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About the Author

Cliff Holste is Supply Chain Digest's Material Handling Editor. With more than 30 years experience in designing and implementing material handling and order picking systems in distribution, Holste has worked with dozens of large and smaller companies to improve distribution performance.

Logistics News

By Cliff Holste

April 22, 2015



Logistics News: Sorting System Optimization Requires Finding The Proper Balance Between Automated Diverts & Manual Palletizing Positions

Optimizing the Number of Diverts with the Number of Pallet Build Positions Reduces Incremental Labor and Increases Overall System Productivity


Holste Says:

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The two key business requirements that must be satisfied are customer orders and palletizing positions.
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Previous Columns by Cliff Holste

Logistics News : Growing Economy Drives Investment In Automation Projects

Logistics News : How to Avoid Losing 4 Months of Non-Productive Labor Per Year

Logistics News : Understanding Expedited Deliver Services Impact on DC Workers

Logistics News : Reducing DC Operating Costs thru the Adoption of Automation Technologies

Logistics News : Calculating Inventory Levels Complicated By Shorter Product Life Cycles

More

Building a mixed SKU pallet load at the end of a shipping sorter divert lane is a labor intensive operation under the best of conditions. A major throughput factor is the rate at which a person can manually sort and palletize mixed SKU cases off the end of a divert lane. For example: if there is just one pallet position, that rate would be much higher than if you have to scan and sort to multiple pallet positions. However, this arrangement (no manual sorting) only works when each divert is dedicated to one discrete order per picking cycle (or batch) and consists of multiple pallet loads for the same consignee.

The two key business requirements that must be satisfied are customer orders and palletizing positions. The sorting system must be capable of processing a given number of orders per day and pallet builds per day to satisfy sales and/or production demand. This can be achieved by having more diverts with fewer palletizing positions per divert, or fewer diverts each with more palletizing positions per divert. The tradeoffs are incremental labor cost verses material handling equipment/system cost.

Manual palletizing productivity declines dramatically as the number of palletizing positions increases, because: (a) it takes more time to determine which pallet the carton goes onto (even when supported by auto ID technologies), and (b) the more pallet positions the more cycle time walking back and forth while building each pallet load and the greater the potential for errors and injuries. In additional each divert position increases the length and cost of the sortation system.

All that said the number of diverts is also based on such factors as:


  • Number of orders per batch
  • Number of batches per day
  • Number of pallets per order
  • Number of cases per order

System planners need to find the right balance between initial system investment and incremental labor cost. The cost of the physical sorter is a onetime capital investment; whereas labor is incremental and on-going. This favors more diverts with fewer palletizing positions per divert. Typically, the number of palletizing positions per divert will be in a range of 1 to 6 with 3 being a good compromise. Facility and operational requirements may place limits on the number of diverts or the length of the sorter. Available funding may also place limits on the size and configuration of the sorter.


Final Thoughts

No matter how efficient batch-order picking and sorting system are what happens in palletizing impacts directly on overall system productivity. Coming up with the best ratio of diverts to pallet build positions involves many variables and in the final analysis, there may not be a “correct” mathematical answer. Therefore, it’s a good idea to allow for some flexibility.

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