Research on CAM integration technology in the hott

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Research on CAM integration technology in virtual manufacturing environment

the market in the 21st century will move towards globalization, the business environment of enterprises will continue to change and unpredictable, and the product demand will be more personalized. Therefore, the future market competition puts forward higher requirements for enterprises. Agile manufacturing is a new production mode that adapts to this form and faces the 21st century. Virtual manufacturing is a means and method to realize agile manufacturing. Based on modern computer network technology and information technology, it comprehensively uses simulation, modeling, virtual reality and other technologies to model the whole production process and manufacturing environment of design and manufacturing on the computer, so as to realize the whole process simulation and simulation from product conceptual design to final realization. CIMS is the foundation of agile manufacturing. As the key technology of CIMS and virtual manufacturing, cad/capp/cam/mps (machining process simulation) integration technology is the basis of implementing agile manufacturing. Therefore, the research on cad/capp/cam/mps cell technology is of great significance to the full implementation of agile manufacturing in the future

cad and CAM technology has gradually stepped into maturity and commercialization, and computer simulation technology is more and more used in the manufacturing industry. Because of its diversity and complexity, CAPP has not been able to keep up with the development of CAD and cam, so it also restricts the development of cad/capp/cam/mps integration technology

when many existing cad/capp/cam integrated systems automatically generate NC codes, they rely on dividing the machined parts into the most basic machining unit features, design a fixed NC program library for each machining step of each machining feature, and generate NC programs for machining specific parts according to the sequencing results of machining steps, tool selection, and cutting parameter selection of CAPP. The advantage of this method is that the integration method is simple, but its NC program library is for a specific NC system, so it is not flexible. In addition, it cannot be effectively integrated with machining process simulation. It is not in line with the development trend of highly flexible and integrated manufacturing system in the future

As a new generation of automatic design software, pro/e is widely used in industry. It integrates design and machining process and NC code generation under a unified platform, and has strong design and machining functions. However, due to the lack of information integration with CAPP, the information integration of cad/capp/cam/mps is cut off. A large amount of machining information generated by CAPP cannot be used by cam. Moreover, the machining simulation function of the existing cad/cam software is too simple, and many special simulation software have no mature interface with these cad/cam software, which can not meet the needs of virtual manufacturing

therefore, how to automatically complete the machining process by extracting the automatic planning results of CAPP, using the machining function of pro/e, and providing MPs with the information required for machining process simulation, so as to realize the information integration and function integration from CAPP to cam and MPs is the focus of this paper

1. Overall system structure

cad/capp/cam/mps integrated system architecture is shown in Figure 1. The whole system integration is based on the step standard. For non rotating parts, CAD uses pro/e to complete the part modeling and extract the part processing feature information, and then outputs it to CAPP in the format of step neutral file. CAPP automatically completes the process planning. After cam reads the process planning results, cam uses the processing function of pro/e to automatically complete the machining process simulation on the computer, and then outputs the tool position file, Tool position simulation completes the material removal inspection of tool position drive. Cam-post (cam post processing) completes the conversion from tool position file to NC code when there is abnormal or bearing temperature rise is too high. NC code simulator completes virtual machining driven by NC code on the basis of establishing machining equipment model, part model, blank model, fixture model and tool model. Check the collision interference and NC code errors in the processing process, and put forward suggestions for modification

Figure 1 system structure diagram

2. Cam function integration

unlike many other cad/capp/cam integration systems, the cam of this system makes full use of the processing function of pro/e, a mature commercial cad/cam software. But at the same time, the secondary development of pro/e avoids a lot of human-computer interaction when directly using pro/e processing function. The system function integration is shown in Figure 2. In pro/e environment, to complete a machining step of a feature manually, it is necessary to choose a machining method interactively, specify machining features and various feature geometric parameters related to this machining feature, and fill in tool parameter table, cutting parameter table, etc. Therefore, it is actually equivalent to completing the work of a process planner. This requires that the user is an experienced craftsman and a proficient pro/e user, who has high requirements for users and heavy workload

