How Automated Shelving Systems Work

Automated Shelving Systems

Storage space is a valuable commodity in warehouse facilities. Traditionally, warehouses use conventional shelving and racking systems for storing inventory items. In the warehousing industry, the storage method you employ can play a significant role in your ability to remain competitive. Depending on your operational goals and storage assignment policies, this may require automation.

Conventional Systems

In modern warehouses, conventional shelving systems and racks are the default storage solutions. They’re configurable, inexpensive, and simple to install. However, they are also more vulnerable to mechanical failure and safety challenges. Conventional systems fit into two broad categories:

Industrial Shelving

Industrial or solid shelving is designed to store relatively lightweight and loose items for retrieval by order pickers on foot.


The rack frame consists of upright columns connected by horizontal beams in a conventional racking system. A worker uses a forklift truck to load and retrieve pallets in these systems.

Automated Storage & Retrieval Systems

Automated storage and retrieval systems (AS/RS) allow modern distribution centers and warehouses to optimize their storage capacity and picking efficiency. Automated systems are available in various configurations to accommodate your warehouse’s floor plan and layout.

You’ll need to evaluate your storage and retrieval needs to determine whether an automated system is worth the initial investment. Some of the benefits of automation include:

Increased worker safety

Conventional racking and shelving systems can fail due to impact damage or overloading. This can cause a domino-like effect in which one rack topples another, causing catastrophic damage. Most automated systems are enclosed, protecting inventory and workers alike.

Increased productivity

Automated systems have the potential to significantly improve workflow and throughput efficiency. Using ID information (part number, bin number), the system can locate the item and signal its location to a worker.

One of the factors to consider is the retrieval-travel time of the system. This determines how quickly the system can store, locate, and retrieve items, delivering them to the picking station.

Reduced error rates

Automation can significantly reduce the picking error rate by electronically tracking inventory and delivering the products requested. It also guides workers to pick the correct items using various methods, such as pick-to-light systems.

Efficient use of space

Rack and shelf space are limited in modern warehouses. Vertical lift modules and carousels use vertical space more efficiently than competing non-automated systems.

These high-density systems allow you to re-allocate floor space for other purposes, such as building a larger docking station. It’s also a great way of reducing clutter and keeping valuable merchandise off the floor.

Types of Automated Systems

Automated systems for warehouses are available in a variety of designs and configurations, depending on the specific requirements of your business.

Horizontal Carousel Systems

Carousel Systems

Automated carousel storage and retrieval systems can be divided into two basic categories: horizontal and vertical.

Horizontal carousels: A horizontal carousel is one of the most efficient storage and retrieval methods in warehouses with a surplus of floor space but relatively low ceilings. The clear height is one of the most critical factors for determining the best AS/RS option. This is the vertical distance between the floor and the lowest hanging fixture, such as ceiling sprinklers.

You load inventory items into shelves or bins that travel along a motorized oval track in a horizontal carousel. When you need to access the inventory items, the bins stop at a designated access point.

Horizontal carousels save floor space, reduce pick error rates, and provide more security than open shelving systems. However, horizontal carousels also tend to be limited in the size and weight of the items they can store and deliver.

Vertical carousels: A vertical carousel uses a series of carriers attached to a drive chain that revolves like a Ferris wheel. The primary advantage of a vertical carousel compared with a horizontal system is that it has a reduced footprint and uses overhead space.

One of the downsides of the vertical carousel system is that it requires uniform weight and size distribution for stability. It’s also limited in its height and storage capacity.

Vertical lift modules

An alternative to carousel systems is the vertical lift module (VLM). Unlike vertical carousels, VLMs provide a more flexible storage solution; there are height limitations regarding the system and inventory items. A VLM can also substitute for heavy-load shelving.

A VLM stores inventory items in trays located in two enclosed vertical columns. In the center is an inserter/extractor that loads trays into the system and retrieves them in response to picking requests.

VLMs use a height sensor to determine the optimal storage position for the tray in the column. The VLM lifting mechanism places the tray in a designated retrieval bay at an ergonomically optimal height for a worker to find the items they need.

