## 4 Application and Illustrations  
### Application of the Ontology  
Process planning on an LPBF part is carried out to illustrate the application of the developed DL-based ontology. The 3D model of the part is encoded in the STL format and shown in Figure 8. This model is a regular form model, which was developed in [61]. It has 1181 vertices, 2426 triangular facets, total surface area of 9137.33 mm\({}^{2}\), and total volume of 9603.15 mm\({}^{3}\). The bounding box of the model has a length of 74.09 mm, a width of 33.75 mm, and a height of 34.34 mm. It is assumed that the part will be built using the LPBF material Ti6 Al4V and the LPBF machine EOSINT M270. Before starting the actual part build, four process planning tasks on the part, part orientation, support generation, model slicing, and path planning, are needed to be completed successively. The objectives of part orientation are small support volume, short build time, low build cost, small volumetric  
Figure 7: An ontological view of path planning for LPBF. error, and low surface roughness. The used support generation tool is Meshmixer. The objectives of model slicing are normal accuracy and high efficiency. The objective of path planning is high build efficiency. The first task to be completed is part orientation. Based on the information above, two concept assertions _3 dModel_(_modelOfPart1_) and _PartOrientation_(_poForPart1_) and thirteen relation assertions for _modelOfPart1_ and _poForPart1_ shown in Figure 9 were first created. Then, five relation assertions for recommending a part orientation method, which are also shown in Figure 9, were generated after performing OWL/SWRL reasoning using the Drools reasoning engine. According to the reasoning results, the rule-based methods in [61; 62; 63; 64; 65] are recommended to perform part orientation. Here the rule-based method in [65] was used and the determined optimal build orientation under the five objectives is depicted in Figure 8. Based on this, two concept assertions _BuildOrientation_(_obForPart1_) and _UnitVector_(_unitVector1_), a new relation assertion for _poForPart1_, and five relation assertions for _modelOfPart1_, _obForPart1_, and _unitVector1_ shown in Figure 10 were generated in the ontology. Figure 8: 3D model, optimal build orientation, and support structure of an LPBF part. Figure 9: Assertions and reasoning results of part orientation for the LPBF part. The second task to be completed is support generation. In this task, a concept assertion _SupportGeneration(sgForPart1)_ and seven relation assertions shown in Figure 11 were first created. Then, support generation was carried out using Meshmixer and the generated support structure is depicted in Figure 8. Based on this, two new relation assertions for _modelOfPart1_ shown in Figure 11 were generated in the ontology. The third task to be completed is model slicing. Firstly, a concept assertion _ModelSlicing(msForPart1)_ and nine relation assertions shown in Figure 12 were created. Then, a relation assertion for recommending a model slicing strategy, which is also shown in Figure 12, was generated after performing OWL/SWRL reasoning using the Drools reasoning engine. According to the reasoning results, ussd (uniform slicing in single direction) can be selected to slice the build model with a thickness of 0.03 mm. Based on this, a new relation assertion for _msForPart1_ and three relation assertions for _slicesOfPart1_ shown in Figure 12 were generated in the ontology. The last task to be completed is path planning. Firstly, a concept assertion _PathPlanning(ppForPart1)_ and nine relation assertions shown in Figure 13 were created. Then, a relation assertion for recommending a laser scanning path, which is also shown in Figure 13, was generated after performing OWL/SWRL reasoning using the Drools reasoning engine.