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Effective RFID Work in Process (WIP) Applications

In trying to improve business efficiencies related to time, materials, rework, defects, and other areas, questions regarding work-in-process (WIP) situations can be challenging to answer. This article will explain some ways in which RFID may be used in WIP applications to improve your business operations. It will address the “where, when, what and how many” questions that you may have about your WIP. With intelligent reporting, the “why” answer may also become evident.

The principles described here also apply to other in-process situations. These may include a product testing process, a time-out-of-environment (TOE) workflow in transportation or pharmaceuticals, or other situations.

What is a WIP application?

A work-in-process application is one that helps you keep track of information about work as it is being

accomplished, such as a product as it is being manufactured or assembled. With RFID, this involves setting up readers, antennas and tags through the workflow or process. For example, a tag can be embedded into the product that is being made, or a tag can travel along side the product or group of products. In the latter case, the tag may be attached to a job folder that moves from station to station.

A RFID WIP solution will typically divide up the work into zones. Each zone has an RFID reader(s). By dividing up the process into zones, the RFID solution can measure time, quantities and location, the “when,” “how many,” and “where” knowledge of the process. When different types of goods are created in the same process, we also gain “what” knowledge. For example, if you manufacture “good, better, and best” products, you can keep track of each type of product created in the manufacturing or assembly process.

Saving time through “where” knowledge

“Where is my product?” may be a question that is asked by a customer or supervisor. An RFID WIP application can help you know the location (the “where”) of a product or job in the manufacturing or assembly process. Having multiple RFID read zones can tell you where the product currently is. Previously, this information may have been obtained by walking through the assembly process to find a specific product or job folder, taking valuable time away from other operations. You can employ a barcode system, but that requires operators to stop the work in order to scan a barcode. RFID is fully automated. RFID can greatly reduce the time required to locate a particular item.

Measuring time with “when”

A well-designed RFID solution for WIP applications provides both time stamping of reads and time deltas between the different stages of the work. The timestamps tell you when events occur, such as a pallet moving from storage to the production line. Time deltas measure how long, such as the amount of time elapsed for the pallet move. The deltas help show where operational bottlenecks or inefficiencies, are located. “How long does it take to rework a product” may be answered with time deltas.

Measuring work rates, defects, and other KPIs

In addition to determining where and when, you can also keep track of what and how many. If an RFID tag is placed on each item being assembled, you will know how many items were created in a specific amount of time, and of what type. For a company that has a defect process, the WIP application can record the number of defects, time for defect correction or other relevant information.

Converting from raw materials to finished goods may generate yield loss. Having RFID tags on both raw materials and finished goods aids calculating both yields and loss. Lean processes benefit from this information in improving the process (build-measure-learn feedback loop).

Counting in zones and between zones can help you learn information that is useful to operations. For example, how many widgets does line 1 produce compared to line 2? Is there a difference? If so, look at time data to understand why. At what point is your product most frequently sent to rework? A high transition from station A to rework can point to some problems with the current process. Counting can also provide insights into inventory levels, inventory value, and more.

Deciding on RFID use

At this point, you may be wondering, “is RFID worth it?” If the points mentioned above have not convinced you, here are some other points to consider:

  • “Pain points” - do you have existing problems or annoyances that you would like to remove? Consider whether the “who, what, when or where” knowledge that is provided by RFID can help.

  • Data-driven decisions - do you feel like you are sometimes “shooting from the hip” in your decision-making process? The data provided by RFID may be able to help. For example, if your RFID tracking shows a particular machine is a bottleneck, you may be able to improve the machine, process or training.


Work-in-process applications provide valuable insights into the operations of your business. They can help you establish key performance indicators (KPIs), which in turn help you know where to focus on process improvements and training. When combined with an inventory tracking system, you get a complete picture of your inventory turns, value, returns and other key data on your operations.

The TallyFlow RFID tracking solution from SDG Systems implements much of the functionality discussed in this article. We can integrate with your other systems. Contact us to learn more about how TallyFlow can help with your WIP, inventory or other tracking needs.

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