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From SCDigest's On-Target E-Magazine

- Nov. 18, 2014 -

Supply Chain News: High Speed Sortation Systems - Does WMS Often Have a Hard Time Keeping Up?

Real Issue or DC Urban Myth? Not Enough Validation Testing is Done to Catch the Problem Early, Mark Fralick Says

SCDigest Editorial Staff

In a high speed sortation system in distribution, the integration between the Warehouse Management System (WMS) and some form of Warehouse Control System (WCS) is obviously key to system success. The WCS is the direct interface to the sortation system and control diverts, merges, etc., based on instructions from the WMS (although there are different flavors of which system does what).

This integration has historically been a challenging task, however, for a variety of reasons. There are generally at least two and maybe three or four parties in the mix: WMS provider, WCS provider, sortation system provider (if different from the WCS company), and maybe a consultant or two to boot. That just means there are often a lot of different companies that must come together to design and execute the integration plan.

SCDigest Says:

"The key is that some sort of functional testing that emulates production volumes simply must be in the project plan," Fralick adds.

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This integration has also often required some level of customization on the WMS side and often the WCS as well, and that usually means risk. While the integration approach has to an extent become much more standard, it is also fair to say in general each one is a little different and certainly not "off the shelf."

With regard to WMS-WCS/sortation integration, there are two big blocks of things that need to be work almost perfectly: (1) the right messages are being sent by the WMS to the WCS, which is receiving them and sending back the right confirmations; and (2) that this message dialog is happening fast enough to enable to system to work at the level that was designed.

Here, we are going to focus on the second of those two issues: can the WMS keep up? That question, of course, is being posed as the speed requirements keep advancing, with conveyor-based sorters now pushing 700 feet per minute, and tilt tray sorter operating near the 1000 fpm range.

On the positive side, computing power and speed keep advancing, which is an important element in the performance mix. One would also assume that WMS providers are improving their own system performance all the time, so that should also reduce response time issues as well.

Yet, SCDigest continues to hear anecdotal evidence that in a number of implementations, still here right now in 2014, sortation companies are turning down the speeds at which their systems are running because of WMS response time issues. And that is a big deal: it means a given system/facility will have lower carton throughput than should be possible, and/or that the company could have installed a somewhat smaller, less expensive sorter than is required to get the throughput needed when it is operated at lower than maximum speed.

So is this scenario really being experienced, or is it something more of an "urban distribution myth?" Jim Barnes, managing partner at enVista, a consulting and integration company that has a lot of experience with sortation systems, especially in retail, thinks it often comes down to a battle of sorts between sortation system/WCS provider and the WMS provider.

"It's important to understand that total system performance starts with the system design and how best to leverage each technology - WMS and WCS - to achieve the most efficient and effective facility performance. Unfortunately very few companies and resources have deep domain expertise in both. Therein lies the problem," Barnes told SCDigest. "If I only know what a WMS does or visa versa I only bring a WCS to the table, then I am going to implement a solution with a bias."

Barnes said he finds that many WMS and WCS software providers increasingly cross each other's areas of technical core competence.

"I would ask the question: Why is a WMS trying to control any piece of automation? Where speed is an issue it is usually is where the WMS was implemented to manage a piece of automation - not a good idea," Barnes says.

As a better approach, Barnes cites the example of a recent pick- and put-to-light solution that enVista helped to implement, in which the WMS only manages the allocation of inventory at a zone level. The WCS dynamically allocates inventory to multiple locations because it is managing the balance of where each carton is picked from in real time (a SKU can be slotted in multiple locations). When the picks and carton are complete, the WCS sends a message back to the WMS.

"In summary, it starts with leveraging the capabilities of what each solution does best," Banres said.

"This question in general assumes that the WMS needs data back from the WCS, which normally controls the I/O. In terms of sending data from WMS to WCS, most WMS software now use sockets interfaces that are fast enough," Barnes told SCDigest. "We have witnessed many automation companies make strong cases that the customer does not need a WMS. I would argue that you need to understand the flow of inventory and how orders are going to be processes and ultimately how and where inventory will be managed and allocated first."

