0 Preface The CNC machine tool is a device that processes workpieces according to a pre-programmed machining program. The processing program must not only ensure that the machined workpiece meets the requirements of the drawings, but also makes the functions and performance of the CNC machine tool as fully as possible. Therefore, the processing is performed. It is of great significance to run the program for graphical simulation to verify the correctness of the machining program. Not only that, CNC machining simulation training has received more and more attention from people. This is because NC machining requires operators to be familiar with NC programming instructions, CNC functions, and the performance of CNC machines. These characteristics of CNC machining determine the traditional Technical training methods can no longer meet the needs. The so-called traditional technical training means that the operators first learn technical theories and operating procedures, then go to the production site, and use the way the master trains the apprentices for skills training. The main disadvantage of this method is that CNC machine tools are generally more expensive equipment, and students are not allowed to randomly start, stop, and create accidents. Therefore, students will have fewer mobile phones and students will have longer operational skills. In addition, the level of masters is uneven, and the quality of teaching is difficult to guarantee. Therefore, the NC machining simulation plays an important role in the correctness of the inspection processing program and the training of operators. This article takes the widely used numerically controlled boring and milling machine and machining center as the research object, and mainly discusses the use of object-oriented technology to analyze the numerical control machine tools, and establishes the numerical control machine tool object classes and simulation models. The numerical control machine tool referred to in this article is a general term for CNC boring and milling machines and machining centers. 1 Object-Oriented Technology in Simulation Systems Object-oriented technology describes and handles objects in the real world. Its data abstraction, inheritance, and polymorphism mechanisms are particularly suitable for describing complex objects with intrinsic mechanisms, and thus have been widely used in various industries. 1.1 Object-Oriented Technology In object-oriented technology, an object with the same structure and processing mechanism is abstracted as a class, and an object is an instance of a class. Objects not only have states or attributes described by data, but also have operations for changing the state of objects (in object-oriented, these operations are called methods), which realizes the combination of data and operations, and thus, objects can describe the structure of things at the same time. Information on both aspects of behavior and behavior. Different objects are completed by message passing, and the internal data operations of the object are not visible to the outside. This is called data encapsulation. The object-oriented object inheritance mechanism allows the properties of a parent class to be passed to subclasses through inheritance. This feature provides possibilities for describing objects in the objective world. Object inheritance is very useful for solving the resource sharing between objects and improving the reusability and extensibility of software, and the reusability and extensibility of software products maintainability. It has a great influence on the quality and productivity of replacement products. In object-oriented technology, determining the derivation relationship between objects is the key to establishing the entire system. The entire system often has only one or a few basic object base classes, and the rest are base class derived classes. The derived relationship of object-oriented technology allows us to directly obtain a large number of ready-made properties and methods from existing classes, and its polymorphic properties allow us to define properties and methods in the derived class that are different from the base class. 1.2 Object-Oriented Analysis of CNC Machine Tools Although the structure of CNC machine tools is complex, they are all composed of relatively independent and fixed modules with different functions. The object-oriented method is used to analyze CNC machine tools. The specific CNC machine tools and modules are regarded as objects. Independent of various objects, Figure 1 shows the object model of CNC machine tools. In the object model, the CNC machine tool consists of a spindle, a column, a bed, a work table, a control panel, a tool changer, and a pallet changer. It is slightly different from the composition of the actual simulation object. Some non-simulation-related components, such as the hydraulic system and the electrical system, may not be considered in the simulation model to simplify the simulation model. The black ball points "·" and "l ten" in the figure are multiple symbols, indicating that many instances of a class are related to instances of another class, and an empty ball point "O" indicates 0 or 1 instance correlation of a class. For another class instance. As can be seen from the object map, the main shaft, main column, bed, workbench, and control panel are necessary for each CNC machine tool. The tool changer and the pallet changer are optional components, but for the machining center Tool changer and pallet changer are also required. 1.3 Exclusion Checking The CNC machine tool is not an arbitrary combination of all parts. The selection and match between parts have a certain exclusion relationship. The simulation system must be able to describe these exclusion relations to ensure that the simulation model reflects the actual existing CNC machine tools. For example, in the tool changer, the robot is an optional component, and the magazine is an essential part, but once the chain magazine is selected, a robot must be selected; the machining center can have multiple magazines, but it must be a robot. In order to complete the tool change operation, the worktable and the tray device also have an exclusion relationship. The rectangular worktable cannot be equipped with the tray device on the same CNC machine tool; the movement of the base of the indexing table determines the index table and The relationship between the type of tray device, the base fixed indexing table can only be used with the rotary tray device, and so on. Since there is only an exclusion relationship between components in a simulation system, and the number of component types is limited (but each component type is infinite), each component type can be given a certain ID number in advance. According to CNC machine tool specification standards, there are fewer types of CNC machine tools, and the simulation system can enumerate all the ID numbers in each CNC machine tool that have an exclusion relationship. The exclusion relationship is described by a set. Let A and B be two sets. a1, a2, ..., an represent the ID numbers of the components of the numerically-controlled