Many high-throughput retail-distribution centers face a growing logistics challenge: how to prepare small quantities of diverse parts to ship and arrive on schedule with near-zero errors while coping with a growing variety of stock numbers and complex orders. To address this situation, new automated-storage and retrieval systems (ASRS) try to balance inventory complexity and throughput by offering part storage, automated selection, and shipping that costs less and uses less labor.
Conventional ASRS have been storing and retrieving cases containing identical parts for some time. They have recently been expanded to handle small-quantity orders of several different items. However, several factors limit the efficiency of these systems. First, they often experience single-point failures that halt the entire store-and-pick operation. Second, they cannot easily be expanded to match the growth in shipments. This is particularly true regarding the ability to independently scale throughput and inventory during installation and over the life of the system. Third, the need to store and retrieve orders sequentially instead of simultaneously limits speed and efficiency in handling orders on a high-throughput basis.
New designs for piece picking have overcome these deficiencies, boosting order-processing speed without sacrificing accuracy. In addition to high throughput and cost-efficient distribution, this new machinery also supplies a higher density of storage and more modular flexibility, which promotes enlarging the system as needed.
This new approach is typified by the AutoStore system from Jakob Hatteland Logistics AS in Norway. AutoStore uses independently operating robots that move bins from a grid layout to individual pick stations. The distribution center’s immediate needs dictate the number of bins installed. But system flexibility accommodates future growth by making it easy to add more bins for more storage.
Each robot travels on two sets of wheels that let it move along perpendicular axes. Thus, all robots can reach any position and any bin on the grid, independently of other robots. And if one of the robots needs maintenance, for example, its tasks are automatically taken over by other robots.
The system accommodates almost any number of robots, and the number of robots determines overall throughput. Each robot has a lift for picking up, carrying, and placing bins stored in the grid. The robots wirelessly communicate with a warehouse-management system (WMS), and pick stations through a standard application interface.
Robots deliver each bin to a pick station where workers pick, place, or check inventory. The robot then returns the bin to storage. New bins are thereby delivered back-to-back so that operators rarely wait for one.
AutoStore holds approximately 30 min of live picking tasks in its queue at any one time. Should the need arise, any order can be redirected to any pick station to improve throughput. Control panels at each pick station display status information for the current order.
Using a modular approach lets storage bins, robots, and pick stations be expanded or extended. Size and form are no restrictions, as the system can adapt to different building heights, levels, and even surround obstacles such as pillars or walls.
The system places goods in the grid so that frequently used products are towards the tops of the stacks. Seldom-used bins sink to the bottom. This leads to shorter access times by reducing the distance between commonly used parts.
As each bin stacks on top of the other, the system produces up to 60% better use of space than other ASRS, and 300% better than conventional rack systems. Typical installations may see up to 87% of the available cube space used for storage.