Introduction
With the increasingly expanding size of the warehouses, libraries and other storage facilities, and the rising number of items that need to be stored, organized, kept account of and retrieved on a regular basis, the question of optimizing storage space and speeding up the process of placing and retrieving items in the storage is very relevant. Nowadays this task is often delegated to the automated storage and retrieval system (ASRS), which can handle items of various sizes and weights: from heavy pallet loads in the large warehouses to a single book in a library.
Definition
Automated storage and retrieval system is the set of equipment and computer controls that are responsible for handling, storing and retrieving items from the storage ("AS/RS", n.d.). In case with the automated storage and retrieval systems, the items are stored in a predefined location in the storage, thus, making it possible for the computer-controlled system to locate and retrieve the needed ones. The ASRS systems may vary in the degree of automation ranging from fully automatic computer-controlled setups to manually controlled order-picking machines. Essentially the size of the storage and the quantity of items that need to be taken care of define the degree of automation for the ASRS: for large warehouses higher degree of automation makes more sense.
Types
There are two general types of the ASRS, which are defined by the way the items are stored and retrieved: Fixed Aisle ASRS and Carousel/Vertical Lift Module (VLM). Although they both operate under the same basic principles, different approach for storing and retrieving items is utilized in both cases and they have different advantages and disadvantages.
The Fixed Aisle ASRS consists of the storage shelves and ‘shuttles’, which travel horizontally between the shelves. These shuttles are able to travel in the vertical dimension as well in order to reach the upper shelves. There is a newer technology being implemented for the Fixed Aisle ASRS in which horizontal and vertical movements are delegated to different devices. In this case the vertically moving device handles the item’s location and retrieval, while the horizontally moving device is responsible for delivering the item to the collection point (Rogers, 2012). Carousel ASRSs can be divided into two categories: horizontal and vertical. They both operate in a similar way, the only difference being in how the items are stored. In case with the horizontal ASRS, the set of shelves, rotating around an oval construction is used. Vertical ASRS is similar, only in this case the shelves are rotating in the vertical dimension.
The Vertical Lift Module looks similar to the vertical ASRS, but the shelves are fixed and it is the VLM itself that is moving and retrieving the items from the shelves. The module’s movement is restricted in the Y axis only.
How it works
The ASRS system is computer-based and is able to retrieve items from the predefined locations in the storage. This means that the storage must have a consistent setup and all manual changes on the shelves should be properly recorded, so the software is aware of them. Depending on the storage, there can be different ways to request item retrieval. In case with a library it is an identifier, likely, a shelf number and book’s barcode or any other identifier used for it. In big warehouses, which store thousands of items, often grouped together, there may be an option to request a certain number of a specific item. After the item is requested, the software determines its location in the storage using the identifiers provided. Items retrieval is usually scheduled in batches in order to optimize time needed for it (for example, items can be processed depending on their location in the storage: first all the items requested from sector A, then from sector B, etc.). Then computer directs the ASRS, which moves to the item and retrieves it for further transportation. There may or may not be a conveyor or an automated delivery vehicle to carry the item to the needed location, so, for example, in case of a horizontal or vertical ARSR shelves could just rotate in order to present an operator with the correct shelf, where the item is located.
Application
ASRSs can be used in any storage where the high degree of automation and storage density is required. Generally it is large warehouses with thousands of items, big catalogues or libraries, etc. Due to the different degree of automation ARSRs offer, they could be made useful in virtually any storage space, saving floor space and decreasing labor costs.
Advantages and disadvantages
ASRSs are used in order to optimize storage space and to speed up the storage and retrieval of items. Since automation reduces human error, there is a smaller possibility of accidents and safety issues at the workplace. Another advantage of ASRS is decrease in labor costs, because there is no need to hire and manage a team of workers responsible for transporting and storing items; a few trained ASRS operators can cover the workload. It is possible to gather statistical data with the help of ASRS in order to assess which items are being requested frequently and optimize the storage in such a way, that all the most popular items are easily accessible. It can also help companies to analyze which products are in demand by tracking the quantities of retrieved items. Probably, a minor disadvantage of ASRS is that the warehouse has to be modified in order to house the system and it can be difficult and time-consuming to convert and existing storage into an ASRS-managed one because it requires a complete inventory check before all items can be accessed by the system.
References:
AS/RS. Mhi.org. Retrieved 14 April 2016, from http://www.mhi.org/as-rs
Rogers, L. (2012). Automated storage: Shuttle technology is taking off - Article from Modern Materials Handling. Mmh.com. Retrieved 14 April 2016, from http://www.mmh.com/article/automated_storage_shuttle_technology_is_taking_off
