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Research on NC Embedded PC Open CNC System

Posted by: Fymicohuang 2021-07-29 Leave a comment

At present, various advanced manufacturing technologies have been developed rapidly, and most of them need the support of numerical control technology. However, since traditional numerical control systems are almost closed, and most machine tool manufacturers choose standard numerical control devices to configure machine tools, which brings difficulties to flexibly configuring the functions and user interfaces of numerical control devices under different usage conditions. Because the standard control device cannot reflect the experience of the machine tool manufacturer, it is also difficult to meet the special requirements of the end user. Therefore, new requirements are put forward for the numerical control system. At the same time, with the diversification of user needs, the production method is developing in the direction of small and medium batches, requiring the CNC system to be more flexible, flexible and versatile. Therefore, research on the structure of the open CNC system has emerged. Many countries in the world have invested a lot of manpower, material and financial resources to research it, and have achieved great results. For example, the open CNC system has software openness and hardware openness, which allows people to choose CNC freely. Devices, servo amplifiers, sensors, execution units and other components. Generally speaking, an open CNC system should have the following characteristics: It is composed of various logically independent constituent elements.

Provide a standard and specification to ensure that the constituent elements of different manufacturers that conform to the specification can form a complete CNC system.

The topological structure of the CNC system can be changed dynamically.

Interoperability with other systems or software modules.

Provide a good and consistent human-machine interface.

Due to the rapid development of computer technology and its standardization and openness, an open PC-based CNC system appeared. At the same time, the CNC system is very popular due to its high performance/price ratio and strong market competitiveness.

1 PC-based open numerical control system PC-based open numerical control system can make full use of the computer’s software and hardware resources, can use general high-level language to easily compile programs, and users can easily combine standardized peripherals and application software and use. The use of a computer is also convenient for networking. PC-based open CNC systems can be roughly divided into four types, namely PC-connected CNC, PC-embedded CNC, NC-embedded PC (NC-embedded in PC), and full-software NC. PC-connected CNC: this type of system It is composed by connecting the existing prototype CNC and PC with a universal serial line. The system is easy to implement, and the prototype CNC can be used almost without modification. General-purpose software can also be used, but the prototype CNC cannot be open, and the communication and response speed of the system is slow.

PC-embedded CNC: This type of system loads the PC into the CNC, and the PC and the CNC are connected by a dedicated bus. The system has fast data transmission and rapid response. At the same time, the prototype CNC system can be used without modification, but the general-purpose PC cannot be used directly, and the openness is limited.

NC embedded PC (NC embedded PC type): This type of system is composed of a special CNC card inserted into the expansion slot of a general-purpose PC.

It can fully guarantee the system performance, the software has strong versatility, and the programming process is flexible. However, the prototype CNC resources are difficult to use.

Full software NC: This type of system means that all the functions of CNC are processed by the PC, and the servo drive is controlled through the servo interface card installed in the expansion slot of the PC. The software has good versatility and flexible programming processing. However, the realization of real-time processing is more difficult, and it is more difficult to ensure the performance of the system, and the prototype CNC resources are difficult to use.

2NC embedded PC type open CNC system 21NC embedded PC type open CNC system application platform As a PC-based open CNC system, NC embedded PC type open CNC system application platform can be understood as consisting of an open motion control card + PC machine . The open motion control card generally uses high-speed DSP as the CPU, has powerful motion control and logic control capabilities, and provides a set of CNC core APIs for users to develop and build the required CNC system. PCs usually use industrial computers, which can make full use of their rich software and hardware resources. Users can choose many popular programming software, such as DELPHI, VISUALC++, C++BUILDER, etc. This can greatly improve the CNC system’s user interface, graphic display, dynamic simulation and network communication functions. The typical structure of the application platform of NC embedded PC open CNC system is given.

