Warehouse execution systems sit between warehouse management and traditional control layers in today’s DC software stack, but WES is more than a visibility layer. Using rules engines and order release logic that assesses multiple factors, WES offers smarter, more productive order fulfillment centers.

As more warehouses add automation, using technologies like automated storage and retrieval systems (AS/RS), robotics, and conveyor and sortation systems along with manually focused processes, the need for a relatively new type of software to coordinate all these resources has arisen: the warehouse execution system (WES).

WES is catching on because it can coordinate resources around incoming orders with full knowledge of the availability of automation resources. And, perhaps the best sign of the demand for WES is that more warehouse management system (WMS) vendors are building up WES offerings of their own.

WES sits between traditional WMS and the warehouse control system (WCS) layer that runs automated materials handling equipment on the warehouse floor. The overall role of WES is “orchestrating” the release of work to resources and doing it in a way that hits shipment times while level loading across subsystems to avoid bottlenecks.

“You can think of WES as the central hub of information for a warehouse. WES is constantly getting data flowing up from controls, coming in from the subsystems it interfaces to, as well as information coming down from WMS. We use that data and information to create a balance across the building and a continuous flow of product. The goal is to always have work in front of resources and operators, but never overrun an area with too much work.”

The value of WES, however, is multi-faceted. It’s an over-simplification to say that WES acts like a “conductor” for fulfillment centers. To fully understand WES, it’s best to dig a little deeper.

WES handles order release and “waves” differently than most WMS solutions, using software-based rules engines to make decisions on how to route and balance work. It’s also important to note that WES isn’t the domain of just a few best-of-breed vendors: major warehouse automation vendors also offer WES, and several WMS providers have built it into their offerings. Here are a few ways WES is changing the game.

Smarter order release

Traditional WMS lacks the real-time visibility into the availability of automated materials handling equipment that a WES brings to the table. That visibility and associated rules engines are at the heart of how these systems orchestrate work to achieve a more productive operation.

“WES is doing that intelligent order release to decide which are the best orders and work to release right now, based on the real-time conditions in all the subsystems in all of the downstream processing areas,” says Santich.

The rules in WES should be configurable to allow the system to make smart decisions about which resources in the current order pool to release work to.

WES considers order priority and carrier cut off times, but the rules may also know which subsystems can accommodate special handling requirements, like which pack-out lines have the right consumables to pack up orders that use certain sized cartons or gift wrapping, or that have a shrink-wrap machine to add privacy wrap. WES does this in the background, on a constant basis.

“There a number of different checks the software is doing as part of intelligent order release.

A WES solution’s ability to orchestrate a warehouse is closely tied to how effective its order and work release functionality.

“When you boil it down, Order Streaming helps determine which orders I take action on, and when I release the work associated with those orders, and which resources I release the work to in order to drive the most efficiency in the warehouse”.

Follow the rules

WES features can vary widely. Some vendors have modules to manage capabilities like voice picking or pick-to-light, but at a high level, WES vendors will typically have some type of rules engine for deciding how to release work against the current order pool.

“The WES needs to be able to factor in multiple variables, including order priority, optimization opportunities, including inventory and resource availability, carrier cutoff times, and other capacities and constraints. “That is where a dynamic rules engine comes in, by being able to assess all those variables, and allowing these decisions to be made automatically.”

WES isn’t just for assigning work to automation. A good WES should be able to allocate work to manual processes, like associates picking items to a cart. This is often necessary if order lines that need to be shipped out can’t fit into an automated system, or the automation is currently too full to release more to.

“We also believe that WES can play a very strong role in managing non-automated processes, as well as automated systems”.

Fulfilling e-commerce orders is especially complex because of the order variability involved, but WES makes it possible to instantly find efficiencies against available resources, while accommodating order demand as it comes in rather than in large batches of work that have to fully processed before accommodating additional new orders.