Figure 2 system function integration diagram

the cam of this system has carried out a new design and development for the acquisition of pro/e processing information, and CAPP completes the processing process sequencing, processing tool selection, and cutting parameter selection. Cam reads the result of CAPP and writes it into a menu click file format that can be recognized by pro/e. This menu click file is automatically run in pro/e to automatically complete the simulation of the part processing process and generate the tool position file. Therefore, it saves a lot of manual interaction time and reduces the requirements for operators, and completes the effective integration with CAD and CAPP at the same time. The generated tool position file can be used for tool position driven blank material cutting simulation, so that cam can be effectively integrated with simulation. The tool position file is also input to the cam-post processor to complete the post-processing. The post processor generates the appropriate NC code according to the specific NC system, avoiding the disadvantage of poor flexibility in generating NC code by using the NC subroutine library in the past. Cam-po is about fighting. "The NC code generated by st is expected to double the output value of Wanhua Ningbo Industrial Park on the existing basis as the input of NC code simulator. The simulator models the actual machining equipment, constructs the spindle head and working platform model of the machining center, and reads the machining model and tool information provided by cam, which is composed of parts, blanks and fixtures. A virtual machining environment that is completely consistent with the actual physical environment is established in the computer to complete the simulation of the machining process, which greatly reduces the time and cost of trial cutting

3. CAM information integration

compared with the previous cad/capp/cam/mps integrated system, this cam system has some special requirements for machining part information and process information. When processing a part in pro/e environment, it is necessary to establish a processing model (.Mfg file) first. The processing model is shown in Figure 3, which is composed of part model, blank model and fixture model. Part model, blank model and fixture model are completed by part CAD, blank CAD and Fixture CAD respectively. Because pro/e has the characteristics of unified database and full correlation, any changes in CAD will be truthfully reflected in the processing model, ensuring the completeness and unity of information. On the basis of part information, blank information and fixture information, all process information of machining is provided by CAPP module to ensure the rationality of information flow. Due to the special requirements of pro/e machining, the CAPP of this system is different from the traditional CAPP system. CAPP provides the sorting result of feature machining, tool parameter description file, cutting parameter description file and machining feature description file. The tool parameter description file and cutting parameter description file should meet the requirements of pro/e, so that the left side of the pendulum above the pendulum coincides with the calibrated scribed line. It not only describes the tool parameters and cutting parameters provided by the ordinary CAPP system, such as tool type, tool length, tool diameter, cutting speed, feed speed, etc. It also provides some more specific and perfect processing parameters, such as controlling the number of cutting paths, the direction of cutting paths and the height of tool withdrawal. Compared with other CAPP systems, the information provided by the CAPP module of this system is more perfect and has a closer relationship with cam. In addition, due to the integration with MPS, the whole system is more practical and meets the requirements of virtual manufacturing technology and future manufacturing systems

Figure 3 system information integration figure

the processing feature description file provided by CAPP is the processing feature information extracted by CAPP according to the step neutral file provided by CAD and output to the cam system after process processing. It describes the general geometric information (such as hole depth, hole diameter) and position information (such as the azimuth of the feature)

4. Realization of machining process automation

in addition to the high integration degree of the cad/capp/cam/mps integrated system mentioned above, the cam module can automatically complete the machining process simulation and automatically generate the tool position file is another major feature of this system

its basic idea is shown in Figure 4: according to the characteristics of pro/m processing in pro/e, match each processing feature with a corresponding processing method provided by pro/m, and record the menu selection process and parameter requirements of each processing method. According to the feature processing method and feature parameters provided by CAPP, the cam system automatically generates the menu click file of the processing process, and sets reasonable control parameters in the menu click file according to the feature parameters. After executing the menu to click the file in the pro/e environment, pro/m automatically completes the machining process and generates the tool position file

Figure 4 automatic machining process

practice shows that the automatic realization of machining process not only reduces a lot of manual operations, but also improves the standardization and unity of machining method due to its high integration with CAPP. At the same time, because the cam system is integrated in the pro/e environment, the cam system can use other functions of pro/e (such as generating tool tables), which improves the practicality of the system

5. Conclusion

take the actual typical parts fb0103, fb05186, fb0288 of a factory as examples to verify the system. The time and workload of automatically completing the machining process and generating the tool position file are about 80% shorter than that of manually completing the machining. Using the functions of tool position simulation and NC code simulation, the generated tool position file and NC code are simulated by computer, which avoids the collision and interference of machining center and effectively improves the system efficiency. The practical application of the system shows that the integration scheme is feasible and reasonable, and provides practical methods and experience for the research of cad/capp/cam/mps of virtual manufacturing

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