Which is the Best Solution for Work-in-Progress (WIP) tracking? One of the questions that I am frequently asked is, “Barcodes vs. RFID: Should I use Barcodes or RFID to track my work in process?”
The Merits of Manual (barcode) and Automatic (RFID) Tracking
In this white paper we explore the relative merits of bar code and RFID scanning for tracking work-in-process in manufacturing organizations, with a special emphasis on the needs of organizations that make custom and semi-custom products. Here’s what Dr. Peter Green from Bell Hawk has to say about:
How RFID Works
An RFID Tag reader periodically sends out an interrogating radio beam through an antenna. This antenna may be embedded into a portal or may be mounted in the ceiling to illuminate an area of about 6′ in diameter in an aisle or some other area through which the tags may pass. An antenna is then used to receive the response from each RFID tag in the area illuminated by the beam. If the RFID tag reader, which may control multiple sets of antennas, detects a response from any RFID tags it then relays their tracking numbers to an RFID control system over the plant local area network. This system detects whenever tags move from location to location and relays this information to a system like BellHawk, which translates the movement of the RFID tags into the movement of work-in-process parts.
Read Accuracy Issues
When deciding between Barcodes vs. RFID, know that RFID is good for detecting a small number of RFID tags passing through an area illuminated by an RF (Radio Frequency) portal or beam. The read accuracy in detecting a single RFID tag, attached to the outside of a pallet, when it is being loaded or offloaded from a truck/trailer is very close to 100%. The read accuracy of someone carrying a tray of 100 vials, each with their own RFID tags, walking through an RFID portal at the entrance to a laboratory drops to under 90%, which is unacceptable for a WIP tracking system. Barcode scanning accuracy is always 100% if validated immediately by a system such as BellHawk, and the user is immediately warned if they make a mistake. That is, provided, that the user remembers to scan the barcode.
Where Does RFID Works Well?
- Tracking the movement of custom assemblies from station to station. Whether on an assembly line or for assemblies that are moved from work-center to work-center, an RFID tag can be placed on each assembly at the first operation and then an RFID beam or portal used at the entrance to each work-center to record when the assembly arrives or leaves each work-center.
- Recording the movement of totes, carts, and trolleys containing WIP parts from location to location. In busy shops, these are often moved to random locations, just to get them out of the way, and are easily misplaced, resulting in lost time locating the missing, totes, carts, and trolleys. In this instance, the RFID tag only contains tracking number, making it easy to link to inventory tracking systems in place.
Barcodes vs. RFID: When to Use RFID and When to Use Barcode Scanning
RFID is good for recording the movement of big things, such as totes and large assemblies, each with their own RFID tag, where a high read accuracy can be achieved. It is not good for recording the movement of many small parts with their own RFID tags due to low read accuracies.
- The reason that barcode scanning is used for this application is to enable the person doing the assembly or mixing to be immediately warned if they are about to use the wrong part of ingredient or that these parts have not passed quality inspection.
- RFID is much more reliable than using barcode scanning to read barcodes on the totes. This is a case where the precision of barcode scanning works against it.
- At the end of the process control line, any subsequent manual operations on the contents of the carrier can be recorded using barcode scanning or the movement of the carrier recorded using RFID.
Minimizing Cost and Complexity
Using the simple tracking methods we described do not require the purchase of barcode label printers or special equipment to write information into the RFID tags. For use on assemblies, products, boxes, and cartons, rolls of combination barcode labels with embedded RFID tags, each with their own license-plate tracking number can be purchased from a number of sources including the economic MicRo Edge offered by PaladinID.
Dip your toes in the water…try an
RFID Starter Kit
ABOUT THE BELLHAWK SYSTEMS CORP
Dr. Peter Green is the Chief Technology Officer for BellHawk Systems Corporation. He led the development of the BellHawk software and is a recognized expert in the use of license-plate materials and work-in-process tracking methods as well as in the application of technologies such as barcode and RFID scanning as well as Artificial Intelligence to improve the performance of manufacturing and other industrial organizations.
About PaladinID, LLC
PaladinID develops and supports high-performance bar code labeling applications. We work with our clients to “Make Your Mark” by providing the expertise and tools necessary to create an entire product label printing solution. Located in central New Hampshire, PaladinID has been serving Massachusetts, Vermont, Maine, Connecticut, Rhode Island, New England, and beyond for over 30 years, and in 2017, became an RFID-certified company.