Volume Based Approach to Extract 3-D Parts from 2D Assembly Drawing

Abstract

This paper extends an earlier volume-based approach to automatically reconstruct 3D parts from the 2D orthographic views of an assembly drawing. Most of the work in automatic reconstruction of 3D solids using volume-based approach from 2D orthographic views has been done only for single component drawings. The proposed method identifies elementary solids called candidate blocks from the orthographic views and then combines these solids to obtain different parts in the assembly. The candidate blocks are combined on the basis of some conditions defined based on the validity of solids and characteristics of an assembly. Earlier efforts towards addressing multi-part assembly drawing either require additional inputs in the form of labeling of parts in the drawing, additional special cross-sectional views or are restricted to assemblies with standard parts. Results have been achieved for some typical engineering assembly drawings. Future work will address extension of this algorithm to assembly drawings with sectional views.Keywords: assembly drawings, 3D parts, orthographic views, volume-based INTRODUCTIONConventionally an engineering drawing has been a means to store information about complex 3D parts in 2D form. The drawing contains all the required information about the 3D object in an accurate, concise and systematic way. In industries, there is huge legacy of data and product information available in the form of engineering drawings (either in the hard copy form of blue prints of drawings or in the digital/soft form generated by available computer-aided drafting tools), which are continuously used in new product development. This form of shape representation continues to increase due to its familiarity for users and consequent ease in manipulation. Understanding engineering drawing requires a thorough knowledge of the rules and conventions of engineering drawing and industry/organization specific protocols. As the complexity of the drawing increases (sectional views, auxiliary views), the skills required for interpretation also increases. A 3D solid model is becoming essential for other design tasks such as CFD/FEM analysis, rapid prototyping, and simulation. Automatic construction of 3D solid model from 2D drawing is of great importance given the penetration of 3D models in product development tasks and the specialized skill required to manually interpret the drawing. Automatic conversion of 2D views of engineering drawings into 3D model has been a challenging and popular problem in CAD area. Since 1980, many methods for reconstruction of solid model from orthographic views have been proposed and implemented. The approach for automatic reconstruction of a solid model from a 2D engineering drawing can be broadly classified as: