# Dynamic Scheduling Optimization of Production Workshops Based on Digital Twin
## 2 The Construction of a High-Quality Virtual Workshop
### Build the Equipment Model  
For some types of intricate machinery, including machining and manufacturing machines, these models typically have a lot of geometric vertices, pieces, etc. A significant performance impact can be placed on the computer when importing to the virtual shop. Light shadows are produced by each model in the scene. The amount of computer resources required by the model increases with its complexity. For the aforementioned reasons, it is necessary to lighten the models before importing them. Table 1 displays the working  
Figure 2: Scanning point and stitching effect. environment for model lightweighting. The model lightweighting tool utilized in this case is the 3D design software Inventor from Autodesk. The model lightweighting steps are illustrated using a five-axis gantry machine in the workshop as a representative example. Some of the components and geometric features of the machine are hidden in the outer surface and have no effect on the machine motion. Fine partial components include screws, bolts, etc. Fine geometric features include holes, rounded corners, chamfers, formed cavities, etc. These parts need to be lightened. The processing process is divided into three steps. 1. Remove redundant geometric features and small components from the model: Inventor provides the function of cladding extraction. This feature simplifies parts by creating cladding on the surface of the part. It provides rule-based part and feature removal to improve capacity and performance in subsequent parts or applications. Use this feature to remove parts that are not visible to the model or within a specified size range, as well as to remove all part features (holes/cavities/rounded corners/chamfers) or part features within a specified size range. 2. Axis assembly downgrade to individual geometry model: The most important assembly component in the gantry machine model is each axis assembly of the machine. However, each axis assembly model may contain other component models, for example, the \(X\)-axis assembly may include motor model, support base model, guide model, etc. The relative relationship between these models is fixed. The relative relationship of these models is fixed. Therefore, in this step, the machine axis component assembly is converted into individual geometry models by the degradation function provided by Inventor. Thus, the individual models in the assembly are fused into a whole, further reducing the number of pieces and vertices in the geometric model. 3. Replace the assembly in the original model with the geometric model after the downgrade conversion: In this step, the replacement parts command provided by Inventor is used to replace the geometric model after the downgrade conversion with the original assembly at the same position, and the original coordinate system of the replaced geometric model overlaps with the original coordinate system of the replaced assembly. The model lightweighting step is achieved by the above three steps. Using a 5-axis gantry machine as the experimental object, the de-lightening step is executed, and it can be visually found that the number of triangular slices is significantly reduced in the display. As shown in Figure 3, a comparison of the density of triangular lamellas after model lightweighting is shown. Table 2 compares several metrics of the geometric model before and after lightweighting. The comparison shows that the number of model slices decreases by 88.82%, the number of vertices decreases by 90.17%, and the number of parts decreases by 91%, which leads to a 92% reduction in model import time. Therefore, the model lightweighting method effectively reduces the computer rendering resources, speeds up the import rate, and provides the foundation for the smooth operation of the virtual workshop. After the lightweighting work was completed, the machine tools were installed according to their positions in the layout and their missing materials were added.