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In order to improve the level and quality of China's tool manufacturing process, some domestic tool manufacturers and application manufacturers have introduced CNC tool grinding machines from abroad. After a long time of use, these CNC machine tools are basically intact and can still be used. CNC systems have lagged far behind modern CNC system technology and are obsolete. Some domestic manufacturers have developed CNC tool grinding machines, but because of the self-manufacturing of the mainframe and the introduction of the numerical control system, this CNC tool grinding machine is not only costly, but also has no integrated tool grinding technology due to the universal CNC system. Programming software makes it difficult to grind tools (especially complex tools). Therefore, the CNC system of these domestic CNC tool grinding machines must also be modified.
The above-mentioned numerical control system transformation usually adopts the latest special numerical control system of foreign CNC tool grinding machine manufacturers. Although this kind of transformation scheme has the advantages of mature technology, low risk, reliable reliability, and high price, poor programming and other defects. Huazhong 2000 type tool grinding machine special CNC system is an integrated CNC system successfully developed for various rotary tool grinding processes based on the scientific research results of the “Eighth Five-Year†key research project “CNC universal tool grinding machine product developmentâ€. . With this system, the above problems can be solved well, and the cost is still low.
2 Functions and structure of the CNC system after the transformation 2.1 Basic functions of the system After the tool grinding machine is modified by the Huazhong 2000 tool grinding machine numerical control system, the system has the following three basic functions.
The universal CNC system function system retains the basic functions of the original general-purpose CNC system, such as the axis control function of up to 16-axis CNC 9-axis linkage, program verification function, MDI function, linear, arc, and spiral interpolation functions, M, S , T function, fault diagnosis display function, embedded PLC function, etc.
Automatic NC programming function The biggest feature of this system is that it integrates the tool grinding programming software on the basis of the standard universal CNC system, and directly inputs the structural size and processing technology of the tool to be polished in the graphical menu mode on the CNC system. Automatic programming and processing to achieve integration of programming and processing.
Tool measurement and automatic tool setting function In this system, the tool measurement function is integrated in the CNC system. In the CNC grinding of the tool, the automatic tool setting solves the problem of cumbersome manual tooling and poor precision.
2.2 System hardware structure The hardware structure of the modified CNC system is shown in Figure 1. It consists of three parts: computer numerical control unit, servo drive unit (including motor) and measurement unit.
The numerical control unit includes an industrial PC, a position control module, an input and output module, and is the most basic unit that constitutes a numerical control system. The industrial PC can be configured with CPU, memory, display card, display, hard disk or electronic disk, floppy disk drive, etc. as needed; the position control module has multiple position detection interfaces, and collects the pulse signal of the photoelectric encoder as the position feedback of each coordinate of the machine tool. And control the speed unit through multi-channel D/A output signal, which can be matched with the all-digital AC servo unit and motor produced by Wuhan Huazhong CNC Co., Ltd., or with Siemens AG, AMK, Sanyo, and Matsushita of Germany. The drive unit is matched. The input and output module is the hardware input and output interface of the PLC embedded in the CNC system. The input and output voltage is 24V, and the maximum current is 100mA. It is used for the button signal input of the operation panel, the switch detection input of the machine tool, etc. The basic input/output points are 48/. 48 points can also be expanded to 256/196 points as needed.
The servo unit and motor are the most important guarantee for the reliable operation of the system. The AC servo unit uses a photoelectric encoder to achieve position detection feedback, 2500 pulses / r. The minimum resolution of the system is 0.001mm / 0.001 °.
The measuring unit is the necessary hardware component for the system to implement tool measurement and automatic tool setting. Includes signal processing modules and measuring components. The former mainly refers to A/D conversion and data filtering, the latter is tool measurement and tool setting sensor (probe), and contact or non-contact probe can be selected according to needs.
2.3 System software structure 2.3.1 Overall structure Huazhong I general-purpose CNC system is based on DOS development and adopts layered modular structure. The system software is divided into four layers: the first layer is the operating system layer, including file management, process management, real-time task scheduling, and the physical management layer of the parameter database. The system management software is expanded on the basis of DOS, adding real-time task scheduling, CRT driver, and parameter library interface software. The entry to the task control is INT62, soft interrupt, with control primitives for scheduling, creating, suspending, undoing, blocking, waking up, delaying, and getting the status of the task. The second layer is the input and output layer of the machine tool, including position loop control software, MST code output, adjustment management and digital input and output. The position control software receives control and position commands through the internal communication area and passes the position control commands to the servo unit. The third layer is the interpolation control layer, which is interpolated by ISO code, including interpolation, tool compensation and program compilation. The fourth layer is the user operation layer. The specific content of each layer is shown in Figure 2. This hierarchical modular structure is easy to improve and transplant. Tool NC grinding automatic programming software and tool measurement and automatic tool setting software are integrated in the user operation layer.
2.3.2 Tool CNC grinding automatic programming software [2]
The structure of the tool NC grinding automatic programming software is shown in Figure 3. The software is mainly composed of the following parts:
(1) The process database programming software collects the relevant process data of the tool to be programmed, organizes and manages it with a suitable data structure, and forms a process database. These process data include numerical control system information, machine structure information, tool geometry parameters, grinding wheel shape parameters, machining process information, and machining process parameters. The process database is the support of the entire programming software. The numerical control system information is the information describing the numerical control code format of the numerical control system used, and is the information necessary for the format conversion in the post processing; the machine structure information is used to describe the structural model and structural parameters of the numerical control tool grinding machine, including the machine tool model code, The initial positional relationship between the coordinate axes of the machine tool kinematic chain and the direction of the motion axes of the machine tool [2]; the tool geometry parameters refer to the structural parameters and cutting parameters of the tool being machined, and the tool structure elements are used as the basic objects; the shape parameters of the grinding wheel are The parameters used to describe the shape and size of the grinding wheel; the machining process information is used to describe the machining process of the programmed machining tool. The system classifies, organizes and grinds the grinding process of various tools with the basic components of the tool structure. Management, forming a processing operation library; processing technology parameters mainly refer to the feed speed, main cutting speed, feed amount, machining allowance, coolant switch and other information in the various processing steps of the tool.
