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How do automated storage and retrieval systems (ASRS) work? [Definition, Types, Pros and Cons]

Written on
February 4, 2021
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How do ASRS work?

Automated storage and retrieval systems comprise a variation of computer-controlled systems that automatically place and retrieve loads from set storage locations in a warehouse with accuracy, precision and speed.

Definition Automated storage and Retrieval System (ASRS)

So what is the definition of ASRS? An automated storage and retrieval system is a type of warehouse automation technology that handles, stores, and retrieves materials on demand. This technology varies and can include many elements such as shuttles, cranes, vertical lift modules (VLMs), carousels, unit-loads, mini-loads, and robots. AS/RS are designed to automate operations such as sorting, unloading, staging, putting away, storage, order-picking, and loading.

ASRS Types

The following are the various ASRS Types.

Unit-Load AS/RS

These are machines that can store large loads, typically over 1000 pounds. It usually operates on pallets with a storage rack structure above 100 feet.

Mini-Load AS/RS

These technologies operate the same unit as a unit-load AS/RS as a mini-A/RS but handle lighter loads typically weighing less than 1000 pounds. They consist of crane-mounted load handling equipment and travel either on wheels or rails. They deliver fast acceleration speeds at one load per minute with throughput rates of 60 to 100 lines per hour.

Vertical Buffer Modules (VBMs)

VBMs are bin handling systems that are engineered for smaller applications. They include an enclosed shelving system with a movable mast running down an aisle at the centre to pick store and store totes. For maximum throughput, the system works ahead of the operator and queue up the next pick. An inbound and outbound conveyor automatically delivers totes, or they can be picked from a turntable station.

A manual station can be configured to replenish the totes during picking, which means that picking can continue uninterrupted by replenishing activities. The conveyor can connect to multiple units to deliver units to remote picking stations. VBMs are designed to be scalable, modular, and highly energy efficient.


These are used for the automated handling of trays, totes, cartons, or all three at the same time, either manufacturing or warehousing. Robotic shuttle travels independently from one level to the next on narrow rails at the storage levels. They handle totes weighing from 35 to 65 pounds with throughput rates of 200 to 700 lines per hour. The number of robotic shuttles on the system determines the throughput rate.

Floor Robots

Floor robots store loads on portable storage shelves that can be retrieved and moved by a set of autonomous mobile robots. The operator can then access the inventory and select the required items. The mobile robots then return the shelf for storage. They have a throughput rate of 100 to 300 lines per hour, ideal for slow to medium velocity inventory. The addition of more robots can increase the throughput rate. Each shelving system had a standard weight capacity of 100 pounds, which can be improved with the heavy-duty model up to 3000 pounds.

Vertical lift modules (VLMs)

They are one of the most flexible technology and are designed to automatically adjust when your inventory changes. These enclosed dynamic storage solutions have trays capable of handling up to 2,200 pounds and consist of trays with an inserter/extractor in the centre. The automated inserter/extractor locates and retrieves stored trays at slow-to medium velocity from both columns to deliver them at a high-waist pick window to the operator at rates from 125 to 475 items per hour.

Automatic tray extractors and an overhead crane can be placed on systems that store the heaviest items to help the operators handle and maneuver their picks. The VLM stores items dynamically to maximize storage density since the height of the items in the storage tray is measured. This helps to save up floor space.


  • Multiple Openings
  • Save time and space
  • Maximizes vertical space in a minimum floor layout space.
  • Easy and paperless order handling to optimize warehouse logistics

Horizontal Carousels

They are made of dense bins that rotate horizontally on an oval track. Horizontal Carousels can handle cases and items that weigh up to 200 pounds. They are usually installed in groups known as pods to generate maximum picking speed. This offers access to products from one carousel while other items are in the queue. This ensures high throughput rates and the simultaneous fulfillment of multiple orders. They deliver high storage density and great space utilization. For an enclosed system, an automated door system can be installed.


  • Reduces walking and waiting times
  • Achieves maximum storage density and save up on floor space
  • Increases storage capacity through optimal use of available room depth and low ceiling headroom

Vertical Carousels

They have been around for decades and include a series of carriers attached to a chain drive. There is a motor that powers the carriers in a vertical loop around a track. Vertical carousels deliver slow-to medium velocity items quickly and safely to a work counter positioned ergonomically by an operator. New bells and whistles can be added with each revision, but the mechanism is still the same.

Typical throughput rates range from 100-400 lines per hour. Light-directed picking technologies and batching stations that offer simultaneous picking of orders can boost the rates. Each carrier has a capacity of 1,650 pounds, making it a cost-effective and reliable solution.


  • Less searching for items with 100% accuracy
  • Saves up floor space
  • Optional totes, bins, or multi-level carriers for small and large components increase  storage flexibility

Single, Double and Multi Towers

They are designed to handle and store heavy loads, especially materials made of metal or profile rods and tubes. They are commonly used in the production of intermediate storage of material, inter-operative warehouse, or near bending or cutting machines.

Single, Double and Multi Towers

Single plate towers consist of welded structures, designed according to usual shipping formats and weights of metal sheets. They have an optional ground plan and height made from a firmly welded structure adapted for vertical storage of single loading units.


  • Quick and full access to stored goods
  • Payload up to 5 tons per carrier
  • Designed and adapted for heavy goods

The Cons of AS/RS

High Initial Investment

The cost of purchasing these systems is expensive in the short term, even though they are likely to reduce labor costs and increase productivity in the long run. Smaller operations may not have access to capital to acquire the systems, although they may explore leasing options.