System K sets I and applies i to the factory numerical control kernel AH communication system 丨 operating system hardware industrial computer 1 open motion controller NC embedded in the typical structure of the PC type open numerical control system application platform 22 NC and PC communication problems can be seen from this, in When developing an application on this CNC system platform, the first thing that must be solved is the communication problem between the NC and the PC. In other words, the NC and PC should be able to exchange data smoothly. The communication between them can be realized by different communication mechanisms, the typical ways are: bus communication and dual-port RAM communication, etc. The bus communication adopts the ISA/PCI bus structure, the open motion control card is inserted into the bus interface slot of the PC, and the corresponding control register and protocol are used to establish the communication between the PC and the NC, which can use query mode or interrupt mode . Dual-port RAM communication uses a special memory. The memory has two ports that can be connected to the PC and the CPU of the NC. The two CPUs can read and write without interfering with each other. This communication method is adopted. Can significantly improve the speed of data exchange.

In order to make the communication system independent of the specific communication mechanism, abstract the above-mentioned communication methods and obtain a consistent application program interface.

to ensure that users only need to access the application program interface without having to care about the underlying communication mechanism to establish the required communication. Describes the communication system.

The application software is compiled using COM component technology. COM components are actually some small binary executable programs that can provide services for applications, system programs, and other COM components. The COM component objects can be accessed through the standard COM component interface and connected to each other to form a complete application.

Using the COM component architecture application has a series of advantages: the customization of the application, by replacing the COM component object with the same COM component interface, realizes different application functions.

The rapid architecture of the application program, select the required components from the component library, and quickly assemble the application programs required by the architecture, shortening the application development cycle.

The dynamic architecture of the application program, you can dynamically remove or replace the corresponding components without recompiling, and dynamically change the application program function.

It can be seen that the COM component technology is very suitable for the development of open CNC application systems.

The modules are divided according to the different functions of the CNC system, such as logic control, motion control, dynamic simulation, human-machine interface and other modules. Then use the COM component technology and the corresponding CNC kernel API to package these modules, so that each module has a unified COM component interface, so that the CNC application modules of different suppliers can be exchanged. Make user customization possible.

24 system configuration software combines scattered various COM components into a numerical control application system that meets user requirements and is implemented by system configuration software. The system configuration software can instantiate the COM components in the COM component library according to the user’s choice, connect and combine them, and assemble them into an application system with specific functions. When the user’s needs change, the corresponding COM components can be replaced through the system configuration software or some COM components with required functions can be added to adapt to the changes in demand.

3 Case Study This paper develops a man-machine interface-operation panel with NC embedded in the PC-type open numerical control application system. The application platform of this example uses the open motion control card MWIPMAC of DELTATAU of the United States. MWI-PMAC can control two axes at the same time and has strong motion control and logic control capabilities. It is inserted in the ISA bus interface slot of the microcomputer. The system also uses two fully digital AC servo drives (MR-2) and AC servo motors. In addition, a numerical control interface chassis is equipped with I/O interface and analog output/feedback interface terminal board inside. The operating system on the microcomputer is Wiodows95, and DELPHI is used as the development language. The structure of the entire platform system is as shown.

The man-machine interface application system developed by the operation panel application system platform structure block diagram provides the user with an operation interface, and the user completes the corresponding operation by clicking the mouse. The realized functional modules include programming, automatic processing, manual operation and motion trajectory description. The overall framework of the application system is as shown.

I Programming automatic processing I丨Manual operation丨I trajectory description I The overall framework of the operation panel user interface application system 3.1 Communication module The communication module is a necessary module for information interaction between the microcomputer and the PMAC motion control card. It realizes the query-based method The bus communication and dual-port RAM communication. Here we discuss the dual-port RAM communication more specifically. There is a dual-port RAM on the PMAC motion control card. The microcomputer and the PMAC motion control card can share this dual-port RAM. In order to use the dual-port RAM, a 16K unoccupied storage space is selected on the microcomputer, and the storage space is The starting address is set as the starting address of the dual-port RAM on the microcomputer. Then write the segment address of the starting address to the memory with address values ​​of 786 and 787 in the X storage space of the PMAC motion control card, and the PMAC motion control card can use these two memories to determine the address of the dual-port RAM, thereby achieving Dual-port RAM communication.