(2) Parameterized input module The parameterized input module is an interface for programming software to realize human-machine information interaction. The module transfers the relevant process parameters from the process database by inputting the processing information, and then makes necessary modifications to the process information according to the specific processing object, processing conditions and processing requirements, and generates a module for subsequent tool position calculation and tool position verification. The data file used by the post processing module. Specifically: CNC system settings, machine settings, tool settings, process settings, grinding wheel settings, process settings.
(3) Programming library and tool position calculation and tool position verification module The programming program library is the program of the tool position calculation program and the tool position verification program for all programming tools of the programming software. The function of the tool position calculation and the tool position verification module is to sequentially read out the machining element information of each machining process, the grinding wheel cutting surface information and the process information from the machining process file, and call the corresponding tool position from the programming library according to the information. Calculation program and tool position verification, generating tool location data files and CC point data files. Tool position calculation and tool position verification are the key to automatic programming. The programming library is the core of the entire programming software.
(4) Post-processing The post-processing is the process of converting the tool position file generated after the tool position calculation into a numerical control code that can be executed by the CNC tool grinder. Including machine tool motion solving, nonlinear machining error checking and processing, feed rate checking and correction, and file format conversion.
2.3.3 Tool Measurement and Automatic Tool Alignment Software This software consists of two relatively independent software modules for tool measurement and automatic tool setting, both based on a common hardware structure. The function of the tool setting software is to determine the relative positional relationship between the programmed coordinate system and the machine coordinate system. As long as the hardware is reliable, the software is relatively simple to implement.
For regrind machining of tools, since the theoretical data on tool shape and cutting parameters are not known, the only basis for NC programming and machining is the tool physical model. The function of the tool measurement system is to convert the geometric analog quantity of the tool physical model into the geometric digital quantity that the automatic programming software can receive by sampling the physical model of the tool to realize tool programming and processing. The tool measurement software is mainly composed of the probe motion control module, the data acquisition module and the data processing module. The probe motion control module is the key of the whole software. It has different types for different tool types and processing requirements and different probe types. Motion control strategy (limited to space, this article will not be expanded).
3 Numerical control system transformation example Figure 4 shows the Helitronic 30 NC numerical control tool grinding machine produced by WALTER Company imported from Germany by an aircraft manufacturer in China. The grinding machine has 5 machine axes (X, Y, Z, A, B). 3 axes (X, Z, A) can be realized for the two axes (X, A) linkage, and the other two axes (Y, B) are manual axes. The tool grinding machine is actually a manual/automatic dual-purpose machine tool. The manual operation mode can complete the simple function of internal and external grinding. In the automatic machining mode, the system has three automatic machining programs, which are: 1 external grinding program; 2 spur cylindrical cutter indexing grinding program; 3 helical cylindrical cutter (indexing) grinding program.
Prior to the transformation, the tool grinder mainly had the following defects and problems: 1 The machine tool operation and control were completely carried out through the buttons on the panel, which was quite cumbersome and complicated; 2 could not realize the three-axis linkage; 3 can only be automatically processed according to the inherent three procedures. , can not be programmed separately; 4 CNC system aging, can not run stably. Therefore, the grinding machine must be modified.
According to the aforementioned technical transformation route and technical scheme of the machine tool, the numerical control system of the tool grinding machine was transformed. The main changes include:
(1) The hardware transformation replaces the original control system hardware with the Huazhong 2000 CNC unit; replaces the original X, Z, A axis stepper motor and drive unit with the Japanese Panasonic AC servo unit and motor; adds tool measurement and tool setting device; The spindle unit and hydraulic system of the original machine are retained.
(2) Software transformation Replace the original control system with the special CNC system of Huazhong 2000 tool grinder.
After the tool grinding machine is modified by the numerical control system, the functions and technical features are as follows: the machine tool can realize the linkage of three axes (X, Z, A); the flank grinding of various milling cutters can be performed; directly on the CNC with graphical menu mode Input the parameters and processing technology of the tool to be processed or grinded, and realize the integration of programming and processing; with the tool geometry measurement function to ensure the re-grinding of the knives of various milling cutters; Tool parameters, grinding process and grinding amount can be easily modified to give full play to the operator's rich experience. The tool grinding and grinding process is very convenient; the machine tool movement is controlled by computer, realizing the program control in the true sense. Make operation simple and reliable.
After the machine tool was modified by the numerical control system, the system operation evaluation and machining experiment were carried out, and the flank surface grinding of the cylindrical/conical end mill and the ball end milling cutter was successfully realized. 
1 Introduction CNC tool grinding machines, especially multi-axis CNC and multi-axis CNC tool grinding machines are high-quality, high-quality grinding tools for manufacturing high-precision and complex-shaped tools with high-precision and complex shapes. Mechatronics high-tech products with high degree of automation, high precision and reliability require considerable technical difficulty in research and development. Grinding of tools by CNC tool grinding machines must rely on tool grinding technology and programming technology, and the grinding technology and programming software of various complex shape tools are currently patented or confidential in foreign countries. Because of this, there are only a few manufacturers in the world that can produce high-performance CNC tool grinding machines.