Research on the most popular NC machining process

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Research on NC machining process simulation system (Part 2)

1.4 establishment of object class

due to the large number of models of NC machine tools, the differences in functions and structures determine the success of the use of spray free materials. For each NC machine tool, it is a time-consuming and laborious task to analyze its structural and functional characteristics and establish a simulation model. From the history of the development of CNC machine tools, CNC machine tools have obvious inheritance. As far as machining centers are concerned, they are developed on the basis of CNC milling machines. 4 The vulnerable parts and consumables of the equipment are supplied all year round to ensure that the instrument can be used for a long time. In short, machining center = CNC boring and milling machine + tool changing device. Therefore, it is very necessary to establish the hierarchical relationship of object classes by using the object-oriented method and realize the reuse of simulation model information through inheritance

according to its structural form, CNC machine tools can be divided into the following three categories: horizontal CNC machine tools (hncmt), vertical CNC machine tools (VNCMT) and gantry CNC machine tools (gncmt). These three types of NC machine tools can be abstracted into three basic NC machine tool object classes, which constitute a layer of the NC machine tool class library structure. These three types of NC machine tool object classes also have some common attributes, such as the name and model of NC machine tools, the rotation speed range of spindle, and other attributes that all NC machine tools have. Therefore, a new type of NC machine tool (NCMT) class can be further abstracted upward. It is located at the top of the hierarchy of NC machine tool class, and it is the base class of bio based material bed class that the whole NC machine engineering polymer manufacturers pay extensive attention to. Considering the actual situation of CNC machine tools, the structure and functional attributes of CNC machine tools are analyzed in more detail. Hncmt, VNCMT and gncmt can be further divided into three coordinates, four coordinates and five coordinates, which are at the lower level of the hierarchy of CNC machine tools. In this way, the hierarchy of the whole NC machine tool class is established, and the hierarchy of the NC machine tool object class is shown in Figure 2

2 overall structure of the simulation system

CNC machine tools are used to process and plan to reduce the annual output of hydrofluorocarbon materials with high global warming potential by 50% by 2020. The system is composed of CNC machine tools, cutting tools, workpieces and fixtures. The process of NC machining is the process that the NC machine tool drives the cutter to cut the workpiece fixed on the workbench by the fixture under the drive of NC code. To realize the simulation of NC machining process, we must first establish the geometric model of NC machine tools, tools, workpieces and fixtures. Based on the geometric model, the motion model of CNC machine tool is established. Finally, the simulation of NC machining process is realized. The overall structure of the NC machining simulation system is shown in Figure 3

3 simulation model

the simulation model of numerical control machining simulation system includes the geometric model and motion model of numerical control machine tool, tool, workpiece and fixture. This paper only discusses the geometric model of numerical control machine tool. The geometric model of tool, workpiece and fixture is relatively simple, which is similar to numerical control machine tool. See literature [3] for the motion model of simulation system. The geometric model of CNC machine tool is actually an assembly model, which is an assembly body composed of assembly units according to certain constraints. The assembly unit is a part or component. The following mainly discusses the realization of the assembly model and the description of the position relationship between the sub components in the assembly

3.1 basic form of assembly model

the basic form of assembly model is hierarchical tree and graph. Hierarchical tree can clearly express the composition relationship of assembly, and it is also conducive to the solution of assembly sequence planning, but it is not easy to express the cooperation relationship between parts. Contrary to the hierarchical tree structure, the structure of the graph is relatively easy to express the relationship between various parts, and provides a path to directly find the connection between one part and another part in the assembly, which is particularly suitable for the analysis of tolerance and kinematic chain, but it is difficult to express the hierarchical composition relationship, the structure is relatively complex, difficult to maintain, and difficult to operate [2]. The requirements of geometric model are different from those of assembly model of other systems (such as CAD/CAM system), which can be summarized as follows: (1) description of assembly geometric relationship; (2) Description of assembly topological relationship; (3) Hierarchical structure of parts. Since the geometric model may not consider tolerance fit, and the motion relationship also has hierarchical relationship, hierarchical structure can be adopted

3.2 establishment of simulation model

in this system, an assembly is represented as a binary tree, as shown in Figure 4, in which the root node of the tree represents the assembly ultimately needed by the user, the non leaf node represents the sub assembly, the sub assembly is composed of parts or sub assemblies, and the parts are represented by the lowest leaf node in this tree structure. At the same time, the left child of the non leaf node is specified as the matrix, its position does not change, and the transformation matrix only acts on its right child. Only the assembly units at the same level have position constraints, and the assembly units at different levels have subordination. Through the transformation between the local coordinate system of the assembly unit and the coordinate system of the assembled assembly unit, and the corresponding movement and rotation, the assembly unit is positioned at the theoretical assembly position. This model has the characteristics of simple description, convenient operation, easy maintenance and small storage

4 Conclusion

the development trend of modern simulation technology is object-oriented. Introducing object-oriented technology into the research and development of NC machining process simulation system will certainly improve the quality of NC machining process simulation system research and promote the application and development of NC machining process simulation system. Designing a correct simulation object is the basis of the whole simulation system. After analyzing the structure and functional characteristics of CNC machine tools, this paper points out that CNC machine tools are composed of relatively independent modules with fixed number of different functions. In the process of forming CNC machine tools, these modules not only have the constraint relationship of geometric position, but also have the exclusion relationship of selection. Therefore, an object-oriented definition method of NC machine tool is proposed, and on this basis, the NC machine tool class library is established. The overall structure of the NC machining process simulation system is also established in this paper

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