34-02-02 would mean the location is in the Single Selective rack on aisle 23 in bay 34 (with evens being on the left) 2nd level up and in the right hand position.)

Once all of these issues are decided it is time to work with the IT vendor to actually develop the design. Don't stretch any of the equipment you get to its maximum range. Your IDF cabinets will likely be about 250 ft apart. Your access points will be staggered throughout the building on about 100 ft to 150 ft centers depending on rack density. With a 500,000 sf building your probably looking at a 400 ft depth which gives you two rows of IDF cabinets running along your building and 3 rows of access points. There are a lot of items that need to be coordinated so much sure you develop a robust plan for what you want and need this system to handle.

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There has been a lot of interest in this post. If you have any additional questions feel free to email me at dmusic [at] integratedstrategiesinc [dot] com .

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