Automated Storage & Retrieval System (AS/RS) Types & Uses
Automated Storage and Retrieval Systems (AS/RS) were once considered out of reach by many smaller order fulfillment operations and retail warehouses, who did not have the budget to invest in such advanced technology.
But as AS/RS technology has rapidly advanced over the years, new options provide a wide variety of size, speed, cost, and flexibility, and has caused the rate of system adoption skyrocket. This has made AS/RS technologies one of the most popular and impactful investment options available to most operations.
Are you still on the fence about the role that automated storage and retrieval might be able to play in making your operation more efficient and profitable?
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Below, we’ve gathered information that you can use to make a more informed decision about whether or not AS/RS is right for your operation, including the different types, applications, and cost factors related.
What is an Automated Storage & Retrieval System (AS/RS)?
An automated storage and retrieval system (AS/RS)—also called AS-RS or ASRS—is a type or genre of warehouse automation technology specifically designed to buffer, store, and retrieve product and inventory on demand.
AS/RS technology varies substantially, and can consist of shuttles, cranes, carousels, vertical lift modules (VLMs), micro-loads, mini-loads, unit-loads, or other systems. It is often integrated with a warehouse execution software (WES), warehouse management software (WMS), or other controls.
Benefits of AS/RS
By automating the low-value and easily repeated task of inventory storage and retrieval, AS/RS brings many powerful benefits to the operations that utilize it, including:
- More efficient use of floor space
- Ability to reclaim unused vertical space
- Increased inventory storage density
- Improved ergonomics and safety, resulting in fewer accidents
- Increased throughput
- Reduced labor costs
- Fewer labor constraints due to labor shortages
- Often modular design for maximum flexibility
- Increased order picking accuracy
- Improved product security for premium inventory
Uses & Applications of AS/RS
1. Goods-to-Person for Order Picking and Packing
Picking, packing, and processing orders is one of the most time-consuming tasks in the order fulfillment process. In fact, the process of walking and manually picking orders can account for more than 50 percent of the time associated with picking. AS/RS offers an alternative to this through the use of Goods-to-Person (GTP, or G2P) order picking.
In a goods-to-person order picking system, the worker does not physically move from product location to product location to pick an order. Instead, a mini-load AS/RS crane, shuttle, AMR, carousel or VLM is able to retrieve the necessary stock from storage and delivery it directly to the worker, who operates in a pick/pack station. Once the appropriate amount of product has been picked, the stock is returned to storage and the next item needed for the order is delivered to the worker for picking.
This can be done on a full-case or split-case basis, depending on the operation. In either scenario, the AS/RS can sequence product so that it makes the most logistical sense—allowing cases of heavy product to be placed on the bottom of a pallet, for example, or organizing product so that similar products are together or in sequence to match a store’s layout, shipping zone, and cut-off time, to name just a few options.
2. Staging Orders for Shipping
The impact of e-commerce and omni-channel delivery on the order fulfillment process can not be overstated. Customers are now able to shop and place orders around the clock, and they want their product delivered fast and on time. But even if an operation accepts and processes orders 24/7, there are often constraints to shipping windows: Due to worker shifts, for example, or exorbitant night and weekend delivery fees.
To make up for these constraints, an operation can pick and process orders continuously and use an AS/RS to place them in a buffer storage to stage them until the shipping window is open. This saves time and allows an operation to continuously produce, even when orders can not physically leave the facility.
3. Managing Buffer Storage
In a typical warehouse, different processes take different amounts of time to complete. If these discrepancies are not properly managed, then all it takes is a poorly-timed piece of equipment or zone slowdown in any stage to bring an entire operation to a standstill or mass slowdown.
Buffering aims to prevent such a breakdown by ensuring that enough supplies/product are always on hand in different stages to keep an operation running. But while buffering makes sense, poorly managed it can become a logistical nightmare, requiring miles of conveyor to properly buffer and stage.
AS/RS has the potential to replace these conveyor buffering systems, allowing an operation to efficiently store buffer product and retrieve it as necessary. Depending on the specifics of the operation, this buffer management can be put in place in multiple areas of an operation’s workflow, whether that is staging product/raw material as it is delivered (“Inbound Receiving Buffer”) or storing inventory exactly where it will be needed along the production line (“Assembly Line Point-of-Use Buffering”) or (Order Consolidation) holding multiple portions of an order picked in different zones and then consolidating them for final packing and shipping.
