Development and Application of Hob Design and Manufacture Expert System

The wide application of computer technology in the machinery industry has triggered a tremendous transformation in the way traditional machinery design and manufacturing. In the field of gear manufacturing, the emergence of new methods of hob design and manufacturing and the productization of CNC high-speed hobbing machines, making hobbing technology The rise to a new level has placed higher demands on the design and manufacture of hobbing cutters. The traditional approximate calculation method commonly used in production and the technique of mechanical dressing wheel dresser grinding wheel are difficult to meet the hob design. The need for manufacturing technological advancement. On the other hand, with the deepening of the reform of the teaching system in universities, there are more and more people who understand computers in the engineering and technical personnel of China, and personnel who have mastered complex tool design and manufacturing techniques will gradually reduce. System technology, development of practical gear hob design and manufacture of expert systems, has become an important way to develop gear hob design and manufacturing technology.
This study derives the general formula for gear hob-edge and shovel-sharp contours, integrates the experience of experts in the field, combines symbolic reasoning and numerical calculations organically, and develops a practical expert system for hob design and manufacture. (HDMES). The system uses C language to compile the calculation program, use AUTOCAD to automatically draw and output, use VP_Expert to build expert system knowledge base and achieve consultation and interpretation functions, and use VB to develop a friendly system integration interface.

1 General formula for calculation of hob edge and shovel frosted outline

In order to reduce the workload of the expert system development and increase the versatility of the system, the author successfully derived the calculation formula for the hob-edge and shovel-sharp profile. For any tooth-shaped workpiece, only a complete tooth-shape dispersion is required. Turning to a list curve, you can use the hob to calculate the formula to calculate the shape of the hob, and then calculate the shape of the shovel's matte based on the shape of the hob. Then, the system draws a hob edge and shovel frost outline on the screen (eg, Figure 1 shows that at the same time, the shovel outline shape is stored in a database in a certain format for the FGS_30N CNC forming grinding machine to automatically generate the shovel grinding wheel dressing software, dressing the grinding wheel and grinding the hob.

Figure 1 hob edge and shovel frosted outline
Fig.1 Profiles of hob tooth and relief grinding wheel

The hob-edge calculation formula is derived by combining the space medium rack method and the tooth profile normal method. As long as the coordinate value of the workpiece tooth point represented by the discrete value and the unit tangent of the point are provided, the calculation pass can be used. The axial blade shape of the hob is calculated by the formula. For the standard straight groove zero-front hob, it is the rake face. The calculation example shows that the formula has a calculation accuracy of 0.1 μm and can fully satisfy the hob. Design and manufacturing engineering requirements [1].
At present, tool designers usually only perform hob design without considering hob manufacturing problems. However, for any gear hob, the calculation of scoop outline shape is very important. The development of a gear hob design and manufacture expert system cannot It does not solve the calculation problem of the scuffed outline shape. In this study, the author derives the formula for calculating the shape of the hob scuffed profile, and directly calculates the scoop outline shape based on the hob shape calculated by the system. When the formula is derived Using the CNC forming shovel grinding method to grind the hob, the calculated contour data of the sand can be directly used for automatic programming of the CNC forming gear grinding machine, thereby realizing the CAD/CAM integration of the gear hob. Professor Shi Qiaozhang of Kumamoto Institute of Technology, Japan The technology jointly studied by Professor Yoshino Yoshihiro of the Saga University of Japan and one of the authors of this paper has been applied to Japanese gear cutter manufacturers [2].

2 automatic drawing and database processing

After designing and calculating the hob's axial cutting edge and its structural dimensions, the data needed for automatic drawing has been stored in the database and data files. The drawing program segment reads the required data from the database and data files, and after appropriate conversion, Generate screen command integrated drawing files for the AUTOCAD system. This drawing file is actually a text file that brings up all the screen commands for drawing a hob working diagram with the AUTOCAD system and has been sorted by a reasonable process. The system is started directly. AUTOCAD system to automatically execute the file, automatically draw the hob working diagram. Users can directly modify the map as the case may be, and use the printing device (printer or plotter) to print out the engineering drawings.
A major problem in the computer-aided design of hob structural dimensions is the look-up table problem of dealing with a large number of standardized data tables. To solve this problem, you can enter the table into the Foxpro database, through the exchange of data between programs; you can also Forms are processed into subroutines (functions in the C language) and lookup tables are implemented by calling functions [1].

3 HDMES Structure, Function and Features

In the development of expert systems, the following issues are mainly considered: how to combine the calculation method and the reasoning method together to make up for their deficiencies, how to combine the production method and the frame type in the expression of expert knowledge, and determine the design of the inference engine. Directional, reverse, match, inheritance reasoning or other reasoning methods, rational composition of knowledge base, realization of automatic graphics generation function, and realization of a good man-machine interface.
Comprehensive consideration of the above problems can determine the following expert system construction plan: The development of the expert system is based on the development of molecular modules. The sub-modules are divided according to functions and can be divided into hob design calculation sub-modules and shovel grinding wheel design calculation sub-modules. , CAD drawing submodules, CAM interface submodules, consultation and interpretation submodules, and system helper submodules, among which most of the submodules are stored in the system support library, and there is a data exchange relationship among them.
The data flow relationship during use is shown in Figure 2.

