The Study On Assembly Tolerance Accumulation Path Based On UG Platform

In the process of mechanical product design and manufacturing, in order to meet the accuracyrequirement and function of mechanical product requirements, we need to do further analysis andoptimization in the size range, make its machining precision to meet the economic purpose, that istolerance analysis and synthesis. As mechanical products gradually developed to the direction ofmultifunctional and high precision, tolerance is becoming more and more widely applied, using thetolerance can reduce the cost of manufacture and can meet the functional requirements of themechanical products, the tolerance design also gradually become an indispensable link in theprocess of mechanical product design. With the development of Computer technology, ComputerAided Tolerance design (Computer Aided Tolerancing, referred to as "CAT) technology is appliedto the mechanical product tolerance design link, greatly reduce the design time; decrease theworkload of the designers and design cost.In recent years, there is a lot of research has been made to study the tolerance, the results arevery much also, but the conclusions are not perfect. In this paper in view the problem of theassembly tolerance accumulation, by combining the knowledge of data structure, we did someresearch about tolerance accumulation of3D assembly using VC++as the secondary developmentenvironment based on the3D software UG NX7.5, main content has the following several aspects:(1) The extraction of the UG3D assembly model of geometric tolerance information. Based onVC++6.0programming environment and UG/Open API module which based on UG NX7.5system,we just design the user custom applications which call the UG API functions to realize the theextraction of the geometric tolerance informationof3D assembly model, which has been marked inaccordance with the design requirements.(2) The3D assembly model geometry information storage and the establishment of therelevant data structure. Combined with the data structure and knowledge of graph theory to fullfillthe storage of the3D assembly geometric tolerance information storage, and based on this we buildthe assembly tolerances graph of the assembly model. The tolerance figure includes geometrictolerance information of assembly components, such as dimensions, geometric tolerances, datuminformations, etc., as well as the assembly relationship between assembly components.(3)In3D assembly tolerance figure, which was based on we design the assembly toleranceaccumulation of path graph algorithm. Mechanical products in the process of assembling alwaysmeet certain requirements of assembly; run the algorithm by selecting two geometrical elementswhich belong to two assembly components which releated with the assembly requirements as thestarting point of the search, then traverse the entire assembly tolerance chart, and output graph node related to the assembly requirements, final output assembly tolerance accumulation of the results ofthe path.(4) The example verification. The assembly tolerance accumulation path diagram provide abasis which can be used to do tolerance analysis to draw some releated conclusions andoptimizations, verify the feasibility of what the paper mention that the research based on UG NX7.5established three-dimensional about the3D assembly tolerance accumulation effect.