Abstract The software and hardware structure of CNC flame cutting machine CNC system developed with industrial personal computer (IPC) are introduced. The CNC system not only has the control function suitable for the technological characteristics of the CNC flame cutting machine, but also has the functions of graphic programming, profiling programming, screen simulation and real-time multi-task processing, and the interpolation method uses differential interpolation. Can directly perform interpolation on all quadratic curves.
Keywords: IPC flame cutting machine CNC system graphic programming dynamic simulation differential interpolation multitasking
I. Introduction
At present, the domestic CNC flame cutting machine CNC system, the main host used is a single board machine, microcontroller and DOS platform 386CPU the following grade PC, the operating system there is a problem of low performance and functionality, it is inconvenient to use. Therefore, it is necessary to develop a CNC system with good performance, complete functions, and convenient programming and operation. First, the old CNC flame cutting machine control system is updated, and the second is the support for the new CNC flame cutting machine. With the improvement of the performance of IPC machines and the reduction of prices, the great advantages of developing CNC systems with IPC machines have gradually emerged. In addition to higher reliability and anti-jamming capability, IPC machines have the same high speed and rich hardware resources as PCs (CPUs, memories, coprocessors, hardware and software drivers, serial/parallel ports, interrupts, timings). Devices, bus slots, monitors, keyboards, power supplies, etc.), software resources (Windows platforms and various development software that can be used, such as AutoCAD, network communication, etc.) and function calls, with an open architecture and high The cost performance ratio. As long as the drive system servo control card and I/O card that are self-developed or purchased from the market are inserted into the bus expansion slot, the IPC machine can be developed on the basis of fully exploiting and utilizing the inherent functions of the IPC machine and developing its own control system software. Become a CNC system that can perform real-time multitasking, friendly interface, and powerful functions. Moreover, with the constant upgrading of IPC machines, the CNC systems developed with them are also easy to update. This article describes the numerical control flame cutting machine CNC system developed by the IPC machine as a hardware platform and Windows as a software platform.
Second, the hardware composition of CNC flame cutting machine CNC system
The mechanical part of the CNC flame cutting machine is mainly composed of a base, a gantry type moving frame, a flame nozzle, a transmission mechanism, and three stepping motors (not shown) to realize the cutting and processing of flat plate parts. Three stepping motors control the front and back movement of the gantry frame (Y motor), the left and right (X motor) and the vertical movement (Z motor) of the flame spray head, and the X, Y, and Z axes can realize linkage control. The hardware structure of the numerical control system is shown in Fig. 1. The control system uses IPC (486 or more CPUs, 8MB or more, 500MB or more hard disks) as the host. In addition to the IPC's inherent hardware (CPU motherboards, TVGA cards, and power supplies), only a 32-bit optical isolation I/O is added to the slot. O.TIMER (Parallel input/output/timer) card. The I/O parallel port of the card controls the operation of three stepping motors, acetylene switch, acetylene ignition, cutting oxygen switch, and the limit travel switch signal and coordinate zero signal of the receiving workbench. The 8253 timer on the board is used as the interrupt timer of the stepper motor operation interrupt service routine, and the clock frequency is taken as 2 MHz. Through the computer's keyboard to achieve the control system. The pulse equivalent of the three moving direction stepping motors is 0.01mm. Due to the high running speed of 486 or higher PCs, it is completely possible to use a single CPU to complete all the work from system program management to process control. There is no need to adopt multi-CPU architecture for upper and lower machines.
Figure 1 CNC system hardware structure
Third, CNC flame cutting machine CNC system software structure
1. Software composition The CNC system not only includes all the functions of an ordinary CNC system, but also has the functions of automatic ignition, preheating, cutting oxygen, end-of-process flameout before cutting, and rapid retreat and advancement of the cutting torch by machining trajectory during machining. Suitable for its process features. In addition, the system software also has sophisticated graphics programming, profiling programming, direct interpolation of various conic curves, dynamic tracing of machining trajectories, dynamic simulation of machining trajectories, fault diagnosis, communication of processing programs, and other functions. . Among these functions, the rapid retraction and advancement of the torch by the machining trajectory is to increase the imperfection of the individual parts of the steel plate that occur from time to time in the machining process. When this phenomenon occurs, just press the quick return key, the torch will quickly move back to the original track. When it reaches the starting point of the uncut point, the key will be lifted and the torch will be resumed along the original track. Cutting. Figure 2 shows the modular structure of the CNC system software. Because the system software is developed under the Windows interface, it has all the advantages of the Windows program: Breakthrough 64kB memory limit, you can run multiple applications (real-time multi-tasking), convenient keyboard and mouse window operations.
