Abstract: This article mainly discusses sheet metal structure design, process design and processing of our institute, combined with some experience accumulated in the implementation of CAD, CAPP/CAM work, and thoughts and ideas on several issues, and discusses sheet metal parts CAD/ The system composition, application characteristics and integration technology of CAPP/CAM can further exert the superiority of the sheet metal flexible manufacturing system. The design and processing of gold parts has its own structure, material and process characteristics. Due to the large variety of sheet metal parts and small production batches, the traditional design and processing methods used in the past have led to large design workloads, heavy labor, long processing cycles, and high costs, which cannot meet the needs of the increasing development of electronic equipment.
1. The composition and application characteristics of sheet metal CAD/CAPP/CAM system
With the introduction of advanced sheet metal processing centers and the development of computer technology, our firm is facing the problem of how to use them to increase production quality and increase productivity. At present, there are many CAD/CAM softwares specialized in the design and processing of sheet metal parts, such as SMP-81 of Merry Company in the United States, UG, RADAN in the United Kingdom, etc. From the function introduction and use of these software, they can usually meet The requirements of sheet metal design and processing can automatically connect the entire process from the design of the product circle to the generation of the CNC program. The composition of the CAD/CAPP/CAM system for sheet metal parts should be as shown in Figure 1.
Figure 1 Sheet metal unfolded view
1.1 Sheet metal mold parts design
The design of sheet metal parts includes parts such as three-dimensional design, two-dimensional design, graphics editing system, and CAD interface.
The 3D modeling module of sheet metal parts is a module specially designed and processed for the characteristics of sheet metal parts. It is based on the geometric characteristics of sheet metal parts, such as sharp corners, ring corners, upper bends, lower bends, and rounds. Hole, rectangular hole, square hole, long round hole, etc. for sheet metal part design. According to the tools provided by the CAD system, users can quickly and easily design the required rare maps. During the design process, the three-dimensional drawings of the parts and each plan are drawn on the screen at the same time. In order to observe and modify the design effects of the parts, the user can color the three-dimensional drawings of the parts. In the three-dimensional model of the part, a large amount of process, design and other information are included. Such as the thickness of the part plate, the bending fillet, the bending coefficient, etc., these process parameters ensure the absolute accuracy of the process development of the part. The structural design of the plate is related to the processing technology and equipment. The processing parameters must be considered in the CAD process, such as the minimum mold diameter, the thickness of the tree, the bending radius, the bending coefficient, etc., and the bending mold is used to determine whether the design is feasible .
The two-dimensional sheet metal design directly designs the three-view and flat unfolded drawing of the part, and the flat unfolded drawing can be directly used for process design, subsequent layout, and G code generation. The two-way arrows between the three-dimensional design module and the two-dimensional design module indicate that the parameters between the assembly and the two-dimensional part can be defined and transported to the intrinsic correlation. The modification of the two-dimensional graphics will automatically change the three-dimensional design, and the changes of the three-dimensional design will automatically be consistent with the two-dimensional graphics.
Due to the diversity of software choices, the selected sheet metal CAD/CAPP/CAM system should achieve smooth data exchange with other general mechanical application software. We can read the graphic files in the sheet metal CAD in DXF, IGES, PRT and other formats and convert them into the graphic files required by CAM for use by the Amad8 sheet metal processing center, or convert the sheet metal CAD graphic files to DXF, IGES, MI and other formats are used by other CAD and CAPP software.
1.2 Plane unfolding of sheet metal parts
Sheet metal parts have complex shapes, cumbersome manual expansion, and error-prone. They can be expanded quickly by relying on the software's automatic expansion function. As long as the required graphics and process parameters are correct, the expanded drawing is 100% accurate. When the discount factor or the thickness of the rice material changes, the system will automatically recalculate and get a new unfolded map. The expansion icon is marked with the positions of various holes, the position of the bending line, the position of each side, the number of holes and the geometric coordinates of each hole.
1.3 Multiple layouts of sheet metal parts
In the processing of sheet metal parts, craftsmen must study and solve the problems of maximum utilization of rice materials, less mold replacement and as short processing time as possible. To achieve this, reasonable layout and optimization of tool trajectories are very important.
In terms of optimizing the layout, the computer shows a stronger ability than the craftsman's manual layout. When nesting, the sheet metal software will automatically follow the processing conditions and the parameters of the machine tool. Quickly give out the layout result, layout diagram, including the number of layout parts, material utilization, and mold usage. The nesting software module can maximize the utilization of meal materials. If the production operation plan is reasonably arranged, some small workpieces will be placed in the holes of other large workpieces, which further improves the utilization rate of rice materials. In order to meet some special production requirements, users can modify and edit the automatic layout. At present, most of the sheet metal blanking in our institute is single-sheet trapped paper processing, and the process of cutting into single pieces or small materials is mostly used when preparing materials. The amount of clamping tools of the machine tool must be considered every time during processing, which greatly affects the utilization rate of materials. Therefore, it is best to consider the layout in conjunction with the production operation plan. After comprehensively considering the plan, the number of punches uses a variety of parts. The layout processing of large materials can maximize the utilization rate of sheet materials.
1. 4G code generation
The unfolded drawing of the part is input into the CAM module after layout, and the system processes various processing requirements, tool position information and machine tool characteristics in the tool position file to generate G codes that can be accepted by CNC machine tools.
