What, exactly, is waveless picking? To understand it, advocates say, you have to let go of the operational mindset built on waves of orders released in sequence to the material handling system.
Think of it, instead, as a way of releasing individual orders to the system based on downstream availability of capacity—a technique that pulls orders into the system discretely rather than pushing them in batches. A wave of one, as one believer describes it.
Think of it, too, as conceptually aligned with the idea of demand-driven execution. That idea, which has been around for a while, continues to gain adherents as the enabling technology catches up with the theory.
"Waveless is a microcosm of demand-driven fulfillment or execution," says John Fontanella, vice president of research for AMR Research. Fontanella has been beating the drum for demand-driven strategies for several years. He sees demand-driven fulfillment as part of what he calls the fourth stage in the evolution of supply chains. In the first, businesses react to orders as they arrive. In the second, they use forecasting and demand planning tools to anticipate business. With the third stage comes collaboration with business partners.And fourth is the stage he calls "synchronization.""You control your own operations and those of your partners," Fontanella says. Clear insight and understanding of downstream demand allow upstream managers to align business with those demands.
What has that to do with warehouse operations? "Many warehouses just react without understanding the world outside the walls," Fontanella asserts. But waveless operations are all about synchronizing operations with demand and capacity. Dan Perry, a senior systems engineer for VARGO Adaptive Software LLC, describes the shift from using waves to a waveless operation this way: "It is how to turn a facility that uses cycles to one that uses flows."
Waveless systems operate, their advocates say, by adding a layer of intelligence between the warehouse management system, which releases orders to the material handling system, and the warehouse control system, which manages the system. That, Fontanella explains, allows the overall operation to look for what is the top priority at the moment— and to shift priorities on the fly.
Yet it's that "middleware" that's often the sticking point. It is not cheap, and implementation normally requires the IT department's cooperation. Shifting to waveless is more complex than changing WMS code and operational tactics. But its advocates claim it can pay off in a big way by increasing throughput and operational efficiency; improving labor productivity; reducing exceptions; reducing, if not eliminating, buffers; and, in many cases, avoiding capital expenditures.
The law of inertia
Despite its reputed benefits, waveless isn't always an easy sell. The first barrier to implementing waveless picking may simply be one of education and persuasion. Any major shift in operations includes an element of risk, and managers have to be sure that the risk is worth it.
Second, it does require some significant programming.
Says Marc Austin, a senior account executive with Fortna, "There's a large level IT involvement in this. That's because waveless requires installing optimization software that sits between the warehouse management system and the machine and equipment controls. That's a constraint for most companies. Companies like ours can handle a lot of that, but we still need to work with the existing systems. It is tough to get the resources at times."
Perry says that companies are often reluctant to add another piece to the system. Furthermore, the computing power and enabling software tools are a relatively recent development. "It was not possible until recently," he says. "It is a realtime computing effort. It is actually making a decision on what to do next every time a worker finishes something. You have to dynamically calculate everything."
Bob Carver, vice president of VARGO, adds that often, IT professionals don't understand the reality of operations. "IT comes in with the perspective that you can develop the perfect plan," he says. "Operations are at the other end of the spectrum. They need to get stuff out the door." Those in IT, he says, tend to see exceptions in the DC as failures by operations to execute the plan; operations people recognize exceptions as inevitable. "They need something adaptive and objective-driven, not plan-driven," he says.
Then there is the mindset. "There also has to be a paradigm shift," Perry says.
"It is a big leap for people,"Austin adds. "It is such a big change; you are not just going to turn the switch and change the environment you are in today. You have to work through the process."
Behind the success
To envision how waveless works, say its proponents, it helps to look first at existing practices. Traditional wave-based systems can handle the bulk of orders quite efficiently. But every wave has its exceptions. And that creates a wave "tail."
If the completion of orders in a wave were shown on a graph, the peak of the wave would be the high point, with orders flowing rapidly, and the tail would be at the end, where all the exceptions are being handled and productivity falls off. The length of that tail can be viewed as a measure of a DC's productivity. In a white paper it produced on wave productivity, VARGO explains that how early an exception is detected and how long it takes to correct directly correlate to the length of the tail. And those tails have a direct, negative effect on DC productivity.
