Research on the most popular visual virtual assemb

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Research on visual virtual assembly system and key technologies

Abstract: virtual assembly is one of the key technologies of virtual manufacturing, which can be pre assembled in the product design stage to verify the correctness of the assembly process.) the visual virtual assembly system based on SolidEdge, through secondary development, should have the following functions: assembly path setting, assembly parts position and posture adjustment and hidden, assembly perspective adjustment and view zoom Virtual simulation setup and other functions) the overall structure of the system includes modules such as assembly modeling initialization, assembly process file acquisition, assembly process animation and simulation) its key technologies include: releasing CAD assembly constraints, and extracting 6-tuple position and posture information of virtual assembly parts; Virtual assembly weight drawing based on 6-tuple information and its assembly process simulation: database organization of information including virtual assembly parts, assembly bodies, assembly paths and priorities, angular posture, assembly key point coordinates and angles around coordinate axes)

Keywords: virtual assembly; Assembly simulation; Visualization; Virtual manufacturing

virtual manufacturing (VM) is one of the research hotspots of advanced manufacturing technology [1]) VM is the mapping of real manufacturing in the virtual environment. Its essence is to use simulation technology and interactive three-dimensional visual model to quickly iterate over virtual products on the computer, Make all aspects of performance (such as working performance, manufacturability, assemblability, etc.) in the whole life cycle achieve balanced optimization and improve the ability of prediction and decision-making. Virtual assembly is one of the core technologies of virtual manufacturing [2]. It carries out the simulation demonstration of product assembly process after obtaining product information and product assembly process information, and provides a visual interactive environment for assembly process planning, So as to effectively improve the assembly process and assembly quality of products)

1 function analysis of visual virtual assembly system

1.1 mainstream CAD: the assembly description function of the system

visual virtual assembly is realized through the operation of product assembly models.) there are many mainstream 3D CAD systems that can establish product assembly models, typical of which are UG, pro/engineer, CATIA, Solidworks, SolidEdge, etc, These CAD softwares all provide sketch, part design, assembly design of components and assembly design modules. During the assembly design of components, the assembly relationship description provided in the system can be used to define the assembly relationship of components. These assemblies include face-to-face, face-to-face and axis alignment, which basically meet the constraint requirements of assembly relationship in the assembly process design of electromechanical products

the virtual assembly simulation system is parasitic on the realization of CAD system. It can use the development tools provided by the existing CAD system, such as MDT and AutoCAD. Object ARX class library is provided for visual c++ development, SolidEdge provides OLE automation for visual basic development, and pro/engineer has developer and Toolkit development modules

1.2 function analysis of visual virtual assembly system

as a parasitic virtual assembly simulation system, its implementation is based on the existing CAD environment, making full use of the functions provided by the existing CAD environment, plus new function development to meet the system requirements

through the secondary development of CAD system, its virtual assembly module has the setting of assembly path in the assembly environment: the adjustment of assembly posture of parts during assembly: the blanking of relevant parts in the assembly can be carried out during the assembly of parts; it can provide the adjustment of observation angle of users in the assembly process, provide the function of user view zoom, etc., and the setting of virtual simulation in the assembly process, It is carried out by the assembly process designer in the assembly process design system

2 overall structure of visual virtual assembly system

the visual assembly module proposed in this paper is based on SolidEdge combined with active X technology to extract assembly model information. Under the guidance of assembly process, the assembly path setting is realized, and the visual virtual assembly

simulation process is established [3], Its overall structure is shown in Figure 1:

Figure 1 overall structure of the visual virtual assembly system

from Figure 1, it can be seen that the visual assembly simulation system is composed of the following modules:

assembly modeling initialization: call in and confirm the target assembly SolidEdge to extract the basic modeling information required for virtual assembly, such as the name of parts, part files, structure level information, cooperation constraint information, etc, Store it in the data structure

viewing and obtaining assembly process files: extract the assembly process files of the corresponding assembly from the assembly CAPP system as the necessary input of the virtual assembly process

establishment of virtual assembly: This is the core module of virtual assembly technology preparation, from which the setting of virtual assembly environment and the initialization of assembly path, the setting of assembly path, the posture and position of parts, the adjustment method of angular posture of parts in the assembly process, the priority of assembly path, etc. are carried out. In addition, the interference inspection on the assembly path is also carried out

assembly process animation: after the preparation and setting of the virtual assembly demonstration, the assembly process can be demonstrated along the specific assembly path of a single component, multiple components and all constituent components according to the set assembly posture angle, and the animation shows the motion effect. Assembly simulation verification: display the assembly simulation results, motion interference inspection, analysis of motion rationality, etc, Simulation result report: the assembly in text mode is generated to meet the needs of precise direct extrusion of plastic products, including process documents, interference inspection reports, and assembly paths in graphic mode

