The Research Of Mechanical Assembly Modeling & Automatic Dimensioning Technique On Parts

Rapid development of computer science and extensive application of Advanced Manufacturing Technology are bringing radical changes to traditional manufacturing. At present, great breakthrough and resplendent achievement have been made in CAD ,CAPP ,CAM. But the development of tolerancing design in mechanical product has lagged behind them greatly. The actuality of tolerancing design can't adapt to the requirement of CAD/CAPP/CAM integrated developing and has become the bottleneck of their further development, which makes it necessary to do in-depth research on Computer Aided Dimensioning and Tolerancing(CADT). It is an important part in CADT field and of great significance in engineering to utilize computer to aid engineers to ascertain the suitable dimensioning mode, complete the automatic dimensioning of parts. In such a background, with the in-depth research on key techniques such as "assembly modeling", "application of dimension chain technique","research on dimensioning mode", the flexible application of correlative mathematical tools in Graph Theory, the utilization of relatively convenient ActiveX technique provided by CAD, the corresponding system has been developed to ascertain the functional dimensions and dimensioning mode, complete the automatic dimensioning of parts.In this paper, the following tasks have been accomplished: (1) Analyzing the constraint relation of parts to accomplish Oriented Functional Relationship Graph (OFRG) assembly modeling. (2) Utilizing the shortest path algorithm in Graph Theory to search functional dimension chains automatically in the assembly model and ascertain the functional dimensions of the part.(3) On the basis of the dimensioning principle of correctness, integrality, clearness and rationality, utilizing the modified spanning tree algorithm in Graph Theory to ascertain the non-functional dimensions, accomplish the dimensioning mode analysis of the part.(4) Automatically grouping dimensions by their directions, accomplishing the priority level enactment of dimensions and implementing the optimal lay of dimensions on the part drawing under the CAD environment.(5) Use the example to introducing the entire implementing process of the mechanical assembly modeling & automatic dimensioning technique on parts in detail.