Complete Application of Stacker Cranes in Automated Storage and Retrieval Systems (AS/RS)

A stacker crane, also known as a rail-mounted aisle stacker crane, is the core operating equipment in an automated storage and retrieval system (AS/RS). It handles the entire process of automated goods storage, retrieval, relocation, and inventory management within the racking aisles. Relying on horizontal movement, vertical lifting, and fork extension/retraction, it achieves precise storage and retrieval. It is a standard piece of equipment in manufacturing, logistics, pharmaceuticals, and cold chain intelligent warehousing.

I. Core Structure and Motion Principle of Stacker Cranes

A complete stacker crane consists of four main mechanisms operating in tandem:

1. Traveling Mechanism (X-axis): High-speed reciprocating along the aisle via overhead and ground rails, at a speed of 60–160 m/min;

2. Lifting Mechanism (Y-axis): Vertical lifting of the loading platform, adaptable to 7–45 meter high-rise racks, with a lifting speed of 20–40 m/min;

3. Fork Extension Mechanism (Z-axis): Single/double-deep telescopic forks, extending into the storage location to access pallets/bins, with a positioning accuracy of ±5 mm;

4. Onboard Electronic Control System: Onboard PLC, wireless communication, multiple safety detections (overheight/overwidth/rope breakage/collision-proof light curtain), and interface with the warehouse WCS dispatch system.

II. Mainstream Classifications and Corresponding Application Scenarios of Stacker Cranes

1. Classification by Storage Unit (Most Commonly Used)

(1) Pallet Stacker Crane (Mainstream Heavy-Duty)

• Double-Column Heavy Duty: Load capacity 1–5t, height 15–45m, strong rigidity, stable operation

Applications: Automotive parts, finished home appliances, chemical raw materials, cold chain pallets, ton bags, heavy machinery parts warehouse

• Single-Column Light Duty: Low self-weight, low cost, load capacity 0.3–1.5t, height ≤15m

Applications: 3C electronics, small auto parts, clothing pallets, raw material warehouses of small and medium-sized factories

(2) Miniload Box Stacker Crane (Dedicated for Light and Small Items)

Storing and retrieving bins, turnover boxes, cartons, load capacity 5–50kg, faster speed, higher precision

Applications: Pharmacies, e-commerce small item sorting, electronic components, precision parts buffer, file storage

2. Classification by Fork Depth

• • Single-depth stacker crane: One row of storage positions on one side, fast access, simple scheduling, ideal for scenarios with many SKUs and frequent inbound/outbound operations;

• Double-depth stacker crane: Extended forks, two rows of storage positions on one side, nearly doubling storage density, suitable for large-volume, low-SKU raw material warehouses.

3. By aisle capacity

• Straight-rail standard stacker crane: One crane per aisle, stable and efficient, suitable for most standard vertical warehouses;

• Rail-changing/turning stacker crane: One crane can operate across multiple aisles, with lower aisle throughput, shared across multiple aisles, reducing equipment investment.

III. Standard Operating Procedures for Stacker Cranes in Automated Warehouses

1. Inbound Process

1. The forklift places the goods on the inbound conveyor platform and scans the barcode to enter the data into the WMS (Warehouse Management System);

2. The WCS (Warehouse Control System) issues a task to the stacker crane;

3. The stacker crane moves to the inbound entrance → receives the goods on the loading platform → lifts and lowers to the target layer → the forks extend into the storage location to store the goods;

4. The task is completed and reported back to the system, and the inventory is automatically updated.

2. Outbound Process

1. The order is placed, and the WMS locks the target storage location;

2. The stacker crane arrives at the storage location, the forks remove the goods → it descends to the outbound platform;

3. The goods are transferred to the sorting area/production line via the conveyor line, completing the shipment.

3. Composite High-Density Warehouse Supporting Process (Stacker Crane + Shuttle Car Combination)

The stacker crane handles layer-by-layer transfers and aisle transport, while the shuttle car handles deep, high-density storage within each rack level:

Inbound: The stacker crane delivers pallets to the corresponding level → the shuttle car transports them to the deep storage location;

Outbound: The shuttle car retrieves goods to the aisle entrance → the stacker crane receives the goods and transports them out of the warehouse.

Advantages: Increases storage density by 30%, accommodating both high-level and high-density storage, suitable for large-volume raw material storage.

---BY ZITA JIAN

7th, July 2026