The traditional roles of warehouse management systems (WMS) and warehouse control systems (WCS) were rather straightforward: WMS managed information and controlled inventory, while WCS drove equipment and people.
"As the 'traffic cop' for the warehouse/distribution center, the WCS is responsible for keeping everything running smoothly, maximizing the efficiency of the material handling subsystems and often the activities of the warehouse associates themselves," explains Chris Castaldi, director of business development at Carlstadt, N.J.-based W&H Systems. "It provides a uniform interface to a broad range of material handling equipment such as AS/RS, carousels, conveyor systems, sortation systems, palletizers, etc. The WCS acts as the brain for any automated distribution center, providing communication between the WMS and all the material handling equipment and processes needed to complete an efficient distribution system."
But as WCS has evolved, the line between the two systems has become increasingly blurred, with functions sometimes overlapping. Whereas WCS was once the bridge between the WMS and PLCs initiating automated activity, it has begun to play a larger role in order fulfillment and warehouse management execution.
The Evolution of WCS
Warehouse control systems started out as rudimentary software application layers that were connected to machine controls, be they on a conveyor, a crane, and so on. Typically they were rather thin, single-instance applications sitting on a PC in a warehouse, managing machine transactions. "Over time, WCS has been built out on both sides," explains Ryan Sheehan, CEO of Conshohocken, Pa.-based Invata Intralogistics (Invata).
WCS providers have been looked to as the first line of support for all electromechanical types of equipment in the material handling process as a result of the deep integration of WCS to machine controls via PLCs or outboard processors. "The WCS is the place where you get into a site and diagnose most electromechanical or technology issues," says Sheehan.
Likewise on the higher level, WCS is no longer single PC instance or application layer software—it's enterprise software solutions residing in the server room with all other major enterprise software. It's connected to controllers that are typically deployed on the floor, running localized applications with a machine control, but handling higher-level tasks in terms of taking advantage of inventories in motion at the facility, managing orders and doing allocations, and optimizing the status of equipment at any moment in time.
So a combination of enterprise and marketplace forces has reshaped and broadened the role of WCS, perhaps most significantly the explosion of e-commerce. "This development is driving growth in the WMS and WCS markets," says Clint Reiser, analyst at ARC Advisory Group. "The growth is likely to continue as facilities are reconfiguring and retooling for e-commerce fulfillment. It's almost the singular reason for current growth."
Even before the e-commerce boom, the complexity of distribution and order fulfillment had been increasing. Pallet shipments gave way to cases and split cases; customer requirements have reached unprecedented levels, while management expects higher throughput at faster speeds with better accuracy. All this is occurring in an environment motivated to drive down costs and prices, which has accelerated automation adoption, which in turn has driven use of WCS.
Orchestrating WMS and WCS
According to Sheehan, a facility doesn't necessarily get the best operational results with WCS and WMS sharing functionality, essentially fighting for functional power. "One typically has to be marginalized and subordinate itself to the other in order to make the best decisions at any given moment to shorten the 'length of day' of an operation," he explains. "It just doesn't work well when they're overlapping."
The nature of orchestration is typically driven by the structure of the organization. "If you're a customer with multiple facilities, and they are all slightly different, the WMS that have been around a long time have a great deal of supply chain-type visibility tools and enterprise performance metrics; this isn't necessarily where WCS go," says Sheehan. "So if you have multiple facilities, it's a comfortable thing to have one WMS that is deployed across those facilities and has slightly different modifications to accommodate their differences."
In contrast, if a user is focused on one distribution center and wants it to be totally optimized, with everything designed to reduce labor and shorten orders and move inventory to customers as fast as possible, then the WCS approach is superior because it's so tied into equipment and technology. It can be deployed and engineered for that specific purpose (i.e., as opposed to a product deployed across multiple sites).
Reiser echoes this observation: "The importance has to do with the structure of a warehouse. In a large facility with a lot of automation, like a FedEx DC or an Amazon warehouse/DC, the controls are more important to managing the whole system, so the WCS would take precedence. In a system where there is less automation—with more picking and smaller items—the WMS may be the more critical system."
Balancing the roles of the WMS and WCS is critical. Best practices include utilizing WMS components for functionality that WMS does well, utilizing WCS components for functionality that WCS does well, and minimizing overlap of functionality and data to avoid maintenance in multiple systems and facilitate their working together and not at odds. Sheehan's point about establishing dominant and subordinate systems helps ensure that best practices are realized.
A Tasty Case
Invata leveraged its WCS in implementing a successful distribution center design for snack food manufacturer Old Dutch Foods in Roseville, Minn., doubling the throughput of the previous distribution center operation with just half the labor. The design incorporated warehouse automation technology that included an extensive conveyor system and sortation system with a sliding show sorter and Invata's WCS. They also implemented a product serialization strategy that enabled Old Dutch to track every case of food from the distribution center through in-store delivery.
Four key objectives were defined at the outset:
- Meet efficiency goals by doubling distribution center production with the existing labor force, thereby creating a more streamlined organization.
- Ensure product quality by implementing both lot and serialized control of all SKUs and shipments.
- Eliminate inventory shrinkage through the use of serialized inventory tracking.
- Increase distribution center throughput to process orders and schedule trailers at shorter intervals and with faster turnaround times.
To meet the objectives, Invata developed a DC design that seamlessly receives product from manufacturing and delivers orders directly into waiting trailers. Once the final production operations are complete, cases of manufactured product are moved to the warehouse and staged in a forward pick area. Pallets are staged according to lot, and are serialized for future tracking to ensure first in, first out (FIFO) picking and traceability through the entire manufacturing and distribution process, including delivery to the retail location and, ultimately, the end customer.
The process is initiated when the ERP system host computer organizes orders by truckload in reverse stop sequence, and lanes are assigned by the WCS system. Orders are then batch-picked by generic SKUs and released to RF picking. Cases are promptly loaded onto the shipping conveyor where they are scanned and assigned to specific orders by the WCS, which also assigns the product serial numbers to the order at that time, enabling every case to be tracked to destination. The system enables multiple orders to be processed simultaneously. Once cartons have been sorted (by trailer and route), they are confirmed to the ERP, and physical shipping documents as well as electronic records are transmitted.
Results have been impressive:
- Realizing a leaner and more streamlined DC.
- Doubling production to meet growing demand without expanding staffing.
- Eliminating shrinkage (under the previous system, more than 600 cases per month were shipped in error and lost).
- Increasing throughput dramatically by doubling it in less time than it previously took to ship half the volume.
WCS continues to evolve rapidly. A new breed of WCS solutions—warehouse execution systems (WES)—has recently entered the market. These systems are largely focused on the rapid growth of omni-channel fulfillment and the challenges it poses. The impact of WES in the market remains to be seen, but the solution (as a discrete category) is gathering momentum in the material handling sector.
Based in Asheville, NC, Marty Weil is an award-winning freelance business journalist with more than 25 years of experience writing about manufacturing technology. He can be reached at [email protected]