machine tool, which are the elements of the set A. b1, b2, ..., bm also represent IDs of the parts of the numerically-controlled machine tool. The number is the element of the set B, ie, A={a1,a2,...,an} B={b1,b2,...,bm} then the exclusion relation in the simulation system can be expressed as: the set A excludes the set B, or the set B excludes the set A, that is, if a certain simulation model, all elements of the set A and B exist, indicating that there is a component exclusion in the model, you need to reselect the component type. 1.4 The establishment of object classes Due to the large number of CNC machine tools and their differences in function and structure, it is a time-consuming and laborious task for each CNC machine to analyze its structural characteristics 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 boring and milling machines. In simple terms, machining centers are equal to CNC boring and milling machines. Therefore, using the characteristics of similarity in the structure and function of CNC machine tools, it is necessary to use object-oriented methods to establish the hierarchical relationship of object classes and to reuse the simulation model information through inheritance. The classification of CNC machine tools based on their structure is relatively simple and can be divided into the following three categories: horizontal CNC machine tools (HNCMT), vertical CNC machine tools (VNCMT), and gantry CNC machine tools (GNCMT). The three types of CNC machine tools can be abstracted into three basic types of CNC machine tools, which form a layer in the library structure of CNC machine tools. These three categories of CNC machine tools also have some common attributes, such as the name, model number, and spindle speed range of the CNC machine tool, which all have the attributes of a CNC machine tool, so that a new class can be further abstracted upwards--NC. Machine Tool (NCMT), which is at the top of the hierarchical structure of CNC machine tools, is the base class of the entire CNC machine tools. Considering the actual situation of CNC machine tools, the structure and function attributes of CNC machine tools are analyzed in more detail. HNCMT, VNCMT, and GNCMT can be further divided into 3 coordinates, 4 coordinates, and 5 coordinates. They are in the category of numerical control machine tools. The lower level of the hierarchy. In this way, the hierarchical structure of the entire CNC machine tool class was established. The hierarchical structure of the NC machine tool object class is shown in Figure 2. 2 The overall structure of the simulation system CNC machining system consists of CNC machine tools, cutting tools, workpieces and fixtures. The process of numerical control machining is a process in which a numerical control machine tool drives a tool under the drive of an NC code to perform machining on a workpiece that is fixed on a workbench by a clamp. To realize the simulation of the NC machining process, we must first establish the geometric model of CNC machine tools, tools, workpieces and fixtures. Based on the geometric model, the motion model of CNC machine tools was established. Finally, the simulation of the 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 CNC machining simulation system includes the geometric model and movement model of CNC machine tools, tools, workpieces and fixtures. This article only discusses the geometric model of CNC machine tools, and the geometric model of tools, workpieces and fixtures is relatively simple, similar to that of CNC machine tools, simulation system. The model of motion can be found in [3]. The geometric model of a CNC machine tool is actually an assembly model. It is an assembly unit in which the assembly units are combined with certain constraints, and the assembly unit is a part or a component. The following mainly discusses the realization of the assembly model and the description of the positional relationship among the sub-components inside the assembly. 3.1 The basic form of the assembly model The basic form of an assembly model is a hierarchical tree and a graph. Hierarchical trees can clearly express the composition of assembly, but also help to solve the assembly sequence planning, but it is not easy to express the relationship between parts. Contrary to the hierarchical tree structure, the structure of the figure is relatively easy to express the relationship between the parts, and provides a direct path from one part to another in the assembly, especially for tolerance and kinematic chain analysis. Difficult to express the hierarchical composition, the structure is more complex, difficult to maintain, and the operation is more difficult [2]. The requirements for the assembly model of geometric models and other systems (eg, CAD/CAM systems) are different and can be summarized as: (1) description of assembly geometry; (2) description of assembly topology; (3) construction of part hierarchy. Since the geometric model may not consider the tolerance coordination, and the motion relationship also has a hierarchical relationship, a hierarchical structure may be adopted. 3.2 The establishment of a simulation model In this system, an assembly is represented as a binary tree, as shown in Figure 4, where the root node of the tree represents the assembly the user ultimately needs, the non-leaf node represents the sub-assembly, the sub-assembly is the part, or The sub-assembly is composed of parts in this tree structure represented by the lowest level of leaf nodes. At the same time, the left child of the non-leaf node is defined as the base. Its position does not change, and the transformation matrix only affects its right child. Only the assembly unit of the same level has the “positional constraint†relationship, and the assembly units of different levels have the “subordination relationshipâ€. The assembly unit is positioned at the theoretical assembly position by converting the assembly unit's local coordinate system and the coordinate system where the assembly unit is assembled, and the corresponding movement and rotation. 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 research on NC machining process simulation system and promote the application and development of NC machining process simulation system. Designing a correct simulation object is the basis of the entire 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 and fixed modules with different functions. In the process of forming CNC machine tools, these modules not only have the constraint of geometric position, but also There is an exclusionary relationship to use. Therefore, an object-oriented method for the definition of numerical control machine tools is proposed, and on the basis of this, a numerical control machine tool library is established. The overall structure of the numerical control processing process simulation system is also established in the article. Yamaha Series Ignition Switch,Highest Grade Motorcycle Ignition Switch,Motorcycle Ignition Switch Kit For Yamaha,Motorcycle Ignition Switches Keys Zhejiang Lisheng Motorcycle Parts Co.,Ltd , https://www.lishengmotorparts.com
