Research On The Accuracy Of Entity’s Dimension On2D Engineering Drawing

Along with the development of CAD/CAM technology, more and more researchers focus their work on how to recognize feature of graphics automatically on the drawing, and they want to obtain feature information of graphics accurately. Due to3D (three-dimensional) model design adopts parametric design; the feature of graphics recognition has achieved remarkable progress in researching. But, at present,2D (two-dimensional) model does not adopt parametric design which is also widely used all over the world. The feature of dimensions and graphics are not ensure them exact matching on the2D drawing, so the feature of graphics recognition alone cannot make sure the parts’sizes are accuracy. Although there are many methods to recognize the feature of graphics, the work progressed at a slow pace. The mainly reason is the feature of graphics are researched individually rather than dimensions and graphics together.In order to solve this problem, this paper takes widely used2D software AutoCAD as development platform, researching on the accuracy of entity’s dimension on2D drawing to ensure feature of graphics recognition automatically are accuracy. Firstly the article discusses sorts of AutoCAD second development tools and analyzes the respective characteristics of tools, selecting the development tool best suited to paper needs. Secondly according to AutoCAD help document, this thesis studies software database. And according to mechanical drawing national standards (GB4448.4-84), this thesis also studies various types of dimensions and styles of dimensions. To recognize features of dimension, this article presents two methods:Some are for commonly dimensions. Due to these dimensions have whole feature, so it can be used conventional algorithm to recognize. The others are for exploded dimensions. Due to these dimensions have not whole feature, so this article puts forward a new method to recognize exploded dimensions. Association rule mining algorithm is added in the process of recognition; it can recognize exploded dimensions step by step with association relationships of basic elements of dimensions. Finally this article researches the relationship between dimensions and graphics, discussing how to check graphics sizes cooperate with dimension text and geometry property. And then some examples are provided to illustrate the efficiency.