Comparing the 3 Main Automatic Case Storage & Retrieval Systems
Guest blog by MHI member NūMove Robotics & Vision
As automation and warehouse operations continue to advance, three solutions are widely recognized for their performance and innovation in automated case storage and retrieval systems (ASRS): mini-load ASRS using cranes, case shuttle ASRS, and motor-driven conveyor ASRS. Each system offers distinct characteristics and advantages, making them ideal for specific cases. This overview explores how these technologies work and highlights the key pros and cons of each approach.
Mini-Load ASRS Using Cranes
Crane‑based mini‑load ASRS relies on stacker cranes to store and retrieve cases to or from designated rack locations. This solution is valued for its adaptability, as it can manage products with a wide range of dimensions and weights. Although its storage density is lower than that of case shuttle and motorized conveyor ASRS, it stands out for its ability to handle heavier loads. A key limitation is the strong link between throughput and capacity: increasing performance typically requires expanding storage space, and the opposite is also true. In most applications, a single mini‑load crane is capable of handling approximately 100 to 120 inbound and outbound moves per hour.
ASRS Using Case Shuttle
Case shuttle ASRS uses autonomous shuttle vehicles: compact, wheeled units that move along storage aisles to retrieve and deposit cases at precise locations. This solution delivers a greater storage density than crane‑based mini‑load ASRS, although it does not reach the density levels offered by motorized conveyor ASRS. One of its main strengths is scalability in performance: system throughput can be increased by adding shuttles without the need to expand overall storage capacity, making it ideal for operations where speed and volume of movement are the primary drivers. Based on configuration and shuttle quantity, a case shuttle ASRS can typically handle up to 1,000 ins and outs per aisle per hour.
ASRS Using Motorized Conveyor
Motorized conveyor ASRS uses powered conveyor lanes to automatically store and retrieve products. Among the three solutions, it delivers the highest storage density since it operates without aisles. Items can be introduced at one side and discharged at the opposite side, or both loading and unloading can occur from the same end. This system is capable of handling approximately 1,400 inbound and outbound movements per hour per level, which makes it particularly well suited for high‑velocity SKUs. That said, expanding storage capacity requires adding more buffer lanes at each level, while increasing throughput calls for additional levels. Compared with the other ASRS technologies, motorized conveyor ASRS also imposes stricter constraints on product dimensions, as item length must align with the physical limits of the buffer lanes and their supporting structure.
Key Advantages of Case AS/RS:
• Optimized High‑Density Storage: Make the most of both vertical and/or horizontal space to minimize facility footprint while expanding storage capacity.
• Efficient Material Flow: Automated case handling accelerates order fulfillment, even under high‑volume or peak‑demand conditions.
• Increased Operational Productivity: By reducing or eliminating manual travel, operators save time on every picking and replenishment task.
• Improved Accuracy and Dependability: Smart control systems provide end‑to‑end traceability and significantly lower the risk of human error.
• Seamless Software Connectivity: Easily integrates with WMS, WCS, and ERP systems to coordinate inventory control, order execution, and real‑time operational decisions.
Conclusion
Every automated storage and retrieval solution comes with its own advantages and trade‑offs. Crane‑based mini‑load ASRS stands out for its versatility and ability to manage heavier loads, though it delivers comparatively lower storage density and operating speed. Case shuttle ASRS achieves greater density and higher throughput, but optimal performance depends on accurately sizing and balancing the number of shuttles in the system. Motorized conveyor ASRS leads in both density and throughput; however, it is more restrictive in terms of product dimensions and requires the addition of buffer lanes or extra levels when scaling capacity or performance.
Choosing the most suitable ASRS solution depends on a clear understanding of your operational priorities. Whether your focus is adaptability, processing speed, or maximizing storage utilization, selecting the right technology can significantly improve warehouse efficiency and overall system performance.
