# A Scheduling Algorithm for Multi-Workshop Production Based on BOM and Process Route
## 2 Analysis of Scheduling Problems for Complex Products in Multi-Workshop Production  
Traditional workshop scheduling takes the workpiece or product as the minimum production object. The workpiece is first processed by the manufacturing workshop, and when the processing is completed, it enters the assembly workshop, where the end products are finally produced. In this way, the two processes of product processing and assembly are handled separately, as shown in Figure 1. Figure 1a shows that the workpiece or product is processed and manufactured according to its process, and Figure 1b illustrates that the product is assembled and produced according to its assembly relationship. However, in actual production, it often involves a large number of complex products. These products are assembled from multiple workpieces or sub-assemblies. There are complex dependencies between the various components or sub-assemblies of the products. The production processes also need to go through multiple workshops and involve the processing and assembly processes. There are sequence constraints between the multiple processes involved. Figure 2 shows an example of a complex product composition. For the production scheduling of these products, if the processing and assembly processes are considered separately and the scheduling optimization is unilateral, the parallel mechanism of the product production process and the inherent relationship between its components will be destroyed, making the integration of product processing and assembly processes impossible. Therefore, for the production of complex products, if there are many types of products and they need to go through multiple workshops, the scheduling task can be transformed from a general scheduling problem to a complex scheduling problem in multi-workshop production.  
Figure 1: Product processing and assembly process. (**a**) Product/workpiece manufacturing process flow, (**b**) Product assembly composition relationship.  
Figure 2: Composition of a complex product assembly.  
For example, the following research topics emerge:  
* Finishing all scheduling tasks as early as possible in a multi-workshop environment;
* Allocating processes reasonably to make equal use of workshop resources when multiple workshops have similar device resources;
* Optimizing scheduling when products have different delivery cycle requirements;
* Carrying out reasonable batching and scheduling when the product scale is large.  
The object under study in research on the complex product scheduling problem is the product with complex constraints in a multi-workshop environment. The product is of multi-variety and small batch and has a complex structure. Its scheduling mechanism is the integration of processing and assembly processes. The problem of complex product scheduling in a multi-workshop environment has not only a general constraint relationship between processes but also correlations between products. Therefore, it is necessary to consider the process transfer problem caused by the processing of products not in the same workshop, as well as the reference and constraint issues between different products and the different delivery cycle requirements. This research studies the scheduling problem of complex products. This paper constructs a model of the complex product scheduling problem, which is formulated with the minimum delivery cycle as the optimization goal. An improved particle swarm algorithm is used to solve the optimization problem, and the effectiveness of the algorithm is verified by a case study.