3.2 Programming module The programming module provides users with a graphical interface, which allows users to compile CNC programs conveniently and quickly. It mainly has the functions of inserting, deleting and modifying CNC programs.

3.3 Manual operation module The manual operation module realizes functions such as zero return and incremental feed, and their realization is mainly through the use of online commands of PMAC. The corresponding online command is sent to PMAC through bus communication, and PMAC receives the command and executes it.

3.4 Automatic processing module The realization of the automatic processing module is relatively simple by starting the motion program stored on the PMAC board. But the position and speed of the motion axis must be collected in real time and displayed.

3.4 Trajectory drawing module The tool trajectory drawing function is realized by using the powerful logic control ability of PMAC, running the PLC program on the PMAC board, reading the current tool position information in real time, and then dynamically drawing the tool position information with a curve So that the changing process of the tool path can be visually observed on the screen. The tool path is drawn using a control PAINTBOX of DELPHI. When the motion program runs 0 inch, PMAC has a PLC program to read the current position information and store the information in the dual-port RAM. The microcomputer reads the dual-port RAM through the TIMER control to obtain After the above-mentioned position information, draw the pixel points of the current position of the tool on the PAINTBOX control, thus realizing the dynamic depiction of the tool path.

is the window of the man-machine interface application system.

(Next to page 37) The entity model diagram of the plug-in and the plug-in is obtained through Boolean operation, and then the calculated intersecting lines are drawn in different colors on this theoretical reference object, and the calculated results are well verified by comparison Whether the intersecting line is consistent with the intersecting line in the solid model, that is, the correctness of the digital model is verified, see the intersecting line verification. 3NC command generation The function of the NC command generation module is to generate the corresponding cnc machine tool’s CNC command and its machine tool adjustment file. The machine tool adjustment file contains pipe design parameters, blanking dimensions, process parameters that need to be adjusted during processing, and tool setting positions. After the file is printed out, it is used by the CNC operator, and the CNC instruction file is transmitted to the CNC machine tool by floppy disk or RS232C communication. This system generates four data files at a time: plug-in NC program file and machine tool adjustment file, plug-in NC program file and machine tool adjustment file.

3.4 Machining simulation Machining simulation is realized by reverse simulation, that is, by reading the CNC program and machine tool adjustment file generated in the previous step. The machining simulation effectively verifies the future machining process and ensures the correct machining of the workpiece. The idea of ​​the system’s processing simulation is to simulate the mechanism of the experimental cutting process, and realize all the pipe cutting processes (flame, plasma arc, laser) in the processing. The essence is to form holes first, and the machine tool moves according to the specified trajectory to make the holes continuous and form very narrow Cut seams. Machining simulation is carried out using this point. First read the CNC program file and the machine tool adjustment file, automatically draw the cutting head and pipe fittings, and then let the cutting head automatically enter the tool setting point according to the tool setting position and size, and then control the MDT command at the tool setting point to make a mark on the pipe. The hole (hole) is read through the program cycle again, and the instruction data is obtained to rotate the pipe, and the cutting head moves AX, AZ to the next cutting point, and then punches another hole, and so on. Because the step distance is small, and there is no interpolation movement and continuous cutting is formed, the entire simulation processing process is completed.

In order to show this process, a processing simulation process diagram when the step distance is large is drawn.

4 Concluding remarks The key to the CNC cutting of the pipe intersecting line is to establish a mathematical model of the CNC cutting intersecting line corresponding to the principle of CNC cutting. Based on the actual situation of the factory, this paper provides a complete solution for the Cnc Machining of pipe intersecting lines. The graphical interactive automatic programming system developed allows programmers to get rid of complex mathematical processing. The system is intuitive and clear, vivid, easy to use, simple to operate, etc., which greatly facilitates programmers and operators, and has strong practical value and promotion value. In addition, the slightly improved algorithm in this paper is also applicable to the generation of CAD for tube sheet metal unfolding and NC cutting programs for unfolded parts.

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