VLMs increase average retrieval time compared with conventional shelving and racking systems, increasing throughput efficiency.

An example of a vertical lift module is the Modula SLIM, a flexible vertical storage solution for the warehouse manager interested in expanding. Ranging in height from 7’10” to almost 23’, this system is available in several heights to suit your facility. At 23’, the SLIM has a 55,115 lb. payload, yet its footprint is compact, as reflected by its name.

FF-Flow-Rack AS/RS

A free-fall flow-rack AS/RS is a unique system for storing and retrieving products. The FF-Flow-Rack AS/RS design includes a deep rack consisting of several sloping bins and a gravity-driven conveyor with rolling wheels. This system allows products to slide, using gravity, from one side (storage) to another (retrieval).

Each bin has multiple locations to contain several identical products. On the storage face is a pick-up station, and there’s a drop-off station on the retrieval face. The operator manually removes products from the pick-up station for placement in the appropriate bin.

When product retrieval is required, the system ejects the product, which falls freely on a conveyor for transportation to the drop-off station.

Multi-aisle AS/RS

A multi-aisle AS/RS consists of non-moving storage racks separated by service aisles. A storage and retrieval machine moves horizontally and vertically along these service aisles to store and retrieve items from the various rack bays.

Mini-load AS/RS

A mini-load AS/RS consists of a crane or storage-retrieval machine that loads and retrieves lightweight carriers, like totes, trays, or bins. A mini-load AS/RS usually operates in conjunction with a racking system specifically engineered for use with automated systems.

Unit-load AS/RS

In contrast to mini-load AS/RS solutions, a unit-load AS/RS is designed to retrieve comparatively heavy loads (e.g., pallets). If you need a crane or SRM for storing and retrieving palletized merchandise, a unit-load AS/RS is the optimal solution.

Pallet shuttles

A pallet shuttle is a semi-automated storage system that uses electrically operated shuttle carts, each moving a single pallet load inside a storage rack. The pallet shuttle system is suitable for FIFO or LIFO inventory methods.

Mobile racking

A mobile racking system, also known as a movable racking system or mobile-rack AS/RS, allows operators to open aisles when loading and retrieval are necessary. When idle, the aisles can be closed, increasing storage density. An operator controls the mobile racking system remotely from a central control cabinet or on the floor using rack-mounted controls.

Like mobile shelving units, mobile racks employ various warning and detection systems to protect personnel and goods when closing one aisle and opening another. Mobile racking may be a cost-effective solution for your warehouse or distribution center if you need a flexible storage system.

Automated Cold Storage

Cold storage is necessary for safely storing and preserving perishable and temperature-sensitive goods, especially food products, plants and flowers, and pharmaceuticals.

Failure to store food products in a suitable temperature-controlled environment can contribute to the presence of food-borne illness; therefore, automating the process, including by implementing an inventory management system, is advisable.

Mobile Shelving

Mobile shelving systems maximize storage density by opening and closing aisles when needed for access. While mobile shelving systems may use manually operated hand-crank mechanisms, many are semi-automated. They use electronic systems to manage space and sensors to detect objects that may interfere with closing.

Fire Protection

Rack sprinklers are necessary for fire protection in high-density warehouse facilities; however, the use of automated systems may require custom solutions. When you’re considering installing automatic sprinklers in your warehouse, you’ll need to account for certain factors specific to your stored commodities.

These include storing housing materials, including wood products, and items containing expanded and unexpanded plastic materials. The use of wood pallets is also a potential fire hazard, contributing to the need for adequate fire-suppression systems.

Upgrade Your Warehouse with Shelving + Rack Systems, Inc.

At Shelving + Rack Systems, Inc., we can provide various storage solutions for maximizing the density and efficiency of your warehouse or distribution center. While conventional rack and shelf storage systems are sufficient for many businesses, automation has many benefits, such as increasing workflow and safety.

Contact us for more information so that we can help you select the optimal storage array for your company’s requirements.