Modeling technology of vacuum pump parts In recent years, with the continuous development of the national economy, vacuum technology has been widely used in the food, pharmaceutical, leather, tobacco, and agricultural product processing industries as jet-pumped vacuum pumps as a vacuum-acquisition device. Compared with other vacuum pumps, it has the advantages of large pumping capacity, stable operation, low maintenance, and simple structure. It is especially common in light chemical production. Therefore, the research and development of injection-type vacuum pump CAD/CAPP/CAM integrated system application software improves the injection efficiency. Pump performance is important for accelerating product development and serialization.

Computer Integrated Manufacturing System (CIMS) is currently a front-of-the-line research topic at home and abroad. Although CIMS has achieved satisfactory and rapid development, traditional geometric modeling systems have many problems that hinder the use of their functions and applications. Promotion. The reason for this is that the modeling systems used by them are points, lines, and bodies with lower levels of abstraction, which do not match the level of abstraction of information used in the design and manufacturing process. In order to realize full integration of CAD/CAPP/CAM, we are not only To consider the expression of geometric information in the CAD system, but also to consider the expression of process information and manufacturing information, and how these information is delivered to CAPP/CAM. In view of the above situation, we adopted a feature-based parametric design method. The computer model constructed using the feature modeling technology, in the information describing the basic structure of the mechanical product, not only includes the geometric information of the part, but also includes a plurality of non-geometric information based on feature part description, and no longer regards the part as Instead of an ordered collection of simple geometric elements, it is obvious that the part is identified as a design entity that is “machined” from certain feature surfaces. Introducing feature modeling techniques into the CAD system can give full play to the functions of the CAD system. Implementing integration with CAPP/CAM systems 1 Part features Model features are the key features of CAD/CAPP/CAM integration. They are integrated units for complete expression of product information. They are a combination of certain shapes, semantics, and abstractions. Feature-based parametric design is Taking manufacturing as the basic feature, its part information model is based on feature database as the basic transmission medium. In order to facilitate CAPP to extract information, and taking into account the separate expression of process information and graphic information, we divide the feature database into parts feature database and features. Two types of pixel database, as shown, in the part feature database, the main record part On the feature information, specifically include the following: 1 shape features: used to describe the geometric shape information with a certain engineering significance, such as the surface shape size, geometric coordinates and the relationship with other surfaces. Including the main features and auxiliary features in two parts, the main features describe the main shape of the parts, and the basic main features and main and auxiliary features make up the basic main features to reflect the blank shape of the segment. In this system, it is mainly a cylinder or a cone. The main and auxiliary features can be seen as integral machining on the basic main features such as rings, threads, cylinders and knurling. It should be noted that, when there are no main and auxiliary features, the main feature types are the same as the basic main features; when there are main and auxiliary features, the main features are the same as the main and auxiliary features. At this time, the basic main features are derived from the main and auxiliary features and the auxiliary features are on the main features. The added modification processing, such as chamfering, drilling, etc. According to the needs of the system, the auxiliary features may include various sub-categories, and each sub-category may be further divided into several sub-categories. Various features are defined by several attributes and feature types.

Accuracy characteristics: used to describe the surface tolerances of the surface to be machined, shape tolerances and surface roughness and other material characteristics: to describe the part of the material type, heat treatment methods and other process characteristics: to describe the part of the process information, such as cutting amount, Features such as processed features, clamping features, positioning features, clamping features, support features, etc.: used to describe part numbers, part name designations, processing workshops, and production lots.

2 Implementation of feature modeling In the CAD system, according to the function of each part of the structural unit of the part, the part is divided into each basic feature. The parameters of each basic feature should include geometric parameters, process parameters and manufacturing parameters. In this way, in the CAD stage, when designing a part, the designer should first input the feature parameters of the part layer and record these parameters in the feature database of the part. Then, the designer selects the parameterized feature maps of different features, and inputs the corresponding parameters of each feature map, and at the same time forms the feature map database of the parts. The geometric shape information, the process information, and the manufacturing information of the parameterized drawings have been passed through. A database file is formed to establish the basis for subsequent CAPP/CAM information extraction. We use the feature data structure of parts to define the parameters of the feature pixels, so that each feature pixel acquires a large amount of non-geometric information during parameter input. And form the corresponding database file. Therefore, the parts assembled from these features have the processing information database required by CAPP/CAM. For example, for the inner surface of the taper hole in a jet vacuum pump, we can use the following data structure definition method (C++ description)/ Part Feature Class/Feature Number/Biological Feature Marking/Male Hole Big End Diameter/Big End Diameter Deviation/Large End Diameter Deviation/Cavity Small End Diameter/Small End Diameter Deviation//Small End Diameter Lower Deviation/Hole Hole Depth/Depth The upper deviation / depth lower deviation / surface roughness / shape insertion point of each basic feature parameter input, in fact, is the process of adding records to the basic feature database and the feature pixel database. Only the parameters of all basic features of each part are After the input, CAD system can form a complete database. Taking a pressure pipe part as an example, the part includes three basic features of an outer cylindrical surface, an inner surface of a tapered hole, and an inner cylindrical surface, as shown, and each basic feature is respectively defined in a corresponding data structure and saved to a feature. In the database, a complete pressure tube signature database is established in this way. 3 Method of setting up a parameterized pixel library The key basis of the feature-based parameterization design is the establishment of the feature pixel library. The process of establishing a parameterized image element library is actually performed. It is the process of constructing the program library, that is, the parametric drawing program for each feature map drawing parameterization drawing program is independent, and each parameterization program of the feature map is called by the feature map element. The parameter input module and drawing module composition feature map element assembly can achieve high quality design intention (because the function of setting up the blish call module is to adopt the form of the dialog box: the type display feature map and call the corresponding according to the designer's intention Parametric drawing program; parameter input module is mainly by the designer interactively input the geometric shape information, process information and Create information parameters; drawing module is mainly used to complete the drawing and merging of each feature drawing element by drawing software, and use the pressure tube of jet vacuum pump as an example to describe the establishment of a parameterized feature pixel library. The characteristics of the tube to complete the design of the pressure tube design, the designer must first enter the parts of the parts characteristics of the database parameters, such as materials, heat treatment methods, technical requirements, production batches, etc., according to the jet vacuum pump pressure tube processing characteristics (The pressure tube is generally composed of a left tube and a right tube, and a complete tube is formed by a welding process.) The left tube consists of (a), (d) two characteristic elements, and the right tube consists of (b), ( c), (e) Three feature pixels, and then enter the corresponding features. 4 Conclusion Based on the parameterized design of the features, the CAPP/CAM required information is directly extracted from the product feature database, which is not only simple and easy, but also solves the geometric modeling. There is no problem with the provided process and manufacturing information, and it effectively reduces possible errors in intermediate data conversion and simplifies the product data transfer process. Provides an effective method for the integration of CAD/CAPP/CAM.

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