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Research on the application of virtual assembly technology based on CATIA system

virtual assembly technology is the process of controlling the overall design process of products and defining and analyzing specific models under the virtual design environment. It can effectively support top-down concurrent product design and design for manufacturability and assembly related to master model, so as to shorten the product development cycle. After analyzing the basic idea of virtual assembly technology, this paper puts forward the basic environment and specific implementation methods and approaches for the application of virtual assembly technology in aircraft design

"virtual assembly" is an important link in the definition of product digitalization, and has been widely used in the field of virtual technology and simulation. What is virtual assembly? What is its connotation? These are still the problems that people discuss. Many people have defined virtual assembly, and there are two representative ones

(1) virtual assembly is a process of repositioning the part model according to the constraint relationship, and it is an effective means to analyze the rationality of product design. This definition emphasizes that virtual assembly technology is a process of model relocation and analysis

(2) virtual assembly is to truly simulate the three-dimensional assembly process of products according to the shape characteristics and accuracy characteristics of product design, and allow users to interactively control the three-dimensional real simulated assembly process of products to test the assemblability of products. The definition focuses on the simulation process of the physical assembly process of products, and the idea embodied is also an analysis process

obviously, the above definition emphasizes different aspects, but as a new concept, the proposal and implementation of new technology must be combined with specific industry design characteristics to have practical significance and real connotation. Therefore, combined with the characteristics of aircraft development, this paper gives the following definition: virtual assembly is a design process that completes the solid modeling of aircraft parts on the computer, carries out computer assembly, interference analysis and other coordination for many times, and realizes a high degree of unity between the three-dimensional design process of aircraft and the manufacturing and assembly process of aircraft parts through unified product data management. Virtual assembly technology is a new design concept in the application research of aircraft. It provides a new design method and implementation approach for aircraft development. Its success depends on the control of the overall design process of aircraft. At the same time, the reasonable flow and sharing of aircraft component model data is the basis of virtual assembly technology

in aircraft development, virtual assembly includes three parts: design process, process control and assembly simulation

II. Basic design idea and connotation of virtual assembly

1 Design centered virtual assembly refers to the application of three-dimensional digital definition of products in the process of product development, combined with the specific situation of product development, highlighting the application idea of taking design as the core, which is reflected in the following three levels

(1) DFA product development process is a complex interdisciplinary and interdisciplinary system engineering, which requires overall coordination in the early stage of product development, that is, the design stage, mainly to analyze the feasibility and rationality of the product collaborative work process, and to evaluate the case of regular replacement of oil absorption filters and filter elements in the physical assembly formula of the main structure of the product. The traditional design process is seriously divorced from the assembly process, and assembly oriented design (DFA) method needs to be adopted, that is, the product design process is organically combined with the manufacturing and assembly process at the initial stage of design, so as to ensure the assembly of products from the perspective of design. By introducing the design idea of product assembly process, the designed product has a good structure, can be physically assembled efficiently, and can make the design department and the manufacturing department work together more effectively in the early stage of product development

(2) top-down concurrent product design (CPD) assembly technology based on concurrent product design supports the top-down design method. Through top-down concurrent product design, a unified product dynamic electronic prototype can be established hierarchically

concurrent product design is the integrated and parallel design of products and their related processes. It emphasizes that developers should consider the influence of all relevant factors in the whole life cycle of products from conceptual design to extinction from the beginning, and find all possible errors and contradictions as soon as possible, so as to shorten the product development cycle, reduce product costs, and improve product quality. The focus of concurrent product design is the collaborative concurrent design of multiple integrated product teams (IPTS). Product design engineers distributed in different places and departments are required to highlight the design idea of taking products as the core and carry out concurrent design from different angles and different requirements

(3) design for manufacturability and design for assembly related to master model. The master model at different stages of product development provides an assembly design environment for design groups, so that the design of each member of the design group is effectively controlled within the range of final product assembly from the beginning of product design, and realizes the design idea of highlighting the product as the core, Ensure that the work of the product design engineer is related to the progress of the whole product, and the changes of the component model will only be reflected on the corresponding assembly components, so as to ensure the integration of model data and avoid the repetition of design work. At the same time, product development is a collaborative work process of multiple departments. The cooperation between the main engine factory and the auxiliary engine factory is often limited by the production conditions of various enterprises. Combined with the producibility and production characteristics of various enterprises, it is very necessary to improve the manufacturability and assembly of product design models, reduce the number and special types of component models, reduce the types of materials, and use standardized and modular components. Taking the master model in different stages as the core can ensure the integrity and consistency of the data structure in different stages of product development, ensure the collaborative work of various departments of product development, realize the high integration of cad/cam/cae system, and effectively improve the manufacturability and assemblyability of products

2. Virtual assembly centered on process control

process centered virtual assembly mainly includes the following two aspects:

(1) realize the control of the overall design process of products. In the process of product digital definition, combined with the characteristics of product development, we artificially divide the application of virtual assembly technology to the product design process into three stages: the overall design stage Assembly design stage, detailed design stage. Through the control of the three design stages, the overall design process of the product is controlled, and the virtual assembly design process is realized

1) overall design stage the overall design stage is the initial stage of product development. In this stage, the preliminary overall layout of the product is carried out, mainly including:

☆ establishing the master model space

☆ carry out the preliminary structure of the product and the overall layout of the system

2) assembly design stage assembly design stage is the main stage of product development. At this stage, the product 3D solid model design has been basically completed, mainly including:

☆ product model space allocation (assembly area, assembly level division)

☆ specific model definition (establish geometric constraint relationship, three-dimensional solid model, etc.)

☆ stress control

3) detailed design stage the detailed design stage is the improvement stage of product development. In this stage, the final design of the product 3D solid model is completed, mainly including: the final design of the product 3D solid model is completed, the computer assembly of the product model is carried out, and the whole machine interference inspection is carried out

4) the process control management process model includes the process description of product development, the relationship within the process and the cooperation between processes. We hope that through the effective management of process models, we can realize the management of product related information such as product design results and processing technology in the process of engineering development, so as to realize the purpose of optimizing the product development process

3. Simulation centered virtual assembly is to integrate simulation technology into the product assembly design model to evaluate and optimize the assembly process. Its main objective is to evaluate the product's assemblability

(1) the purpose of optimizing the assembly process is to make the product adapt to the specific local conditions, and divide it into assembly units reasonably, so that the assembly units can be assembled in parallel

(2) assemblability evaluation is mainly to evaluate the relative difficulty of product assembly, calculate the assembly cost, and decide whether the product design needs to be modified

III. application research

1. basic application environment

the application of virtual assembly technology in aircraft design requires a certain basic application environment as a platform, which mainly includes the following aspects: collaborative work environment, unified PDM and information coding system, general aviation basic standards and system integration environment

(1) collaborative work environment aircraft development process is actually a repeated coordination process among multiple departments, disciplines and systems. In aircraft development, engineers of every profession and department, due to the constraints of professional and subjective factors, will always give too much consideration to the performance indicators of a certain aspect of the aircraft, while ignoring the comprehensive performance indicators of the aircraft. Therefore, there is a basic environment for collaborative work to achieve a working environment that supports remote design, remote assembly and remote testing, especially the remote rapid transfer, process control The basic environment of human-computer interaction is very necessary

(2) the aircraft design of unified PDM and information coding system is a complex system engineering. The reasonable flow of various engineering data within and between IPTS and effective management are important links to realize virtual assembly technology. It must be able to realize the collaborative design of cross network platforms and the "plug and play" of application tools. Others include the automotive industry, small and medium-sized electronics and home appliance manufacturing industry, as well as the application of