Figure 2 functional structure and data flow
Fig.2 Function structure and data flow

When calculating the design of the hob, first use the hob design calculation submodule. The main function of the submodule is to set the parameters stored in the database based on the parameters of the toothed workpiece input by the user from the user interface and the data file. The calculation of the hob knife shape and its structural parameters. The table to be checked in the calculation process is pre-stored in the database in the DBF file format of the Foxpro database. After the calculation is completed, the resulting numerical results are transferred to the graphic library and plotted on request. Stage graphics or automatic drawing.
The calculation of the scoop outline shape is carried out immediately after the design calculation of the hob using the shovel grinding wheel design calculation submodule. The system calls the support library in C language based on the user input parameters and the hob design calculation result. The calculation program is used to carry out the design and calculation of the shovel's frost outline. The data transmission condition is basically the same as that of the hob design calculation process.
The CAD drawing sub-module and CAM interface sub-module mainly realize the CAD/CAM function of the system.
The consultation and interpretation sub-module is implemented using the consulting and interpretation function of the VP_Expert tool [3]. When constructing the knowledge base, some intermediate parameters and results in the reasoning process have been added with comments. The questioning form is: Why is this? Why come to the current conclusion? Etc. During the consultation, the user can select “why” to ask questions from the system in the executive menu under the consultation command. When the consultation is over, if the user feels unsatisfied with the answer to a certain question, he can choose from the consultation command layer. “whatif”, the system will automatically list the menus of the variables to be changed and then quickly respond to the changed consultation results.
The system helper sub-module is a relatively independent sub-module, which provides users with online help during use. This sub-module is based on the Windows 95 operating system, developed with Help Workshop special software, and can be run independently offline. During the use of the system The user can press the F1 key to get dynamic online help if he has operational questions or wants to know about the system. During the operation, some important operation information will appear in the information bar at the bottom of the main window. Prompt information to operate. Of course, users can also get help through menus or toolbars.
In addition, in order to adapt to the current popular requirements for software systems, the system also has some multimedia functions, adding background music, animations and background images to the system. Users can choose and control these multimedia functions according to their own preferences. Change, and the installation of the entire system is also very convenient.
The main features of this system are:
1) Using the VP_Expert expert system development tool to develop the system. Compared with the expert system starting from zero, using the development tools can greatly shorten the construction period of the expert system, reduce the development workload and reduce the development costs. At the same time, VP_Expert has its outstanding The characteristics, especially the ability to generate a knowledge base from the induction table, make the development of the knowledge base extremely convenient.
2) Improved knowledge base construction. The system adopts a combined knowledge representation of production and framework to improve operational efficiency. The representation method is as follows:
RULE n
IF SLOT NAME_1: ASPECT ...
SLOT NAME_2: ASPECT ...
......
SLOT NAME_n: ASPECT ...
THEN
RESULT 1
RESULT 2
......
RESULT n;
3) Build and run in an integrated environment. The system develops the main interface on the Windows platform, consults with the VP_Expert expert system development tool, invokes the computational support library developed in the C language, provides data support with the Foxpro database platform, and finally automates with AUTOCAD. Drawing.
4) Chinese-language consultation and interpretation system. The original consultation and interpretation mechanism of the development tool is based on the English structure. The consultation interface is also based on English. To adapt to the actual needs of domestic users, the consulting and interpretation system has been finished and the consultation has been explained. Appear in Chinese, which is conducive to the promotion and application of the expert system.
5) Versatility. The calculation support library of the expert system contains the design calculation program and uses a universal direct calculation method. It is applicable to arbitrary toothed workpieces such as involute, cycloid, arc tooth and spline. .
6) Strong graphics function. The main stage of the design calculations are accompanied by drawing subroutines, which can give the results of the stage graphics, and can draw out the hob edge and shovel frosting contour according to the requirements. The user can cooperate with the phase calculation results to judge in real time. The correctness of the design, timely detection of errors, return to modify the parameters.

4 system applications

The entire system has been made into the form of an installation disk, as long as the setup.exe installation file in the disk 1 of the operating system installation disk is operated and the operation is performed according to the prompt, the installation of the system can be easily completed [1].
The minimum configuration of hardware and software required for system operation is:
Hardware environment: 486 (66 MHz main frequency) or above microcomputer, 8 MB or more memory, not less than 20 MB hard disk space.
Software environment: Windows95 operating system, AUTOCAD R12 (For Windows) version of the tool software.
The system can perform three types of hob design calculations: Involute hob, Archimedes hob and spline hob. After system startup, the user can select one of the hobs in the pop-up selection window. Press the OK button to start the corresponding design, the next specific operation in accordance with the prompts. Due to the open structure, the system can also be re-developed for other types of hobs, in order to continuously expand system functions.

5 Conclusion

In this study, the author applied the basic principle of space meshing to establish a universal formula for calculating the hob-edge and shovel-sharp contours, and developed a practical hob using CAD/CAM technology and artificial intelligence expert system technology. Design and manufacture of expert systems. Calculation examples show that the results obtained by the expert system can meet the engineering requirements and can be promoted in the production practice of gear cutters.