Figure 2 The flame cutting machine CNC system software module structure
2. Programming Method The system software provides three programming methods: graphic programming, profiling programming, and manual programming. Manual programming is only one function module in graphic programming and profiling programming, ie full-screen program editing, so there is no single column in the software block diagram.
1) Graphical Programming The system's graphic programming module is developed on the basis of AutoCAD R12.0. Apart from having all the functions of AutoCAD R12.0, it mainly adds two functions: (1) Automatic programming function - will use AutoCAD The generated graphics file is used for information extraction and path optimization of the processing trajectory (line, circle, circular arc, ellipse, and fold line) (the purpose is to reduce the idle stroke) and is converted into a corresponding machining program, and can be connected before and after the processing trajectory. Add empty run commands between the curves. Here, in order to make the processing path more in line with the requirements of the processing technology, some or all of the paths can be selected by human-computer interaction; (2) Real-time simulation function—interpolation operation and dynamic graphic display using the obtained machining program. If the machining program is correct, the machining trajectory should gradually cover the drawing drawn by AutoCAD with a thick line of another color, and the empty running track can also be displayed with a specific color line. With this programming, the operator can easily check whether the machining program and the machining path are correct, whether it meets the requirements of the machining process, and make timely modifications.
AutoCAD has a powerful drawing function. Through the development of AutoCAD, it has become a powerful programmer of the CNC flame cutting machine CNC system, making it a major feature of the CNC system.
2) Profiling Programming For a workpiece that is not dimensioned but has a contour pattern, it can be programmed using profiling. The programming process of the program is: (1) scanning the contour pattern with a scanner and forming a binary image file, a small contour pattern can be input in one scan, a large contour pattern can be divided into multiple scan inputs, and then in the image editing Splicing on the software; (2) smooth noise reduction, while repairing the broken line; (3) refine processing to obtain the outline image; (4) vectorization according to the given accuracy, and generate DXF graphics files. After the graphics file is formed, the graphical programming CAD software developed above can be used for editing and programming.
3. Fast graphic display and dynamic simulation of the machining program The fast graphic display of the machining program has two functions: one is the preview of the machining track graph, which allows the operator to find the program to be selected from numerous machining programs; Shows the size and position of the machining track pattern relative to the table, and displays the two largest machining sizes in the X and Y directions at the same time. This allows the operator to intuitively understand the size of the machining and the operating range of the machining. The machining program quick graphic display shows only the machining path and does not show the empty path.
The dynamic analog simulation function also has two functions: one is to check the processing program for syntax errors, the other is to check whether the processing path is correct and reasonable, and whether it meets the requirements of the processing technology. Dynamic simulation not only displays the processed trajectory, but also displays the trajectory of the air run (different colors). At the same time, it also accompanies the coordinate reversal display. In the process of dynamic simulation, the operator can pause, continue and single segment exactly like the actual operation. Operation and other control, speed can also be adjusted at any time, you can get more comprehensive information processing, determine the correctness and rationality of the processing program.
If the processing program does not meet the requirements of the processing technology, the system software has the function of converting the processing program into the AutoCAD DXF format file, so that it can be re-edited by returning to the AutoCAD state. When machining programs are converted into DXF format files of AutoCAD, the machining track and air running track are processed with different layers and different colors. This function provides extremely favorable conditions for the modification of the machining program.
4. Other machining operation control programs adopt the common front and back program structure. Among them, the background program is responsible for controlling the initialization of the port, interpreting and preprocessing the processing program, suspending the program operation process, continuing, single-stage stopping, ignition, preheating, controlling the cutting oxygen, extinguishing the flame, adjusting the speed, and processing track dynamic tracking. The display and coordinate values ​​are dynamically flipped and displayed. The torch quickly returns to the running track and progresses forward. The foreground interrupt service routine is responsible for the modification of the timer interrupt time constant, the interpolation operation, and the output of the stepper motor control signal.
Fourth, the conclusion
The rapid retreat and advance function in the machining process makes the control system more suitable for the process characteristics of flame cutting; graphics programming, profiling programming, dynamic simulation and other functions, brings about the preparation and inspection of CNC flame cutting machine processing program. Great convenience; the human-computer interaction interface for Chinese characters increases the operability of the system; real-time multitasking enables the CNC system to perform other processing tasks while performing process control; new interpolation The adoption of the method enables the system to perform direct interpolation for quadratic parabolas, ellipses, and hyperbolas. This enhances the system's interpolation calculation function and reduces the difficulty of programming such curves. In short, the successful development of this system has taken a step forward in improving the grade of the domestic CNC flame cutting machine control system.
In addition, the control system has a certain degree of versatility, in addition to the use of CNC flame cutting machine, only a small amount of modification, can be used as water jet cutting, laser cutting and other machine control systems.
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