## 1 Introduction  
The production of medical consumables is characterized by high variety, small batch sizes, multiple production cycles, and a high degree of customization [1, 2]. These features present considerable challenges for manufacturing enterprises in workshop scheduling. On one hand, the frequent and small-batch nature of orders fragments production tasks, increasing the complexity of equipment changeovers and production scheduling [3]. The high level of customization limits the applicability of standardized processes, introducing significant uncertainty into the manufacturing system [4]. Collectively, these factors reduce production line utilization and elevate the risks of delivery delays and inventory accumulation, forming a critical bottleneck that constrains the operational efficiency of medical consumable manufacturers.  
To address the aforementioned challenges, order splitting and reorganization methods have been widely applied in the manufacturing of medical consumables [5, 6]. Order splitting decomposes large orders into multiple sub-tasks to enhance production flexibility,while order reorganization optimally integrates these sub-tasks to improve resource utilization. However, existing methods still exhibit several limitations. First, most approaches focus on a single optimization objective, either order splitting or reorganization, without considering their synergistic optimization [7]. Second, current methods rarely incorporate multi-dimensional and multi-scale constraints, such as different product specifications, production batches, and resource matching, which limits their adaptability to complex manufacturing environments [8].  
Therefore, this study proposes a multi-dimensional, multi-scale bi-level collaborative optimization method for order splitting and reorganization in the manufacturing of medical consumables. A bi-level optimization model is developed, in which the upper level optimizes the order splitting strategy, and the lower level optimizes the reorganization of production tasks to ensure efficiency and rationality in the manufacturing process. The model comprehensively accounts for order characteristics, production resource constraints, and delivery requirements, and it is solved using a bi-level multi-objective optimization algorithm to balance production costs and delivery time. The main contributions of this study are as follows:  
1. A bi-level collaborative optimization model for order splitting and reorganization is developed to address the limitation in existing studies that treat these processes independently.
2. The model considers the multi-dimensional and multi-scale characteristics of medical consumables, which are often overlooked in prior research, enhancing its adaptability and practical applicability.
3. A bi-level hybrid multi-objective optimization algorithm is proposed to solve the model efficiently, filling the gap in the literature where most optimization methods remain single-layered or single-objective.  
The remainder of this paper is organized as follows: Section 2 presents a literature review, analyzing the current research status and limitations of existing order splitting and reorganization methods. Section 3 establishes the bi-level optimization model for order splitting and reorganization. Section 4 presents a bi-level hybrid multi-objective optimization algorithm for solving the model. Section 5 verifies the effectiveness of the proposed method through a case study. Finally, Section 6 concludes this study and outlines directions for future research.