Understanding how AS/RS and AMR solutions differ from one another is the first step to not only determine which one is best for your organization’s warehouse, but also where their joint use can optimize workstreams and throughput.

By Andy Lockhart, director of strategic engagement, warehouse solutions, North America, at Vanderlande

Consumers’ affinity for online shopping appears to have finally reached an equilibrium where e-commerce growth is in line with expectations. Although macro-economic trends, such as inflation’s impact on consumers’ buying power and capital costs for sellers, continue to raise questions, most believe we have reached a new normal in which the omnichannel shopper reigns supreme.

The United States Census Bureau’s Quarterly Retail E-Commerce Sales Report quantifies the trends.  While consumers continued to enthusiastically frequent the stores they missed four years ago, e-commerce continues to grow. Total estimated retail sales in the fourth quarter of 2023 increased 2.4% from the fourth quarter of 2022, but e-commerce sales increased by an estimated 7.2% in the same period. Online purchases also accounted for 17.1% of all sales versus 14.7% of all sales in the previous year.

Consider the Software

While robotics and singular innovations like AI receive the lion’s share of hype within the warehousing and DC communities, much of the transformative innovation shaping materials handling operations is taking shape at the software layer, a reflection of the fact that numerous automated systems and machines must be integrated and working in concert with one another to maximize efficiency. For this reason software – from task specific applications like the vision software used by robotic pickers to the platforms that tie everything together – should be carefully considered.

In particular, fulfillment operations should look for the hallmarks of robust software.  These include:

(a) User experience and ease of use;
(b) Security; 
(c) Integration capabilities; and 
(d) Support and service.

In light of this, materials handling and fulfillment organizations for U.S. retailers doing business with global brands are actively looking for ways to not only make their operations more efficient, but also to address a wide range of longstanding hurdles. These include the ongoing challenge of attracting and retaining warehouse and distribution center (DC) employees, higher operational costs, demand for faster delivery times, increased throughput and order accuracy; and greater pressure to avoid the bottlenecks that result from manual operations and processes.

As a result, more companies are looking at where to begin their warehouse automation journey or how to refine it, with fulfillment operations offering the greatest opportunities to drive bottom-line and top-line results. Not surprisingly, Automated Storage and Retrieval Systems (AS/RS) and Automated Mobile Robots (AMRs) are key components in these efforts.

Despite this, many organizations struggle to determine which solution is best for their organization, how AS/RS and AMR solutions differ from one another, and where they can collaborate. These questions only grow more complex when considering the rise of Automated Case-handling Mobile Robots (ACRs). To understand the optimal solution or mix of solutions their organizations’ unique warehouse needs, the following considerations must be made: 

• Dynamic or static? — AS/RS systems are static and typically shuttle-based systems that store and move product to goods-to-person or goods-to-robot pick stations. Once installed, they cannot be easily moved, although when created in a modular fashion – something most AS/RS manufacturers now do – they can easily be expanded to add additional storage and throughput capacity. In contrast, AMRs operate in a dynamic environment, moving among workers and assisting in the sortation and transportation of goods. ACRs include aspects of both – functioning as AMRs but storing and moving products similar to an AS/RS, but using more traditional racks rather than lifts and shuttles, and achieving slower throughput than shuttle-based systems. 

• Sorting, moving, picking or all three? — If you are looking for a warehouse solution that simply moves product within the warehouse, then an AMR is the logical choice. AMRs can dramatically increase a warehouse’s output while addressing what is often the single most significant time sink: the 70% or more of the workday employees spend walking to access and move items.  

• High throughput or even higher throughput? — In operations where maximum throughput is required, a shuttle-based AS/RS is the gold standard, offering not only the speed but also the exceptional sequencing capabilities needed to move high levels of inventory out of storage in the right order. But such systems require scale – more on that below – to function at their full capacity. This of course is relative, as ACRs also achieve high throughput when compared to the manual processes they often augment or replace.  

• How varied are the SKUs you must process? — Today’s AS/RS are widely versatile – some systems handle cartons, trays and totes for greater versatility. However, AMRs can transport an even greater range of SKU than tote-based AS/RS, including heavier or larger items. Regardless of the SKU variety, sequencing needs must be considered as well. As previously noted, AS/RS offer exceptionally robust sequencing abilities.  

• More space around and overhead? — AMRs result in more traffic, which when combined with the humans they function alongside require more warehouse floor space. AS/RS in contrast require a much smaller footprint and offer the potential for far greater storage capacity, but need more overhead height to keep lifts working at all times to achieve maximum throughput capabilities. The taller a structure, the more effective an AS/RS can become, while ACRs – at least for now, are largely limited to racks that are 35 feet high or less.

• Greenfield or brownfield warehouse? — In addition to requiring greater height to maximize efficiency, AS/RS are highly advanced systems best deployed in purpose-built facilities that can take advantage of the smaller footprint they can operate within and feature stronger floors to handle the equipment. In contrast, many older or brownfield facilities do not offer the height and required floor strength, making it easier to deploy an AMR-based solution.

• Is an automated fulfillment system needed right now? — AS/RS systems should be designed to address each organization’s unique needs, whether it’s the need for exceptionally fast throughput and extensive storage density or robotic picking stations. To design, build and test such a system is a project measured in months, not days. In contrast, an ACR system can typically be created and deployed in much less time than a shuttle-based system. AMRs also do not need to be a long-term capital expenditure – a benefit for smaller warehouses that are just beginning their automation journey. This is driving the Robots-as-a-Service trend, in which organizations lease AMRs as needed – for example to augment a picking operation during the peak holiday season.

Just as important as the above considerations, materials handling leaders must remember that AMRs and AS/RS can complement one another. For example, an AMR can move items into reserve storage when overflow capacity is needed, deliver items to an AS/RS system, handle items that are too heavy or large for a shuttle, transport goods as needed from station to another in an AS/RS facility, or even sort goods for individual orders by picking from a pallet or tote. 

Every organization has unique needs, constraints and opportunities that will determine if an AS/RS system, AMR – or ACR – are best for them at any given time. Simultaneously, all warehouse automation should be considered in an integrated fashion, something that requires partners who have experience orchestrating the expanding array of automated solutions omnichannel retailers have to choose from.

Author Bio

Andy Lockhart is the director of strategic engagement, warehouse solutions, North America, where he provides Vanderlande’s retail customers – including many of the world’s best-known brands – with the innovative, scalable systems, intelligent software and reliable services needed to optimize distribution and fulfillment operations. Lockhart received his master’s in electrical and electronics engineering from King’s College London and his bachelor’s in electronic physics from Royal Holloway, University of London.