“Achieving Effective Inventory Management, 5th ed.” is written by Jon Schreibfeder, president of Effective Inventory Management. The book is designed to help distributors meet or exceed customers’ expectations of product availability and to minimize total inventory investment. The following is excerpted from chapter two, Get Your (Ware) House in Order, and outlines some warehouse inventory management tools to use with a bar coding system.
Voice Picking SystemsOne of the biggest complaints about bar code systems is that most bar code readers or RF guns must be held by the user. This leaves only one hand available for handling material. Voice picking systems solve this problem. Each picker wears wireless headsets with a microphone. The WMS broadcasts the next bin location whose product needs to be picked. When the picker arrives at the bin he reads the last two or three digits of the bin location, or bar code number of the item, to verify that he is at the correct bin. The system then informs him how many pieces need to be picked.
Voice picking has proven to be very accurate. Many of these systems average less than one picking error for every 1,000 lines picked.
Pick to Light SystemsPick to light systems are another alternative to bar code readers that work very well in high volume pick faces with relatively few inventory items. In many cases a tote that will hold the pieces to be picked to complete an order arrives by conveyor in front of the pick face. A two dimensional bar code is affixed to the tote. This bar code contains a pick list with all of the items and quantities of those items to be picked. As the system reads and processes the pick ticket bar code, the picker is guided to the next item to be picked by an illuminated light in front of the bin. A digital display on the bin informs the picker of the quantity to be picked. The picker confirms that the item has been picked by pushing a button next to the bin’s digital display. This action also prompts the system to illuminate the light containing the next product to be picked. When all of the line items for products stored in one section of the pick face have been filled, the conveyor moves the tote to the next section of the pick face and eventually to the staging area for packaging.
RFID Bar CodesA common problem with one and two dimensional bar codes is that they require a direct line of sight. That is, a bar code must be “seen” by the bar code reader. Radio frequency identification (RFID) bar codes are designed to overcome this problem.
Each RFID bar code label contains an integrated circuit meant to communicate with the RFID bar code reader (commonly known as a “portal”). When the package containing a passive RFID bar code passes by or through the portal it receives a signal from the reader and sends a confirmation that its information has been read.
Some RFID labels are passive. These labels do not have any internal power and must use power received from the portal in order to respond. Semi-Passive and Active RFID labels contain some battery power and generally have a greater range and more tolerance to interference than passive labels. Active RFID labels are similar to GPS units and can be used to identify the location of an item in a warehouse.
Theoretically you could push a pallet loaded with 45 boxes with RFID labels through a portal and the reader would receive data from all 45 boxes. But there have been some problems with consistently reliable label reads particularly with items made of certain materials. As this technology continues to evolve, the reliability of RFID label reads continues to improve. Just as important, the cost of labels and all of the equipment necessary to implement an effective RFID system continues to decrease.
It is not easy to get control of your inventory. Most companies have thousands of pieces of various products moving through their warehouses at any one time. But if your warehouse is not in order, and you do not follow established “best in class” procedures, you will have to stock extra material to compensate for your sloppy ways. And your cost of filling orders will be prohibitively high. Effective inventory management will be impossible.
To order a copy of “Achieving Effective Inventory Management,” visit www.naw.org.