CAD/CAM software technology and its application in CNC machine tools

Computer Aided Design and Manufacturing (CAD/CAM) technology has been increasingly used in the field of CNC machining. CAD/CAM software technology is also developing rapidly. There are many software products. These products are based on their own development grades and their application. Degree is widely used in different processing occasions, which greatly saves the time period of design and manufacture, and improves the accuracy and speed to a certain extent.

1 CNC machine tools and CAD/CAM

CNC technology is a combination of mechanical processing technology, microelectronics technology, monitoring and detection technology, computer technology, automatic control technology and other disciplines. It is a new and fast-developing high-tech, with the development of electromechanical industry and national economy. Very important role. At the same time, CNC technology is also the basis for the development of automation technology. CNC machine tools and machining centers with CNC technology as the core are representative and high-level mechatronic products, representing the forefront of the development of automation technology in the world today.

The modern CNC system uses an AC digital servo system. The position, speed and current of the servo motor are digitized. As the servo control method, the above-mentioned control theory is adopted, and a high-speed response servo system that is not affected by mechanical load fluctuations is realized. From the development of the world servo system, it has experienced the steps of stepper motor → DC servo motor → motor → AC servo motor.

At present, most CNC machine tools in China are not equipped with special computer-aided manufacturing software, so this topic has a wide range of development space.

CAD (ComputerAided Design), which is a computer-aided design, is a production aid in the process of CNC machining. It has high-speed and accurate computer computing functions, large-capacity storage and processing data, rich and flexible graphics and word processing. The function combines with the designer's creative thinking ability, comprehensive analysis and logical judgment ability to form a system that closely matches the designer's thinking with the computer processing ability, which greatly accelerates the design process. CAD technology includes the following functions: geometric modeling, computational analysis, simulation and experimentation, drawing and technical document survival, management and sharing of engineering databases.

CAM (Computer Aided Manufacturing), that is, computer-aided manufacturing. CAM has a wide range of content. In a narrow sense, it refers to the preparation of numerical control degrees, including the planning of tool paths, the generation of tool position files, tool path simulation and NC code generation.

Computer-aided design and manufacturing combined with CNC machine tool processing is the mainstream of CNC machine tool technology applications, which can achieve very ideal processing results. The NUT series CNC engraving machine produced by the Institute of Motion Control of Nanjing University of Technology uses the control board to connect with the PC, the Windows operation control interface controls the CNC motor; the electrical part uses the Panasonic AC servo system; the CNC machining function: X, Y, Z three-axis linkage , Maximum speed 5000 r / min, encoder pulse output 16 384 p / r, spindle cutting speed up to 15 000 r / min, stepless speed regulation; processing maximum size: 2 400 mm × 2 400 mm × 120 mm, pulse Equivalent: 01001 mm. Using a variety of CAD / CAM software to process the idea through a series of software operations to generate G code, using the execution of the operating software to execute the code and then process the finished product.

The NUT series of CNC machine tools researched and designed by the Institute of Motion Control of Nanjing University of Technology combines engraving machines and various design and processing software. The processing from computer design to manufacturing to machine tools is generally a few steps and modules as shown in the flow of Figure 1.

In this whole process, there are many requirements for software. Except for the electrical operation of the machine tool, almost no computer software can be produced. The software can be roughly divided into the following sections.

(1) Design software

Drawing parts, such as the popular drawing software AutoCAD and UC, PRO/E, 3D in art design software such as 3DMax, Photoshop. This is not limited to CAD software, but also includes a variety of other software that can be used to implement the process.

(2) Manufacturing software

Usually referred to as CAM software, which ultimately generates the processing code. Most manufacturing software also has modeling and mapping capabilities. Divided into two-dimensional, two-dimensional semi- and three-dimensional CAM software according to the occasion of the production application. Such as: CAXA of North Sailing, CAXA manufacturing engineer and MasterCAM, ArtCAM, Cimatron, etc. The manufacturing software generates the standard G code, and then the designed idea is processed on the machine tool, that is, the NC code is sent to the machine tool, and the machine tool is processed according to the instruction, which mainly includes setting the processing environment, setting the machining process, generating the track file, and Post processing, etc.

(3) Execution software

The machine tool performs NC code processing. Its main work is the communication between the computer and the CNC machine tool. It can complete the serial communication of data through the COM interface or realize the parallel communication through LPT. This requires understanding that different vendors apply different wiring and interface protocols to their communication interfaces. But in practice, people often use control boards, so-called machine controllers. These boards are connected to the CNC machine through the data lines, and the interaction between the people is done by the software programs provided by these boards. Now most of the software programs are Windows interface, easy to operate, this article puts these The software is called the execution software, which is the software that directs the machine tool to complete the part processing according to the code instructions. For example, Germany's Editasc, the US PMAC control card and its software products, install the software and load the driver of the motion card in the system, and can also use these drivers for secondary development.

