Just when you need it the most, your material handling system chokes on the heavy volume demands of the peak season. While there can be several contributing factors, the most likely one is that current seasonal volumes exceed the order picking and case handling capacity for which the system was designed. This is a good news/bad news situation. The good news is that your business has been steadily growing. The bad news is that you may have outgrown your current systems throughput capacity.

The result is that your material handling system has a few deficiencies relative to processing current volumes. Perhaps this can be attributed to not having enough pick belts or accumulation conveyor, or maybe the sorter needs to have more throughput capacity and/or more divert lanes? Peak volume periods can just make matters worse. It’s kind of like the leaky roof that leaks only when there’s a downpour.

Upgrading an existing system is a challenge requiring creative thinking and ingenuity if any real improvement is to be realized without major disruption to on-going business.

Keep an Open Mind and Think Creatively

When productivity drops and you suspect a material handling system throughput problem, start your analysis by examining the total picture. In other words understand what capacity the current system is capable of delivering compared to what is needed.

The case per minute rate of a material handling system is dependent on the slowest speed mainline conveyor. In a batch picking and sorting system, this is usually going to be the metering belt conveyor (also referred to as the induction conveyor) located in the mainline feeding the shipping sorter. This particular conveyor is typically located just upstream of the sortation conveyor and is usually fed by one or more accumulation conveyor line(s).

The function of the metering/induction conveyor is to insure that there is sufficient space between cases so that the sorter can divert individual cases into shipping lines. The slow speed side of this conveyor determines the maximum case feet per minute the system can produce. For example if the speed is 60 feet per minute (FPM) then it will handle (60) 12-inch long cases per minute; (45) 18-inch long cases per minute; and (30) 24-inch long cases per minute.

Once you determine the length of the average case, based on the speed of the metering belt, you can calculate what the system is capable of delivering. If that amount is more than what you need, the problem is not with the sorting system. You need to do a more in-depth analysis, such as:

• Assemble pertinent data relative to current system processing capacity.
• Analyze the data against forecasted volume projections.
• Study, develop and implement fixes where needed to eliminate bottlenecks.
• Develop and put in place operational upgrades such as a new Warehouse Control System.
• Evaluate results against needs.

Some problems appear to be obvious and easily fixed such as increasing the amount of accumulation conveyor between picking and sorting operations to smooth out the surges without shutting down picking. However, while this relatively costly approach may provide some temporary relief, it may not fix the underlining system problem.

Digging deeper will sometimes reveal the hidden or less obvious problems that sap system performance.

A good example of this can often be found at the central merge. Here cases of product from multiple picking lines are buffered and automatically merged into a single conveyor line that feeds product to the induction conveyor and on to the sorter. Even when the merge is operating at peak performance, the gaps between slugs of cases being released from the accumulation lines can reduce system throughput capacity by 10 to 15 percent. Installing new merge logic can reduce the gap between slugs from the typical 3 to 5 feet to just a few inches regardless of line release sequence. I have seen this merge control logic in operation and I found it fascinating to watch. Your system provider can advise if this control upgrade would be applicable in your operation.

Final Thoughts

No doubt there are a lot of companies, both large and small looking for the telltale signs of economic recovery. They are considering improving the performance of their current logistics operations to give them a competitive advantage going forward into the next robust business cycle. For these companies it is important that they quickly put into place a planning model that ensures success.

Agree or disagree with Holste's perspective? What would you add? Let us know your thoughts for publication in the SCDigest newsletter Feedback section, and on the website. Upon request, comments will be posted with the respondent's name or company withheld.

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