One Expert Says the Issue is Very Real

Mark Fralick, CEO of WMS implementation and technology company GetUsROI, has been a leading player in the Warehouse Management space for almost 25 years. He believes WMS response time problems actually continue to manifest themselves quite often.

"Yes, unfortunately the problem is quite common," Fralick tells SCDigest. "Fast to one person is not the same as fast to another. For the WCS crowd, time often relates to feet per minute. So, they have very finite limits when it comes to time. If you miss the window, you will cause a recirc, which impacts the overall throughput of the operation."

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He adds that "The WMS vendors, in large part, have lost the concept of fast. Unfortunately, the 'time' thing has become a bit compromised as they've layered more, albeit valuable, functionality on to their systems. So: fast, how fast and what it means need to be something the integration partners need to agree on very early in the design process."

Fralick, in fact, says that the way this integration is now often implemented actually has reduced communication speeds. Instead of a direct messaging interface between WMS and WCS, as was traditionally the case, he says many WMS providers now insulate themselves with a web services layer or a separate integration layer that causes extra overhead and may not allow the 'time' problem to be solved without some creative alternatives - which the WMS vendor is not often happy about employing, he adds.

How Can Shippers Protect Themselves?

As noted above, delays in WMS-WCS communications can have a meaningful impact on system performance. At its worst, it can mean the system has real operational issues that significantly impact DC processing.

More often, it means the conveyors have to be run at slower speeds, or with greater spacing between cartons on the sorter, either of which degrades real throughput.

Catching and Solving the Issue Early

So how can shippers work to avoid this fate for their new sortation system? First, they have to ensure all parties - WMS provider, sortation provider, etc. - have signed up to the level of performance before the contracts are approved. Sometimes, these details are perhaps surprisingly a little bit fuzzy.

Second, success requires a deep level of testing before system go live, or what Fralick refers to as "validation" tests, which will demonstrate the system can keep up with expected volumes at design speeds. Surprisingly, Fralick says such validation testing often is skipped, or performed very loosely, and so it is not until conveyor volumes really ramp up that anyone knows if there are issues or not.

Fralick acknowledges that doing this level of validation testing can be difficult - but is far from impossible.
In his projects, for example, he says his company always builds emulators so that by the time the equipment is ready for testing, they already have tested thousands and thousands of records and performed volume/speed validation on the WMS side as part of that process.

Too many WMS project teams do not allot time for this, Fralick says. "Then when it comes time to test, they too often only do 'happy path' tests like "Hey, let's put a few boxes on and see if they end up in the right spot. The problem comes down to allotting time and budget in the project for real-life testing at scale."

He cites a recent example, where his team asked for data on the peak belt volumes expected (number of cases on the sorter at one time) and for how long that peak would last (is the peak for 3 hours, 5 hours, etc.?). Get US ROI then ran tests against 50, 80, 100, and 120% of these numbers over a series of nights to ensure the response time was adequate.

Fralick says that "Unfortunately, this level of testing is rarely done," though he notes sometimes that testing is actually not necessary if the peaks are not pushing belt volumes.

"The key is that some sort of functional testing that emulates production volumes simply must be in the project plan," Fralick adds. "The problem is that most WMS project teams overlook this and when pushed don't want to do it because it will blow the budget. It is a pay me now or pay me later proposition."

Seeing performance levels at these peak volumes needs to be defined as part of the acceptance testing requirements put into the contract, he says. Too often companies sign off before that level of volume is actually seen, he says, because it can often take months to reach peak system volumes.

Have you seen issues with WMS response times keeping up with sortation speeds? Is more validation testing needed? Let us know your thoughts at the Feedback button (email) or section (web form) below.

Recent Feedback

Very good article about the response time between WMS & WCS. I agree that validation testing is not performed before the Go-Live. The problem is during the dry run test of WCS with WMS in the test server, we don't get the real peak volume data. This is again an important factor, when every WMS team cannot focus on real testing with peak volume.

Prabhu
WMS Vs WCS
GSL
Nov, 24 2014