“An e-commerce fulfillment center is very much like a manufacturing production line,” Eldred says. “Only, you’re not making a car, you’re manufacturing orders, and the difficulty there is that practically no two orders are alike. As a result, there is a high amount of sequencing of work in efficiently managing that ‘manufacturing’ of an e-commerce order, which is what WES addresses.”

Pull, don’t push

Rather than planning out large batches of work and pushing them onto the floor, WES uses a pull-based methodology to process orders in a continuous fashion. The picking engine in a WES constantly assess order priority and shipment times, as well as resource availability, in deciding how to release work.

“WES is optimizing for efficiency, but it’s also optimizing for expediency. The picking engine will seamlessly make those decisions and strike the right balance.”

WES’s role in fulfillment centers

A WES seeks to create level flow for an operation, but it can still group work for efficiencies, or to make best use of an automated resource like a putwall by sending it the correct items and work that allow the putwall to turn rapidly, notes Gilmore.

While a WES can support continuous order release, a WES may sometimes devise small batches to find efficiencies, especially with putwall systems. Typically, in large direct-to-consumer fulfillment operations, the WES is continously looking for some type of batch and sort efficiencies.

Automate decision making

Because a good WES is “always on” in terms of knowing resource availability and the progress of work on the floor, its order release logic will automatically avoid bottlenecks. The result of this, is that managers in fulfillment centers can let the WES make crucial decisions that impact the flow of the warehouse, rather than trying to figure it out on their own by looking at multiple user interfaces or data.

“With WMS, a lot of manual decision-making is involved, with supervisors looking at screens and trying to figure out what to do next, and that becomes problematic. For one thing, a computer is always going to assess more factors better than a human can, and second, when you have to rely on human decision-making, it adds latency to the process.”

It does take some effort to configure a WES, but once this is done, key decisions around order release and balancing the resources in the building can be automatic, which leads to a “smart warehouse” outcome, says Gilmore.

“If there is a bottleneck starting to form in one area, the WES is going to slow the release of work into that resource and will recognize alternate paths and resources that can be used”.

Kline notes that with increasing use of advanced goods-to-person automation, a key WES benefit is that it can maximize throughput from those high-end investments, while still being able to route some work to more manual methods. “In theory, your automated resources are going to be more efficient and less expensive than a manual flow, so the ideal situation is to highly utilize the automation whenever that makes sense, and the spillover goes to a manual workflow”. “That is part of orchestration.”

Is WES a must?

There is no simple answer to when companies need a WES, either from a WMS vendor or in the form of a third-party WES. Even though some of the major WMS vendors have made strides with embedded WES during the last couple of years, the need for WES tends to be company specific, and may even vary by site, he adds, with some companies able to get by with WMS and some controls integration.

“The need for WES is going to depend on what they have in terms of current WMS and WCS capabilities, on the current level of automation and their plans for more automation, and on core factors like their order profile and how that is changing, and issues like shipping cut-off times. “It ultimately comes back to whether what they have today is working well enough for them.”

While not all WMS providers offer WES, more have added some capabilities. As a result, for some companies, WES may be more about configuring and turning on what is available from a WMS provider.

“Today much more automation is being used in warehouses, whether in the form of conveyors, sortation, automated storage and retrieval systems, or mobile robots. “There are also more operations doing omni-channel, so the complexity of running a DC increases and as a result, makes it more challenging for the WMS solutions to support all these automated components.”

“The system is able to manage all warehouse resources, the manual workflows, the robots, and the fixed automation with one task-control engine, and with the objective of synchronizing all these resources to execute on time. The main benefit is to have it all—both the WMS and the WES functions—running on a single platform.”

Whatever path is chosen—turning to a WMS vendor, an automation partner, or a WES specialist—WES is likely to be in the future for more companies as service-level commitments increase, and more automation is deployed. That should help companies get more from their automation spend, and from manual processes.

“When WES is done well, you’re going to be able to get more throughput for a given unit of automation. You can either buy less automation to achieve your throughput goal or get more throughput out of the same amount of automation. I don’t think companies are yet factoring in what is possible with WES.”