2 File conversion between different software data

There are many design and manufacturing software, and the application scope is different, so the interaction between different software is also a problem that designers must consider. For example, how to input the mold part graphic designed in the CAD software into the CAM software, and then set the tool parameters and tool path according to the requirements, and automatically generate the NC code by using the CAM software; how the three-dimensional model of other non-CAD design software allows the CAM software to recognize Wait.

This problem has been taken into consideration by companies when designing and manufacturing software. Each software has almost the same data conversion interface with other software. These interfaces are reflected in the file format conversion. These softwares support a variety of file formats, so that you can save or export the file to a file format supported by other related software in one software, and then open or import it in the relevant software.

However, this conversion process is also subject to appropriate adjustments depending on the situation. For example: Many CAM software accept dxf files, but CAD entity files converted to CAM in dxf format must be decomposed with CAD entity graphics; 3DMax files need to be modified in sttl format to be converted to MasterCAM because of the conversion process. There may be data loss in it. This requires looking for one of the best conversion formats in two different software.

3 post processing files

The post-processing file is a setting file unique to the CAM software before the NC code is generated. Because there is no specific CAM software for a certain CNC machine, and each CNC machine has different format requirements for the G code, that is, the NC code, it is the post file of the CAM software that plays a decisive role in generating the NC code. Proper adjustments are made so that the entry machine NC code can be identified. Post-processing is actually a text editing process. Its function is to convert the calculated tool path (tool path trajectory) into NC code and output in the specified standard format. This code is then transmitted to the control of the CNC machine through software. On the device, the controller drives the machine tool according to the program statement.

For example, when the NUT series CNC machine is used for electrical test, the G code for executing the software identification is G00, G01, so the CAXA design must be set as follows before generating the G code:

(1) "Application" - "Post Processing" - "Post Processing" in "Post Settings" has a "post file extension: changed to 1nc;

(2) Remove the statements other than G00, G01 in the "post processing setting";

(3) Remove the header and end statements of the generated file;

When generating G code with ArtCAM, all the unnecessary machine tool execution software in ArtCAM's post file Axyz1con is not masked with ";" before the statement is recognized.

To use MasterCAM, change the file with the suffix 1PST in its "post-processing program" form, and modify the file accordingly, and delete the unrecognized statement description, so that it will not be in the generated NC code file. This type of statement appears.

4 CAD/CAM integrated system

With the development of CAD/CAM technology and computer technology, people are no longer satisfied with the independent development of the two, so there is a combination of CAM and CAD, which is to integrate (integrate) the two to adapt to design and manufacturing automation. Requirements, especially the requirements of Computer Integrated Manufacturing Systems (CIMS) that have emerged in recent years. This integrated combination can automatically convert the part information designed and generated in CAD into the input information required by CAM, preventing the loss of information data. Product design, process design and product manufacturing are integrated into one system for increased productivity. Therefore, we have developed a CNC machining CAD/CAM integrated system in CNC machining applications, and the integrated system eliminates the cumbersome data conversion process. The key to CAD/CAM integration is the exchange and sharing of information, such as UGII, Euclid, Pro/E, etc. In the integrated software, the product geometry model is directly obtained from the CAD system in an internal unified data format. Many 3D CAD/CAM software currently provides physical design modules and software packages. We use the solid modeling capabilities of UG and Pro/E, including the geometry, dimensions and technical requirements of the part; then use Pro/E's unique CAM software package to build the tool library and complete the process parameters for the product; The tool path file is translated into G code by the translation file of the software package, and the execution software is entered into the machine tool processing process. The process of integrating software packages and related drivers is done using high-level language VC. The module for the integrated CAD/CAM system is still shown in Figure 1.

5 Conclusion

The development of computers and the development of the software industry have promoted the continuous improvement of computer-aided design software. CAD/CAM technology is developing in the direction of openness, integration, intelligence and standardization. It is more and more widely used in CNC machine tools. The DNC open system based on PC technology has become the development direction of software, and there is nowhere in this network. In the era of impermeability, CAD/CAM technology is also developing in a network. With PC technology, network communication can be easily realized, and the production needs can be efficiently met. For example, in the laboratory of colleges and universities, the network sharing of experimental equipment is extremely urgent. Using the combination of network technology and CAD/CAM technology, the CAD/CAM design—code transmission—machine tool execution—network monitoring and the whole process can be shared. All teachers and students share several or even one CNC machine tool, making full use of equipment, which greatly saves money and time.

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