This equipment will inevitably require regular maintenance and occasional repair. This may result in operational downtime. The cost of maintenance is a major factor to be considered, although it may be lower than the cost of hiring manual labor.

Not Suitable for Highly-Variable Operations

Automated storage systems are ideal for operation with regular, predictable, and repetitive tasks. Variable operations may not work well with the system. Process and analysis can also be difficult to facilitate since they work on present systems.

Can Require Technical Skill and Retraining

You may need to retrain employees or employees have moved to another position within the company or have left, to handle and operate the systems, this may lead to downtime, if a proactive approach has not been considered.

Common AS/RS Systems Applications

These systems manage small parts inventories, work-in-process, sub-assembly, maintenance, and repair parts, usually in the manufacturing and distribution sectors. The following are some of the common applications.

  • Order picking. Offers fast, compact, and reliable access to loads for distribution
  • Storage. It offers high-density storage for components and parts used in the manufacturing process
  • Buffering. Providing a high dense storage solution for the process of buffering
  • Kitting. It manages how inventory is received, sorts the components, and stores kits
  • Assembly-store sub-assemblies or work-in-process for later use
  • Order consolidation. The system offers a compact solution to hold incomplete order temporarily before shipment
  • Replenishment and returns. The system manages inventory for returns and replenishment processes
  • Maintenance and repair parts. It offers compact storage of maintenance parts onsite to reduce downtime
  • Climate controlled and clean room environments. It offers clean, cold, and dry management of storage
  • The tool, die, and molds. The system secures and ergonomic handling of heavy and expensive tooling

Signs You Need AS/RS Systems

Industries that benefit from AS/RS include E-commerce, machinery, hospital logistics, electronics, automotive dealership, government, medical device manufacturing, warehousing, and distribution.

  • Excessive search time. You should consider automation If workers spend a lot of time visually searching for correct items and matching up part numbers at a picking destination
  • Replenishment overload- you may need AS/RS if your workers take up the same amount of time to replenish and picking
  • Picking Errors. If you notice you have many picking errors, you may consider automation to avoid wasting money and risking the company reputation
  • Extensive travel time. If workers are consuming a lot of time traveling in a shift to access inventory, then you may need automation to save time
  • Slow throughput. If the company struggles to meet the order cut-off time or requires seasonal employees to keep with demand, you should consider the AS systems.
  • Misplaced inventory. You may consider automation if your inventory gets temporarily lost or misplaced or unexplainably missing frequently
  • Damaged items. You may need AR/RS if your inventory is often damaged or unusable
  • Safety. You may consider automation if your operators are a risk of injury
  • Out of space- if your facility id at maximum capacity and there is no room for growth

Benefits of ASRS

Improved Floor Space Utilization

One of the biggest benefits of AS/RS is better floor space utilization. They help to remove isle space shelving and utilize the full ceiling height of the facility. These systems provide high dense storage in a compact footprint. They utilize tightly configures holders to effectively organize the inventory to increase storage capacity. The inventory is tightly compressed by the integrated inventory management software, which manages the cube space. The recovered floor space can be utilized in various ways to add value.

Reduced Labor Requirements and Costs

AS/RS significantly reduces workers walk and search time by delivering the required items to the operator. Walking around during shifts amounts to time wasted, which is worsened by the time they have to spend to visually search the shelves. This takes a lot of time since they also have to match up the part numbers to the correct item.

Pick time is also maximized since the automated solution interfaces with both inventory management and order management software. This ensures that all items can be picked in one cycle or rotation of the machine’s trays. AS/RS solutions can compensate for unreliable or scarce labour.

Reduced Picking Errors

Automated storage solutions help to reduce human error and improve pick accuracy. They are integrated with a variety of light-directed picking technologies and message centres that send information to the operator for more accuracy. These systems pinpoint the carrier's exact area where items will be picked and show the part number or description and the required quantity.

Increased Pick Throughput

Automated storage technologies use the goods to person concept to reduce walk and search time to improve throughput. In typical manual operation, pickers have rates of about 50 lines per hour. Light systems can be integrated to direct the operators to the precise location of the pick to increase the throughput rates. There is also another way throughput rates can be increased and involve integration with inventory management software. Orders with a common item are grouped together and then delivered to a nearby workstation for sorting.

Tighter Inventory Control

Inventory is housed in a fully closed system where it remains safe and secure through controlled inventory management. Automated storage systems can be configured to restrict access to unauthorized personnel through a personal login and password. If any goods are missing, they can be tracked to a specific individual. The security measures and enhanced level of accountability minimize the chances of inventory shrink and its negative impacts.

AS/RS solution also keep items clean and protected from exposure to dust, dirt and other environmental contaminants. This extends their useful life and reduces damage to components or products. A facility warehouse management system and enterprise resource planning system can be interfaced with machines to allow you to track stock levels to avoid physical counts and reduce the amount of inventory on hand. LIFO (last in, first out) and FIFO (first-in, first-out) picking systems can also be used for better inventory runs.

Improved Ergonomics

AS/RS systems deliver items to operators at an optimal ergonomic height. This is usually between a person’s shoulder and knees or the golden zone. Thus, eliminating the need to bend down or stretch up to reach items. Other systems have a lift table that presents trays, bins, or shelves at an easy reach. This also reduces the risk of workplace injuries, insurance premiums, absenteeism, and claims of worker’s compensation.

Contact Us for More Information

To learn more about Automated Storage and Retrieval Systems, simply contact us at +1 (844) 909-0437 today. You may also email the company at or via this form.

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