right_division Green SCM Distribution
Bookmark us
SCDigest Logo

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

July 9, 2014

Mixed SKU Pallet Loads Speeds Product Restocking At The Store

Technology Solves Complex Mixed Product Stacking Requirements

Holste Says:

The benefits of building store specific loads include significant labor savings and improved operational efficiencies at the store level.
What Do You Say?

Click Here to Send Us Your Comments
Click Here to See Reader Feedback

Previous Columns by Cliff Holste

Sorting It Out: Shippers Looking To Increase System Capacity Are Surprised To Find It May Already Exist!

Sorting It Out: For Shippers - Benefits Of Real-Time Control In The DC Are Huge!

Sorting It Out: Shippers Looking to Improve Operations Choose Customer Centric Approach

Sorting It Out: Productivity is a Crucial Factor in Measuring Production Performance

Sorting It Out: Packaging Construction Impacts on Logistics Operations


One of retailer’s most challenging goals has been providing practical solutions for building store specific mixed SKU unit loads. The challenge for the DC becomes even more difficult when trying to build mixed SKU loads that are also optimized by aisle and product location within the aisle. It has been estimated that when combined with specific pallet building rules there are over a million different combinations of variables that can come into play.

The benefits of building store specific loads include significant labor savings and improved operational efficiencies at the store level. However, constructing this type of load at the DC is nearly impossible to do requiring a high level of material handling automation and sophisticated order fulfillment software. While the cost tradeoffs for mixed SKU palletizing may not yet be clearly defined or understood, assuming labor cost in the DC continue to increase, most companies will be looking to adopt more automated methods for palletizing. The ability to provide store specific mixed SKU loads will further enhance their VAS offering.

Given the broad range of emerging material handling technologies, coupled with blazing fast and relatively cheap computer power, the industry seems poised to deploy practical solutions that solve the mixed SKU palletizing enigma in a variety of cost effective ways.

The Sequencing Solution

The concept of product sequencing actually has its roots in the auto industry where they perfected sequencing of parts for their assembly operations. The assembly plant orders specific items from internal parts depots and/or direct from suppliers requiring that they are delivered just-in-time and in the precise sequence needed on the assembly line.

Mixed SKU palletizing usually involves some type of short term case storage module of sufficient size to hold the customer’s order, such as a Mini-Load ASRS, coupled with an automatic stacking machine, such as a robotic palletizer. The key to linking the “sequencing” of the cases out of the storage module into the pallet build station is the software system sometimes referred to as “Best-fitting Software”. This software performs like a 3D puzzle in figuring out how individual cases need to go together to build pallet loads.

In any individual customer/store order, for safety and practical reasons, not all products or cartons are stackable. The software is choosing product stacking suitability and sequence according to various attributes such as:

  • Shape and dimensions of cases;
  • Packaging type;
  • Product communality;
  • Stacking ability (configuration, weight, nesting, fragility, etc.);
  • Route sequence; (store aisle and shelf location)
  • Volume saving;
  • Stability of the load.

The software also supports many different modes of palletizing:

  • Interleaved or interlocking;
  • Column stacked;
  • Hollow center core and/or chimney stacked, etc…

Building mixed SKU pallet loads depends on being able to pick, stage, and sequence the delivery of product to the pallet build station. The first step is to build a virtual pallet load. Once completed, a 3D view can be provided for approval or modification.

The output case rate of the storage module needs to be in-sync with the input rate of the palletizing operation. Therefore, no buffering is required between storage and palletizing allowing the two operations to be closely coupled.

Automatic palletizing can be accomplished with either robotic arm or gantry type equipment depending on carton handling characteristics, operational, and system layout requirements.

Another option is to utilize an ergonomically designed semi-automated manual palletizing station. The same software is used as described above except a large flat screen monitor displays a 3D view of the pallet load and where each case needs to be placed.

The small percentage of cases that for whatever reasons cannot be handled within the automated system, can be processed manually and placed on a special pallet or placed on top of a previously palletized load.

Once the pallet build operation is completed the palletized loads are typically transported to a centralized automatic stretch wrapping machine. The conveyors used for transporting the unwrapped loads are specially designed to provide for gentle and smooth handling. In applications where pallet load stability is a major issue, the load can be automatically stretch wrapped in the palletizing station as it is being built.

Store Aisle Sequencing at Pep Boys

At Pep Boys products are stored in pick modules within its DCs in family groups containing like items. They say that this makes order fulfillment more efficient and improves slotting in the pick modules. Items in the Pep Boys retail stores are arrange in the same family groups as in the DC, with similar products shelved together. At the DC items are manually picked, palletized, wrapped, loaded and shipped as close to store aisle putaway sequence as is possible.

Assignments for order selection are generated by the host WMS and transmitted via wireless network to the appropriate worker. A Vocollect Voice application translates the assignment into speech commands that direct a worker to an aisle/section and slot location.

Pep Boys reported a few years ago that this method saves them 35 man hours per delivery. If each store gets 2 deliveries per week, their saving 70 hours/store/week – a huge savings when accumulated across their network of stores. In addition, backroom congestion has been improved and product damage reduced.

In addition to reducing restocking time once product arrives at the store, aisle specific palletizing lessens backroom congestion and promotes safe handling practices reducing injury and product damage. For these reasons, and many others, large retail operations, especially in grocery and beverage, are among the early adopters of this technology.

Final Thoughts

One of the key technologies driving DC automation today is the ability to build mixed SKU pallet loads. This has been a long anticipated development that will continue to evolve and grow. Why? Because retail store managers want it, and because in our current society, with few exception, it’s becoming increasing difficult and expensive to hire workers for this kind of back-breaking, mind-numbing task, especially in a warehouse environment.


Recent Feedback

This is an interesting article to highlight the complexities retailers face.  We deal with many large chains and find the outbound labeling function is greatly improved if done while the load is being constructed item by item at the site of the work.

Kevin Ledversis
Sales Manager
Newcastle Systems
Jul, 26 2014

 It's been a while since this article was written, but we at System Logistics completely agree on the benefit of mixed SKU pallet loads and have developed an automated system to build the loads.

Alfredo Valadez
Sr. Director
System Logistics
Apr, 20 2016