Among the automated equipment options, goods-to-person (GtP) automated storage and retrieval systems (AS/RS) hold, organize, track, and access a large, highly variable volume of vastly different SKU profiles in an extremely dense footprint. They retrieve and deliver items required for orders directly to human (or robotic) pickers positioned at workstations — tremendously boosting the productivity of associates who previously spent as much as 70% of their shift traveling through the warehouse aisles to fill orders.
There are a variety of AS/RS types, designs, and configurations. Among the most flexible are systems that deploy powered shuttles which travel independently throughout a grid of multiple, closely spaced levels. Storage locations within the structure hold totes, trays, or cases of product. Each shuttle is outfitted with an inserter/extractor device that automatically stores or retrieves items as directed by the AS/RS’ integrated control software and the facility’s overarching warehouse management system (WMS) or warehouse execution system (WES) software.
To ensure a successful shuttle based AS/RS deployment, however, it is crucial to choose the most appropriate type for a given operation.
A Comparison of Shuttle Technologies
There are several shuttle types available in the AS/RS marketplace. The key difference is among their directional movement capabilities — including travel forward and backward, side to side, and up and down within the structure — as they store and retrieve inventory.
One-Dimensional Shuttles travel forward and backward within one aisle and level. These limitations make the system less adaptable to changing order profiles or volumes, and therefore ideal for operations with limited stock keeping units (SKUs) and consistent order profiles.
Two-Dimensional Shuttles have two sets of wheels for travel forward and backward as well as side to side. The addition of a lift to the storage structure allows shuttles to be transported to levels with higher pick volumes as needed. These systems are ideal for GtP picking, lower throughput requirements, or handling of medium- to low-velocity SKUs.
Three-Dimensional Shuttles self-propel in all three planes — forward and backward, side to side, and up and down — delivering payloads directly to a picking workstation, no lifts required. Although this increases shuttle availability, it can also inhibit overall system capacity and performance if shuttles get held up waiting their turn to travel to the pick stations. These systems are therefore ideal for lower throughput operations, including GtP picking and handling of medium- to low-velocity SKUs.
Roaming Shuttles combine two-dimensional shuttles for placement and retrieval of required items with integrated product lifts and buffering conveyors. When an item is needed, the shuttle closest to the storage location travels to that position, removes the full tote, tray, or case, and travels to a lift platform designated for picks. It deposits its payload for movement to a picking station via conveyor. Separate lifts pick up totes sequenced for return to storage.
Tote delivery to the inbound and outbound lifts is sequenced and buffered, allowing all totes with items required for an order to be routed together to a designated picking workstation. This enables roaming shuttle AS/RS to deliver high throughput at rates up to 600-plus totes delivered to a single workstation per hour. They are ideal for high volume picking operations, such as e-commerce order fulfillment. They also deliver:
- Improved order accuracy
- Increased flexibility in day-to-day operations
- Resolved labor challenges
- Shortened order lead/cut-off times
- Reduced downtime and higher availability
Meet the FASTPICK Roaming Shuttle AS/RS
A recently released Vanderlande white paper, “How Roaming Shuttles Improve Order Fulfillment Operations,” explores how implementing goods-to-person roaming shuttle AS/RS technology improves the customer experience, optimizes operations, and maximizes profitability. It also details how FASTPICK — a new solution that leverages roaming shuttles and automatically sorts and sequences picks one order at a time — provides an optimal solution to retail order fulfillment challenges.