4. Storage and Point of Use Storage
One of the primary benefits of AS/RS is its ability to store product in a way that makes the most efficient use of available space, especially over the long term. By implementing AS/RS, an operation can automate their long-term storage of raw material or product and retrieve what they need, when they need it.
By integrating the AS/RS with their Warehouse Execution Software (WES) it is also possible to intelligently utilize and optimize inventory via FIFO (First in First Out), LIFO (Last In First Out), lot numbers, expiration dates, order cut off times, packaging requirements and many organization and industry specific requirements.
Types of Automated Storage & Retrieval Systems (AS/RS)
Automated storage and retrieval systems (AS/RS) come in two main varieties: Unit-Load AS/RS and Mini-Load AS/RS. Between these two main buckets, there are six primary types of AS/RS systems:
- Unit-Load AS/RS Cranes (Fixed-Aisle & Moveable Aisle)
- Mini-Load AS/RS Cranes
- Shuttle- and Bot-based AS/RS
- Carousel-based AS/RS (Vertical, Horizontal, and Robotic)
- Vertical Lift Module (VLM) AS/RS
- Micro-Load (Stocker)
We explore each of these in more detail below.
Unit-load AS/RS systems are typically used to handle exceptionally large and heavy loads ranging from 1,000 to 5,500 pounds. This capability allows for unit-load AS/RS to handle full or partial pallets and cases.
Usually, unit-load AS/RS consists of narrow aisle racks, which can extend to heights greater than 100 feet and which house pallets of product and inventory. These racks are paired with a crane, which is used to physically place and retrieve pallets as needed.
Unit-load AS/RS is a particularly helpful option when pallet-level storage is limited and quick retrieval is critical.
The two primary forms that unit-load AS/RS takes are fixed-aisle and moveable aisle cranes.
Fixed-Aisle Unit-Load AS/RS Crane
In fixed-aisle unit-load AS/RS systems, pallet racks are arranged with narrow aisles between them. A crane travels between these aisles moving both vertically and horizontally to retrieve and store product. The crane is fixed to a single aisle of pallets.
Moveable-Aisle Unit Load AS/RS Crane
Moveable-aisle unit load AS/RS works much the same way as fixed-aisle unit-load AS/RS. It consists of a crane moving between narrow aisles of pallets along some kind of track. The key difference is that it is not fixed to a specific aisle. This capability allows a single piece of equipment to service multiple aisles and, ultimately, a greater working space.
Mini-load AS/RS typically handles smaller loads (up to 75 pounds) compared to unit-load systems. Instead of full pallets, mini-load AS/RS handles totes, trays, and/or cartons. Sometimes, these systems are called “case-handling” or “tote-stacking” systems.
Mini-load AS/RS is especially well-suited for operations that require storage locations for a large amount of SKUs, but which lack the floor space required for traditional carton-flow shelving to provide a pick face for each SKU. Mini-load AS/RS systems can also be used to buffer and efficiently release/sequence product to picking or palletizing stations, and can be used to automatically replenish pick locations like carton-flow.
Shuttle-based AS/RS delivers inventory via a shuttle or “bot” that runs on a track between a racking structure.
They can operate on a single level or multiple levels, depending on the needs of the operation, and can be battery- or capacitor-powered. The shuttles deliver the tote or carton to a workstation integrated with the system.
When an item is requested, the shuttle drives to the location of the product and retrieves the tote or carton that contains the requested item. The shuttle will then take the tote/carton directly to a workstation or transfer it to a conveyor to convey the tote/carton to a workstation.
Different shuttle models utilize different designs to provide different benefits. For example, one model is vertically oriented to optimize floor space. The shuttles move on the perimeter of the rack and then move into an aisle to extract a tote and delivers it to its integrated workstation.
A third shuttle model utilizes vertical rack, but each bot moves on the floor and climbs vertically to extract its tote. Then it comes down to the floor and independently delivers the inventory to a remote workstation. It will queue at the workstation until picked and then is automatically assigned a new task and it repeats the process.
Carousel-based AS/RS systems consist of bins of product or inventory which rotate continuously along a track. When the operator requests a particular item, the system will automatically rotate so that the appropriate bin is accessible so that the item can be picked. An integrated lightree will indicate to the picker which carousel, shelf, and item to pick.
Carousel-based AS/RS may consist of either a horizontal carousel (bins move horizontally, as on a merry-go-round) or a vertical carousel (bins move vertically, as on a ferris wheel). Horizontal carousels are often utilized for small items and parts, as well as documents or raw materials.
Robotic horizontal carousel AS/RS is another variety which provides fully automated AS/RS functionality.
