Last updated: 15 November 2026
What an AS/RS is
An automated storage and retrieval system (AS/RS) consists of racking, machines that move loads in and out of the rack, and software that decides where each load is stored. Stacker cranes, shuttles and lifts replace forklifts and manual picking from shelves.
Companies invest in an AS/RS to use building height and floor area better, to reduce the dependence on manual labor, to raise stock accuracy and to keep throughput stable across shifts. It is also common in cold stores, where working conditions make manual operation difficult.
Main AS/RS types
- Pallet AS/RS (unit-load): stacker cranes run in narrow aisles and store pallets in high-bay racking, single or multi-deep. It suits large pallet stocks and tall buildings.
- Miniload: a lighter crane stores totes, cartons or trays. It feeds picking stations with a steady flow of small load units.
- Shuttle system: shuttles travel on each rack level and hand loads over to lifts. Because many shuttles work at the same time, shuttle systems reach high throughput and can be extended by adding shuttles and lifts.
- Pallet shuttle: a shuttle carries pallets into deep channels. It gives very dense storage for a limited number of products per channel.
Vertical lift modules, carousels and robot-based grid storage are related technologies for small parts. They follow the same principle of bringing the goods to the operator.
Pallet AS/RS, miniload and shuttle compared
| System | Load unit | Strength | Typical use |
|---|---|---|---|
| Pallet AS/RS | Pallets | High storage density and height | Production and distribution warehouses with large pallet stocks, cold stores |
| Miniload | Totes, cartons, trays | Reliable supply to picking stations | Small-parts storage, order picking, production supply |
| Shuttle system | Totes, cartons, trays | High throughput, scalable | E-commerce and retail fulfilment, order buffering and sequencing |
| Pallet shuttle | Pallets | Very dense storage | Few products in large quantities, buffer and shipping stores |
How to choose an AS/RS
The decision is based on the operation’s data and the building. The main criteria are:
- Load unit and product range: pallet, tote or carton; dimensions, weight and the number of different products.
- Throughput: loads stored and retrieved per hour at peak, and how picking is organised.
- Storage capacity: number of locations needed today and the expected growth.
- Building: a new high-bay building or an existing hall; clear height, floor load capacity and fire protection.
- Availability: how the operation continues if one aisle or machine stops.
- Environment: ambient, chilled or frozen storage.
- Software: how the system connects to the existing WMS or ERP.
A simulation with real order and stock data shows whether the planned number of aisles, cranes or shuttles reaches the required throughput.
Parts of an AS/RS
- Racking designed for the load unit and the building.
- Storage and retrieval machines: stacker cranes, shuttles and lifts.
- Conveyors in front of the rack that bring loads in and take them out.
- Picking stations where goods are brought to the operator (goods-to-person), often with pick-to-light.
- Controls and warehouse control software (WCS) that move each load and manage the storage locations.
- An interface to the WMS or ERP for orders and stock.
Software and integration
The warehouse control software decides where a load is stored, in which order loads are retrieved and how work is balanced between aisles. Good storage strategies, such as spreading fast-moving products across aisles, raise both throughput and availability. The WMS or ERP stays the system that holds orders and stock; the control software executes the movements and reports back.
How an AS/RS project runs
- Data analysis: stock, order structure and throughput are analysed.
- Concept design and simulation: system type, number of aisles and capacity are defined and tested.
- Detailed design: racking, machines, conveyors, electrical systems and software are designed.
- Procurement and installation: racking and machines are supplied and installed.
- Commissioning and ramp-up: the system is tested, stock is moved in and volume is increased step by step.
- Service: planned maintenance, remote monitoring and spare parts keep the system available.
Modernizing an existing AS/RS
Racking and crane structures last for decades, while controls, drives and software age much faster. In a retrofit, the control system, drives, positioning and software are renewed and the mechanical structure stays. The work is planned aisle by aisle, so the warehouse keeps operating during the changeover.
Frequently asked questions
What is the difference between a miniload and a shuttle system?
Both store totes, cartons or trays. A miniload uses one crane per aisle, which gives a steady, moderate throughput. A shuttle system uses shuttles on every level and lifts, so many loads move at the same time; it reaches higher throughput and can be extended more easily.
Can an AS/RS be installed in an existing building?
Yes, if the clear height, the floor load capacity and the fire protection allow it. The building is surveyed during the concept phase, and the system is designed around its limits.
Does an AS/RS replace the WMS?
No. The WMS or ERP continues to manage orders and stock. The warehouse control software of the AS/RS executes the movements and reports the results through an interface.
Can an old AS/RS be modernized instead of replaced?
Yes. When the racking and the mechanical structure are in good condition, the controls, drives and software can be renewed in a retrofit, aisle by aisle, while the warehouse keeps operating.
AS/RS projects at PBC Technology
PBC Technology designs and builds pallet AS/RS, miniload and shuttle systems on a turnkey basis, with its own control and warehouse control software, and modernizes existing systems.