In order to check whether the actual machining tool collides with the workpiece and whether there is an error program instruction, and avoid the damage of the tool and the machine tool, the reliability test of the CNC program is carried out by the method of machining simulation process. If there are still problems in the processing process, you can see it in the graphical demonstration of the mold and modify the G code until it meets the actual needs of the production.
Select the parts that need to be nested, set the quantity of each part and the designated equipment, automatically nest them according to the specifications of the material department, and automatically generate the G code of the entire material after nesting. The machining process can also be simulated. If there is no problem in the simulation plus two process, the G code will be transmitted to the CNC control cabinet of the cutting machine tool through the network terminal to prepare for machining call.
2. Integration of Sheet Metal CAD/CAPP/CAM System
System integration is to realize the timely exchange, transmission and sharing of system (or module) information. For the parts processing industry, it is to organically organize the geometric information and process information of the parts, so that the CAD data can be easily transferred to the follow-up modules such as CAPP and CAM.
In the process of research and construction of computer integrated manufacturing system (CIMS), people have gradually realized that the production process of products is actually the extraction, transmission and processing of data information. Therefore, the actual principle is the integration of CAD/CAPP/CAM in the CIMS environment. The problem is recognized as the key technology of CIMS, but so far this problem is still to be solved satisfactorily and effectively.
In order to realize the smooth and efficient use of Xinzhong in the system, it is very necessary to establish an ideal integrated system to coordinate the information between the various modules in the CAD system and the information at each stage of the entire product life process. The system should be able to reflect the entire process of the parts life cycle, so that data information is stored in a unified form, and summarized and managed; it should also have good graphics interactive processing capabilities and portability capabilities; it should be able to meet well Product design and characteristic model expression requirements.
In order to achieve the integration of the system and subsequent modules, it is necessary to describe and express the product from the different needs of each stage of the product's entire life cycle. From the point of view of information consistency, the model of the part is constructed so that the application field can directly learn from this Read the required information in the model structure of the part. The sheet metal system adopts a feature-based parametric design method for product design, and provides complete information for CAD/CAPP/CAM.
Our institute has introduced three major parts: punching, folding, and shearing of the sheet metal processing center, and randomly introduced the equipment-supported AMPUNCH-3D and 2D software for CAM. From the engineering technology department of the equipment manufacturing department of our institute, it is currently designed and used The software mainly includes AutoCAD, SoIid-Edge, etc. As far as the current situation is concerned, it is lack of necessary conditions to establish a complete CAD/CAPP/CAM system. Judging from the investment in technological transformation of our institute, this problem will be solved after the introduction of a full set of professional sheet metal software, which mainly includes CAD, design analysis, CAPP, CAM and other parts.
In the establishment of a CAD/CAPP/CAM integrated system for sheet metal parts, attention should be paid to information integration and resource sharing. That is, the system can use product design drawing information to be transformed into manufacturing process and production management information, and it can also drive the generation of NC processing instructions. The system can play the maximum benefit. In the whole system, CAPP is the link between CAD and CAM, and it plays a role in linking the past. In order to achieve CAD/CAPP integration, the required information must be entered for CAPP. The required information for sheet metal parts CAPP includes:
(1) General information, including the name, serial number, material, blank type, etc. of sheet metal parts;
(2) Geometric shape information, including the surface features, structural features, part dimensions and surface roughness of the basic geometric shapes of the parts, the position of the basic geometric shapes in the mold, and the primary and secondary relationship of surface elements.
The feature-based parametric design system is completely process-oriented, which can meet CAPP's demand for product information. CAPP reads the shape feature information and manufacturing and processing information in the CAD system, and uses this as the refined information, carries out logical reasoning, and interacts with the design process files to achieve the purpose of CAD/CAPP integration. The main function of CAPP/CAM integration is to convert the craftsmanship provided by the CAPP system into processing information, automatically generate G code, and then simulate processing after generating the G code. After the simulation is completed, the G code is transmitted to the CNC machine tool through the NC control system to achieve CNC processing. So as to realize CAPP/CAM information integration.
From the current cost-effective foreign sheet spare parts software, the CAPP part is not yet able to meet our needs. It can only solve problems such as process development of parts, automatic layout, G code generation, etc., but cannot generate processes for designated workshop operations. Process cards, process quotas and other process documents. At present, some domestic sheet metal CAPP software integrated with foreign sheet metal CAD/CAM software can basically solve the above problems.
3. Concluding remarks
Compared with other metal cutting and sectioning processing, sheet metal processing has its own characteristics and complexity. Sheet metal design and processing software is different from other general mechanical software. Pay attention to the design of sheet metal CAD/CAPP/CAM system The following points:
(1) Sheet metal CAD/CAPP/CAM software should include three-dimensional modeling of sheet metal parts, two-dimensional modeling, process development of parts, multiple layouts, automatic G code generation, process file generation and other modules.
(2) In the product structure design, process design and manufacturing process, information integration and resource sharing should be ensured. During process design and processing, the part drawing directly comes from the CAD structure design, no need; recalculation and input can quickly and accurately generate G code without occupying machine programming, and can reduce waste and increase the utilization rate of CNC machine tools.
(3) Pay attention to the role of product data management, and pay attention to the comprehensive consideration of the production operation plan with the car in the sheet metal processing process.