In these systems, up to three tiers of carousels are stacked on top of each other, and totes or cases are loaded on each shelf level. All three vertical carousels work independently to present the necessary inventory to an inserter/extractor device that runs horizontally in front of them. The inserter/extractor takes as many as two totes or cartons per trip to take-away conveyor, which delivers the goods to a workstation, and picks up returning inventory, placing it back in a waiting shelf. It is possible to increase capacity and throughput by increasing the number of carousel rows with an inserter/extractor in front of it.
Vertical Lift Module (VLM)
A vertical lift module (VLM) is an enclosed system consisting of an inserter/extractor in the center and a column of trays on either side. It is a form of goods-to-person technology.
When an item is requested, the inserter/extractor locates the necessary tray, retrieves it, and delivers it to an operator, who completes the order. Once the order is complete, the VLM will return the tray to its proper location before retrieving the next requested tray.
Trays may either be fixed or dynamic. In fixed systems, individual trays will always be returned to the same location; in a dynamic system, where individual trays are stored will vary.
A Micro-Load Stocker provides discrete or individual totes or carton storage and retrieval. It is ideal for buffering, sequencing, and point-of-use items in a high-density footprint.
The system is enclosed, and has an inserter/extractor device that runs in the center of the system, picking a specific queue of inventory and then discharging them onto awaiting conveyor or workstation. Different models store and retrieve differently, by taking either one item or a group of up to five items in one pass.
This system can also be used to store SKUs until needed, discharging them onto awaiting conveyor. It can be integrated with other AS/RS systems to improve the other systems’ performance and dramatically reduce conveyor and floor space requirements.
AS/RS Cost Factors
As is the case for virtually any warehouse automation technology, the final cost of an automated storage and retrieval system can vary widely from operation to operation and even from industry to industry. The surest way to get a clear picture of what it will cost to implement AS/RS in your operation is to request a consultation from a knowledgeable and trusted systems integrator.
That being said, by understanding the different factors that typically influence the final cost of investment, it is possible to estimate where on the cost spectrum your new system is going to fall. Here are the seven most important cost factors of AS/RS that you should consider:
- Available clear height in your facility
- The type of environment where it will be implemented (ambient, refrigerated, freezer, clean room, etc.)
- The size (cube) plus (and quality) of the load to be handled
- The weight of each piece
- The inbound and outbound systems in place to convey inventory to and from the system
- Whether the facility is steel-frame or rack-supported
- Current labor costs and quantity of labor
Is AS/RS right for your operation?
Whether or not AS/RS technology makes sense as a part of your operation will depend largely on the specifics of your individual business. Factors like your business cycle, operational goals, level of growth, and available investment capital will all impact your ability to implement a system, and it would be a good idea to speak with warehouse design consultant or systems integrator to help determine if AS/RS makes sense for you.
If you answer “Yes” to any of the questions below, then implementing automated storage and retrieval could be a smart move for your operation:
- Do you need increased throughput from your operations?
- Are your labor costs increasing?
- Are you having difficulty hiring for open positions?
- Is retention of qualified workers a challenge?
- Are you running out of space within your facility?
- Do you need better inventory control?
- Do you have worker ergonomic concerns or issues?
Romaine has spent over 30 years involved with organizations looking to optimize their distribution, manufacturing, and warehousing operations. Focusing on the customer’s processes, automation and business model, Romaine has helped dozens of organizations improve profitability by reducing labor, floor space, errors and inventory while improving accuracy, inventory turns and cut-off times.
Within the industry trade association, MHI, Romaine has taken numerous leadership positions including: Chairman of the Automated Storage & Retrieval (AS/RS) Group, Chairman of the Order Fulfillment Council of America, Chairman of the Warehouse Execution Systems Group and was one of the originators of the Carousel and VLM Product Section Group. He has also spearheaded the efforts to create the first ANSI industry safety standards for horizontal carousels.
Romaine is a frequent editorial and information contributor to hundreds of publications, blogs and online publications and has been a speaker at dozens of Supply Chain, Logistics, Lean and Facility organizations and functions. Just a few include the Parcel Forum, Institute of Industrial Engineers (IIE), Promat, North American Material Handling, Modex, National Mfg Week, Southern California Plant Operations, NJ Material Handling Assoc., Applied Ergonomics, Warehousing Education & Research Council (WERC), Lean Manufacturing Conference, Council of Supply Chain Management Professionals (CSCMP), NeoCon, Health Information Distribution Association (HIDA), National Catalog & Operations (NCOF), CSCMP and more.
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