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, which 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 sizes, speed, cost, and flexibility, and have caused the rate of system adoption to skyrocket by various distribution centers. 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 fully 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 a Fully Automated Storage & Retrieval System (AS/RS)?
A fully Automated Storage and Retrieval System (AS/RS)—also called AS-RS, 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, crane and aisles, Autonomous Mobile Robots (AMRs), horizontal and vertical carousels, Vertical Lift Modules (VLMs), Micro-Loads, Mini-Loads, Unit-Loads, stockers, or other systems. It is often integrated with a Warehouse Execution Systems software (WES), Warehouse Management Systems software (WMS), Warehouse Control Systems software (WCS) or other software and controls.
Benefits of AS/RS
By automating the low-value and easily repeated task of inventory storage and retrieval, AS/RS brings a wide range of 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 and injuries
- Increased throughput
- Reduced labor and its associated costs
- Fewer labor constraints due to labor shortages
- Often modular design for maximum flexibility
- Increased order picking accuracy
- Improved visibility and product security
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 operator’s 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, AMR (Autonomous Mobile Robot), mini-load AS/RS crane, shuttle, AMR, carousel or VLM— are able to retrieve the necessary stock and deliver it directly to the worker, who operates in a pick/pack station. Once the appropriate quantity 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 pallet, full-case or split-case basis, depending on the operation. In every scenario, the AS/RS can sequence product so that it makes the most logistical sense—for batch picking, 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 eCommerce 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 expedited delivery fees and order cut-off times
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, ensures improved accuracy, 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 inventory/products 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 recirculating conveyor to properly buffer and stage.
AS/RS has the potential to replace or mitigate these conveyor buffering systems, allowing an operation to efficiently store buffer products and retrieve them 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 products in a way that optimizes the use of available storage space, especially vertical cube. By implementing AS/RS, an operation can automate their long-term storage of raw material or inventory and retrieve what they need, when they need it (goods-to-person)—ensuring the most efficient use of warehouse space and labor.
By integrating the AS/RS with their Warehouse Execution Systems(WES) software 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 & Styles of Fully Automated Storage & Retrieval Systems (AS/RS)
Automated storage and retrieval systems (AS/RS) come in three main varieties: Unit-Load AS/RS (primarily pallets), Mid-Load AS/RS (inventory requiring custom handling requirements), and Mini-Load AS/RS (each or split case picking). Between these three main buckets, there are eight primary styles of AS/RS systems:
- Unit-Load AS/RS Cranes (Fixed-Aisle & Moveable Aisle)
- Mini-Load AS/RS Cranes (Fixed-Aisle)
- Shuttle AS/RS
- Carousel-based AS/RS (Vertical, Horizontal, and Robotic)
- Vertical Lift Module (VLM) AS/RS
- Micro-Load (Stocker)
- Vertical Sequence Systems (VSM) AS/RS
We explore each of these in more detail below.
Unit-load AS/RS systems are typically used to handle 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 take 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, and 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 products 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 in the system.
When an item is requested, the shuttle moves 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 deliver it to an integrated workstation.
A third shuttle model utilizes a 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.
Pallet Shuttle AS/RS pallets are automatically stored and retrieved within a multi-tier rack structure. The pallet shuttle is available in three primary types or models: 1 dimension pallet shuttle, two dimension pallet shuttle, and a three dimension pallet shuttle. Each system provides high density pallet automated storage and retrieval in ambient, cold and frozen environments. Each system utilizes a range of shuttle carts, AMRs (autonomous mobile robots), AGVs, forklifts and elevators and lifts. How do you know which pallet shuttle is best for you? Simply by calculating and reviewing your pallet size and weights, throughput requirements, peak activities, facility layout, forklift traffic issues, budget and growth projections. Each level of pallet shuttles (1D, 2D or 3D) do a great job, its a matter of evaluating the criterial and selecting the model best for your requirements.
Autonomous Mobile Robot AMR-Based High-Density Exotec AS/RS
An AMR (autonomous mobile robot) based high-density fully automated storage and retrieval system is designed in a way that uses three-axis AMR robots to travel vertically up a storage rack to retrieve the required inventory tote or case. The AMR stores the inventory or tote on itself, and then navigates down the rack and on the floor to any one of the remote order picking workstations. The AMR rides up the workstation’s ramp, and the integrated pick-to-light and software system indicates which item and how many to pick. The operator then places the appropriate item and quantity into one of the batched orders and the AMR leaves for its next assignment.
This system provides a tremendous amount of flexibility in storage density, throughput and labor requirements. Additional rack and AMR bots can be added, subtracted or moved to meet current and anticipated activity levels.
Go-Fer Bot AMR Autonomous Mobile Robots AS/RS
The Go-Fer Bot AMR AS/RS robot that moves on the floor and navigates under a rack of shelving, lifts the rack slightly, and moves it to a pickstation. The racks can be configured with totes, boxes, pallets, hanging garments, and loose fill, all within the same system to meet your needs. Likewise, integrated pick-to-light systems can be utilized to improve accuracy and throughput. This system provides high density storage, throughput and a very high ROI (Return on Investment). The system is also very agile allowing users to grow, shrink, modify and even move the system quickly and affordably.
Stacker-Bot Case Shuttle AMR ASRS
This AMR AS/RS robot extracts totes or cases from a shelving rack, places it on one of its storage shelves, then delivers the totes or cases to an awaiting conveyor, AMR, extractor system or workstation. The Stacker-Bot can interleave storing and retrieving activities in one path. Ideal for agile, high density and cost effective Goods-to-Person AS/RS system.
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 storage and retrieval 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 the 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) AS/RS
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.
Micro-Load Stocker Automated Storage and Retrieval
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 conveyors. It can be integrated with other AS/RS systems to improve the other systems’ performance and dramatically reduce conveyor and floor space requirements.
VSM – Vertical Sequence Module for Buffering and Sequencing
A Vertical Sequence Module provides high-density buffering for discrete tote sequencing applications. It is ideal for buffering, sequencing, and point-of-use items in a high-density footprint. The VSM totes can be stored and retrieved via conveyor, AMRs, AS/RS systems or manual pick window. The system stores totes on shelves within the unit(s). When a sequence of totes are required, the system pulls the totes from its storage and extracts them in the exact order or sequence as required.
AS/RS Cost Factors
As is the case for virtually any warehouse automation technology, the final cost of a fully automated storage and retrieval system can vary widely from operation to operation and even from industry to industry. The best way to understand which system is best for you and what it will cost to implement a Goods-to-Person 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:
- System throughput requirements
- Available clear height and floor space in your facility
- The type of environment where it will be implemented (ambient, refrigerated, freezer, clean room, etc.)
- The size and physical characteristics of the inventory 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 required (and saved) using an AS/RS system
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 operations. 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 a fully automated storage and retrieval system 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 and storage capacity?
- Do you have worker ergonomic concerns or issues?