Maintain material traceability in LMS-commissioned plants
Introducing manual processes in line management systems (LMS)-commissioned plants can harm material traceability
Warehouse space allocation is a fundamental aspect of any manufacturing facility. By necessity, optimizing space accessibility and maximizing it to store raw materials, work-in-progress (WIP) materials and finished goods is an ongoing and primary focus at manufacturing plants across various industries. Some plants may try to address their space constraints by moving materials to other locations within the plant. But for plants that are fully commissioned with line management systems (LMS), these attempts to optimize space must consider whether the warehouse management system in the proposed new location can communicate with the LMS.
Moving materials to storage locations outside the boundaries of the LMS raises the risk of losing their traceability, which is a common pitfall when the plant is using a manual retrieval/put-away process in addition to its LMS. The International Organization for Standardization (ISO) defines traceability in ISO 9000 as “the ability to trace the history, application, use and location of an item or its characteristics through recorded identification data.” Certain strategies can help mitigate that risk.
What might motivate an LMS-commissioned plant to alter its material storage locations, and in doing so, eliminate the use of automated guided vehicles (AGVs) for retrieval and put-away of the associated materials?
A common motivation is the desire to use first in, first out (FIFO), which is typically incompatible with warehouse management systems connected to LMS. The FIFO method is an inventory management concept in which the oldest stock is used first. In an LMS-commissioned plant using AGVs, the AGVs do not typically pick up products on a FIFO basis. If the plant prefers to implement FIFO, but their warehouse management system does not support it, one strategy is to use a storage location without AGVs and use manual forklifts instead.
Recognize the risk in AGVs versus manual systems
An LMS-commissioned plant that uses manual forklifts for material retrieval risks losing the material traceability provided by LMS when using AGVs. The warehouse management system on which AGVs operate communicates with LMS as material is moved across sub-inventories, for example, as in a sub-inventory transfer (i.e., a raw material sub-inventory to a WIP sub-inventory). Without AGVs, the plant loses the integration between LMS and the warehouse management system for those vehicles, thus necessitating an alternate procedure for the sub-inventory transfer. This typically entails a manual sub-inventory transfer process, which requires the forklift operator to scan the barcode on the container label and virtually “move” the container to the sub-inventory destination by scanning another barcode on a sheet of paper, which represents the destination for the sub-inventory (see Figure 1).
To ensure accurate material traceability, LMS must be able to discriminate between each container of raw and WIP materials consumed at the production line. This is done by assigning a unique identifier to each container: typically, an alphanumeric code printed on a label affixed on the container. These labels are applied by an operator whenever a full container of material is produced at a WIP material production station, or by a receiving associate upon the material’s inbound delivery to the plant.
Each container label printed via LMS software receives a unique identifier in its barcode. However, container labels printed outside the LMS software have barcodes that read something else — namely, the item, lot and quantity details used to perform a manual sub-inventory transfer. Thus, there are two different label types (with and without a unique identifier) for the two different sub-inventory transfer processes (LMS and manual). Therefore, in the effort to optimize warehouse space, an LMS-commissioned plant that eliminates AGVs in favor of manual forklifts will lose traceability in the LMS for related materials.
How to restore materials traceability with a manual process
Two strategies can help manufacturing plants rectify the traceability problem that results from using a manual process:
- Reformat the LMS-generated label so that it contains both the unique identifier in its barcode, and encode the item, lot and quantity data into a QR code on the same label (see Figure 2). The label thus becomes multi-purpose, retaining both features necessary for material traceability and manual sub-inventory transfer.
- Use the LMS-generated label in its original format, as shown in Figure 3, but require the forklift operator to manually enter the details for sub-inventory transfer through a keyboard attached to a small, fixed-mount computer connected to the inventory software. Circumventing the scanning step would mean that the barcode on the label does not need to contain the item, lot and quantity data. The forklift operator would instead read that information from the text printed on the label to perform the manual sub-inventory transfer.
Each of these strategies comes with unique caveats. In the latter scenario, a manual sub-inventory transfer becomes a much more involved process for the forklift operator, and it introduces the risk of mistyping the quantity or lot number for the given material when entering the data. In the former scenario, manufacturing facilities that are part of a larger network of plants (e.g., a company with nationwide operations) might face difficulties in adhering to standardization policies and practices. Changing the label format at one plant might impact the ability of another plant within the company to integrate those material containers within their own warehouse management systems if they are shipped over to support operations at the second plant.
If an LMS-commissioned plant seeks to optimize warehouse space by altering its storage locations, ensuring that the new locations are mapped within the boundaries of the warehouse management system (which communicates with LMS) will help avoid loss of material traceability. If the objective is to implement a FIFO method, the LMS-commissioned plant should use AGVs on a warehouse management system platform explicitly designed to accommodate FIFO, so there is no need for manual sub-inventory transfers or forklifts.
Losing the ability to automatically trace materials can delay production, require unplanned expenditures for replacement materials, damage customer relationships and ultimately impact a manufacturer’s bottom line. In the event of an audit, robust material traceability provides a valuable functionality that allows for determining the source of a defect anywhere along a product’s lifecycle. Because manufacturers must be able to minimize downtime and constraints on plant personnel, maintaining material traceability is paramount, and should be a focal point in any attempt to optimize warehouse space.
Oladeji Andrew is a manufacturing technology lead project engineer at Niagara Bottling LLC, the leading manufacturer of private label bottled water in the U.S. He specializes in leading-edge composite plastic materials fabrication and LMS commissioning and troubleshooting, supporting existing LMS systems and developing new LMS installations at multiple Niagara Bottling plants across the U.S. Among his broad equipment and engineering responsibilities, including design, application and process improvement, Andrew is applying his expertise in production line automation, track and trace, material management and order management in his oversight of a four-line LMS commissioning project that is one of the company’s largest plant installations.