3 some key technologies and implementation methods of visual virtual assembly system

3.1 part assembly information extraction technology in virtual assembly

in order to extract and remember the position information of parts in the assembly, before deleting the assembly relationship, the attribute chain of SolidEdge object parts transform is used to extract the position and posture information of all parts in the assembly, And store these information in the product basic information database. These data are used as the final pose constraints of components in the assembly simulation process. In SolidEdge, corresponding to the two objects of part and assembly, the commands available for calling are gettransform, puttransform, putorigin, and getorigin. The gettransform command can obtain the coordinate position and deflection angle of the component base point relative to the coordinate axis of the assembly environment coordinate system. The parameter form of this command is ttransform (originx3d printing material suppliers are also trying to explore, originy, originz, anglex, angley, anglez)

when extracting the pose information of product parts, the virtual assembly module needs to first remove the assembly constraints in the CAD assembly design environment. At this time, the position coordinates of the components in the assembly environment can be retained as the base point coordinates obtained by the assembly relationship constraints when adding the assembly, but the component posture position will no longer retain the posture controlled by the assembly relationship constraints, but will be displayed as the component posture set by the virtual assembly module

in SolidEdge, the position and posture of components are described by six tuples, which can comprehensively represent the position and posture information of assembly components in the SolidEdge assembly environment. The meanings of various parameters in the six tuple method are shown in Table 1: Table 1 interpretation of the meaning of six tuples

3.2 virtual assembly simulation implementation technology

when designing assembly simulation in SolidEdge assembly environment, the position and posture of parts and components are determined by setting the specific variable values of six tuples. When setting the position and posture of assembly components in this way, first remove the assembly relationship related to the components, and add the ground relationship to the components, so as to determine this component as the benchmark of the assembly. After deleting the assembly relationship in the assembly file of the product, the angle and posture information of the parts is lost, leaving only its original posture information. Therefore, the user needs to set the posture angle at the beginning of the assembly demonstration. After the parts get the accurate assembly position and posture in the product with the ground assembly relationship alone, the system obtains and resets the position and posture of the parts, and redraws the assembly, so as to realize the assembly process simulation

in order to realize the simulation effect of virtual assembly process, by adjusting the position and posture of parts, the large segment deviation movement and large angle deflection are transformed into small multi segment deviation and deflection, and the single-step simulation of virtual assembly process is realized! By continuously extracting the position and posture of each component, rewriting the position and posture in motion, and finally resetting the position and posture and displaying the operation of the component, the continuous simulation of the assembly process is realized

3.3 data organization mode of the database in the virtual assembly process

the system uses database files to store the assembly path and the position and attitude of parts set in the virtual assembly process, and stores the number of assembly paths set, path order, start and end points of the path, coordinate movement order in the path, part attitude and attitude change mode in the assembly process in the database record. When setting the virtual assembly, the system outputs all these useful information to the temporary database records through the interface provided by the system. After the demonstration, these information will be written into the database record after the user determines. See Table 2 for the structure of virtual assembly path data table. Table 2 structure of virtual assembly path data table

when users choose to simulate the assembly process, according to the assembly priority of the assembly parts, the system looks for the corresponding records in the database, and submits the data information about the assembly simulation, which is no longer true, to the simulation program to form the assembly simulation process

4 conclusion

virtual assembly is one of the key technologies of VM. The visual virtual assembly system based on SolidEdge proposed in this paper can realize the pre assembly of virtual products through the simulation of assembly process at the stage of product design, verify and improve the assembly process of products, vividly and intuitively show the assembly ability of products, and can be used as one of the supporting tools for VM implementation


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