Austin, the Fortna executive, explains, "What we always try to do in a wave environment is a lot of optimizing. We eventually end up pulling the orders with a lot of commonality. But there is still a lot of garbage at the end to deal with. One of the problems with wave optimization is you still have to deal with all the bad somewhere. Everyone runs wide open for 80 percent of the volume, but that last 20 percent can take 50 percent of the time of the wave."
That can leave the DC and its material handling equipment idle while the tail is cleared up. "It's incredible how much equipment is not used all the time," Austin says. "We constantly see equipment used under 50 percent of the time."
By contrast, a waveless system is designed to pull individual orders into the system when resources become available. That, Austin explains, allows managers to maintain an even workflow and keep conveyor systems full while at the same time reducing, or even eliminating, the need for buffers.
It is important to note that waveless systems have no fewer exceptions than wave operations. Says Austin, "If you think you are never going to have exceptions, you are building a system to fail. The question is, when you do have exceptions, how do you deal with those in real time? Can you make sure they affect only the orders they are related to?" Both the Fortna and the VARGO experts are quick to point out that waveless systems are designed to isolate those exceptions, and that they do not affect the overall productivity of the material handling operation.
Ideally, each exception should affect a single order or a small subset of orders. But in a wave-based system, the exception affects the entire wave, Perry says. "In the case of a wave-based system, you need to wait for all the missing items," he explains. "In a waveless system, each order is really a wave—a micro-wave—by itself. It is not waveless at all; it's processing hundreds of waves simultaneously. Each wave includes the items for one particular order." So, when an item is missing from one order, only that order gets delayed. "In the meantime, all the other orders are [being] processed. You are just tying up that one little resource and not holding anything else up with it."
Carver adds, "When you are setting up a plan for the day, the first thing that happens is something goes wrong with the plan. A demand-driven system allows you to work through the ebbs and flows or pick issues, like equipment being down or workers not showing up. We're creating real-time plans that change every second. When we ask 'Would the plan have changed if we had known of the exception beforehand?' the answer is always 'certainly.' Plans are created by objectives. By using real-time techniques, those same objectives can be executed directly, compensating for those unforeseen exceptions."
Austin elaborates: "In waveless, we try to break all the resources apart. Each dock door, each chute becomes a unit of one." Individual orders are released to the system only when the system has capacity to handle them. "It is all about managing sequence. Waves have problems because things get out of sequence."
Waves, he says, are based on pushing orders into the system. "Whenever you push, you don't know if a resource downstream is available. You are just trying to jam work in the funnel." Buffers—accumulation conveyors that hold goods that cannot fit into the current flow—are expensive ways to mask the inability to maintain a sequence, he argues. "The most expensive storage in the world is accumulation conveyors," he adds.
Perry explains further, "As a pull system, queues are dramatically reduced. You are pulling to spaces that have capacity to do processing. If you stop packing, it stops releasing new orders.Why not pull when you need it? That's what waveless does. It is demand driven— looking at the back end, pulling through to fill the demand."
For all the talk of waveless picking's advantages, in the end, what DC managers really want to know is whether it's worth the effort. Austin, for one, insists that it is. "The payback is enormous," he declares. The Fortna executive says he has seen cases where picking efficiency improved by 18 to 20 percent as well as cases in which the operation realized only small gains in picking efficiency but jumps of 30 percent in system capacity through improved utilization.
Perry cites the example of L.L.Bean, the big catalog retailer and a VARGO customer. "L.L.Bean literally increased capacity by over 30 percent," he says. "They were running a sorter for years that was capable of 18,000 sorts an hour, but the best they ever got was about 13,000, and more typically, 11,000."After shifting to a waveless operation, the system began operating close to 18,000 sorts per hour.
Those benefits notwithstanding, waveless is not for everybody. It fits best with mid- to high-volume split-case operations—DCs with 30 or more people working in fulfillment operations, Perry says. "Part of this is the price point," he explains. "You are not going to do any good without an ROI.You are not going to spend half a million dollars without getting a return. You can get between 20 and 30 percent improvement.We would like to push that down, but we are not there now."
As that happens and word of successful waveless implementations spreads, distribution executives are taking note. Austin predicts, "Three years from now, a big chunk of industry will be working this way."