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Automated warehouse: AS/RS, shuttle or block storage – which system suits you?

Anyone planning an automated warehouse today faces a fundamental choice: stacker crane (AS/RS), shuttle system or compact block storage like AutoStore? All three have their place – what matters are your requirements for throughput, storage density and budget.

A common misconception up front

The choice is often reduced to "AS/RS for pallets, shuttle for totes." That is wrong: both systems exist for pallets as well as for totes. Whether pallet high-bay warehouse with a stacker crane, pallet shuttle, mini-load AS/RS or tote shuttle – the unit load does not distinguish the systems. The real difference lies elsewhere: in throughput and cost.

AS/RS – the proven all-rounder

A stacker crane serves an entire aisle on its own – vertical and horizontal movement in a single machine.

Strengths:

• Building heights of 45 m and more – maximum capacity on a small footprint
• Robust, mature technology with comparatively simple controls
• Lower investment per storage location at moderate throughput needs
• Few machines = manageable maintenance

Limits:

• Throughput per aisle is limited by the single machine
• If the crane fails, the whole aisle stops

A good fit when high storage capacity is required but throughput stays moderate.

Shuttle – dynamics through scaling

In a shuttle system, many vehicles work in parallel across several levels, while lifts handle the vertical transport.

Strengths:

• Very high throughput – scalable via the number of shuttles
• Redundancy: if one shuttle fails, the system keeps running
• Flexibly adaptable to building geometries

Limits:

• Higher investment: vehicles, lifts and intermediate platforms cost money
• More complex controls and more demanding maintenance of many individual vehicles
• Intermediate platforms reduce the usable levels for a given height

A good fit when throughput is the decisive factor – for example in e-commerce or with pronounced peaks.

In short: AS/RS vs. shuttle

Choosing between AS/RS and shuttle is at its core a throughput-versus-cost calculation: the stacker crane delivers capacity at lower cost, the shuttle delivers performance – at a higher price. Anyone who knows their order structure and peak loads can set up this calculation cleanly.

Block storage (e.g. AutoStore) – maximum density

Block storage does away with aisles entirely: totes are stacked directly on top of one another, and robots travel across a grid above them and lift the totes out.

Strengths:

• Highest storage density on the market – no aisle losses, up to 4x the density of classic systems
• Picking directly integrated: the robots deliver the totes straight to the ports – goods-to-person without additional conveyor technology
• Modularly expandable, even during operation
• Ideal for existing buildings with low ceiling height

Limits:

• Floor properties: the grid places high demands on the flatness and load-bearing capacity of the floor
• Fire protection: the compact stacking makes sprinklering and firefighting within the block harder – insurers and authorities look closely
• Suitable for totes only, with limited tote size and weight
• Accessing deeply stacked totes requires re-stacking – which costs performance with poor sorting

A good fit when small parts are to be stored on minimal space and picked directly.

Conclusion: there is no "best" system

The right choice depends on your order structure, your article range, your building and your budget. As an independent consultant, I compare the systems neutrally – vendor-independent and based on your figures.