AutoCAD is the most widely used CAD graphics support platform, but lacks parametric design functions, so it can not complete the automatic design and drawing of components, and the design efficiency is difficult to improve. This research focuses on the development of computer-aided design software for the secondary cylindrical gear reducer for professional users. By inputting working parameters (such as transmission power and speed), the parametric design of the key components of the reducer and the management of the parts library can be realized. And computer-aided process analysis, etc., to help the computer aided design and manufacturing of the reducer.
1 Reducer CAD system constitutes the structure of the reducer CAD system.
The parametric design module of the component completes the parametric design function of key components (such as gears, shafts, etc.) in the reducer. For gear parts, the system can according to the input parameters (such as gear transmission power, drive gear speed). , transmission ratio, number of gears of the driving gear, etc.), automatically complete the structural design of the gear, and output a two-dimensional engineering drawing.
The library management module mainly establishes the parts database, realizes the functions of warehousing, editing, modification and query of the part graphic data information, thereby realizing the computer management of the parts library.
The computer-aided process analysis module analyzes and processes various information and production data of parts and components, and provides a list of process data and resources that can be directly accepted by the production, thereby accelerating the design of process specifications and achieving resource optimization.
2 Component Parametric Design Module The cylindrical gear reducer has many components. This system has developed a parametric design module for the main components such as gears and shafts. The standard spur gear is taken as an example to illustrate the implementation method of component parametric design.
2.1 Component Parametric Design Module Composition According to the gear design method, the system is designed according to the gear parameters.
Soft toothed closed gear drive. The main failure mode of the gear is the tooth surface fatigue pitting. The design should first calculate the pinion diameter according to the tooth surface contact fatigue strength, and then use the root bending fatigue strength to check.
Hard toothed closed gear drive. The main failure mode of the gear is the bending and fracture of the tooth root. The design should first calculate the modulus according to the bending fatigue strength of the tooth root, and then check the fatigue strength of the tooth surface contact.
To facilitate user interaction with the system, the system should have a friendly user interface. The input of the known parameters is implemented by a "text box", and the calculated result data is output in the "tag".
2.2 Programmatic processing of data The calculation of gear geometry is one of the key steps in implementing parametric design. The calculation process and calculation formula can be referred to the relevant manual and system literature. In the process of gear design, you need to find a large number of charts.
According to whether the data source is in the form of discrete table or continuous curve, the system uses different algorithms to realize the automatic query function of related parameters.
For the discrete table form, such as the tooth width coefficient Ψd, first store the tooth width coefficient data under different conditions in a static array, and then use VB to write a program to query the table and directly call the relevant data.
For the continuous curve form, if the load concentration coefficient Kβ is a continuous curve of the tooth width coefficient Ψd, the data is first discretized, and the tooth width coefficient Ψd takes a value of 0.1 to Kβ and is stored in a static array. In the actual programming query, the interpolation method is used according to the specific value of Ψd.
2.3 Drawing of part drawing By creating a reference to an AutoCAD part object, the VB language can realize the function of creating an AutoCAD file and drawing a part drawing.
3 Gallery Management Module In addition to the main components such as gears, shafts and cabinets, the reducer consists of numerous accessories (such as ventilators, lifting rings) and standard parts (such as bearings and bolts), in order to achieve the engineering drawings of these parts. Designed and developed this module for unified classification management. The library management module should implement the following functions: add, delete, and modify the graphic file library; edit and query the part information; browse and print out the specified part drawing.
3.1 Gallery Management Module Design Process The AutoCAD Gallery Management Module mainly includes the creation of basic graphics library, statistics of related data information, interface design and implementation of management procedures. The library management module design is mainly divided into two parts: one is to use Access to create a part information database, and the other is to use VB to write a program to realize the unification of AutoCAD graphics and related information.
3.2 Database Creation Microsoft Access is used to create a database of parts related information, including part number, pattern name, mapper, reviewer, material, warehousing time and modification time.
3.3VB program to the database call program interface is mainly composed of three areas: information display area, picture preview area, function button area, as shown in Figure 3.
The information display area is used to display related information of parts in the gallery; the image preview area displays AutoCAD graphic files; and the function button area is used to implement operations such as querying, modifying, and deleting part drawings.
4 Computer Aided Process Analysis Module The computer aided process analysis module provides a list of data and resources for the process to speed up process design and increase production efficiency. This module consists of 4 sub-modules, which not only has the function of typical part processing technology data management, but also can automatically generate process cards. The flow of the system.
4.1 Process Database Management The sub-module needs to be applied to a large amount of data such as machining material data, machine tool data, fixture gage data, etc. in the process of generating part process specifications. The process data of the system mainly includes processing material data, and using Access technology to create a related process database for the system to operate. The process database management sub-module can implement update management such as adding, modifying, and deleting the above data.
4.2 Process query sub-module Query operations on relevant process data, such as machine data, shape and position tolerance data, etc. In addition, it also includes common machining processes, common machining routes, and machining accuracy.
4.3 The process editing sub-module edits the machining process of the part. For example, the modification of the machining process, processing route and machining accuracy, the sub-module also has the functions of information addition, information deletion and data maintenance.
4.4 The process card generation sub-module manages, queries, and edits the existing process routes, and can generate new process cards according to the part structure.
5 Conclusion This system uses VisualBasic as a development tool to carry out secondary development of AutoCAD, and realizes the parametric design of the two-stage cylindrical gear reducer, the management of the parts library and the computer-aided process analysis. The design has achieved functional modularization and graphical programming, providing reference for the realization of the integrated CAD/CAM/CAPP of the reducer.
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