Performance & Economic Evaluation of Puzzle-based Movable Rack Systems

The key trade-off in selecting storage and order-picking systems lies between maximizing storage density, achieving high system throughput, and managing costs. Puzzle-based storage (PBS) systems excel in storing unit loads at extremely high density by eliminating the need for traditional aisles. However, these systems require each load to be placed on a moving device, such as a conveyor module or transport vehicle, making them costly to construct and maintain. Additionally, achieving high throughput in PBS systems poses a significant challenge due to their compact design and reliance on dynamic load movements. This paper focuses on a recently explored solution known as the Puzzle-Based Movable Rack (PBMR) system, which enhances traditional puzzle-based storage by equipping racks with autonomous wheels. While previous studies have explored the throughput potential of PBMR systems using analytical models, this study primarily contributes by conducting a detailed economic evaluation of PBMR systems under different throughput requirements. We assess their cost-effectiveness compared to conventional storage systems and analyze how system configurations impact both operational efficiency and feasibility. Our findings indicate that PBMR systems can achieve competitive throughput levels with optimized configurations while offering cost advantages in specific scenarios.