CAD modeling for tubes in industrial design

Tube surfaces are the complicated surfaces generated by smoothly joining together several cylinders. Most kinds of industrial design models are tube surfaces in production. To meet the needs of composite materials in some industrial design, it is necessary to make the representation of the tube surfaces as simple as possible. Based on the theory of implicit surface modeling, the global modeling methods for the tube surfaces of elbow and Y-tube are presented, the influences of parameters on the blending surfaces are discussed and the concave-convex characteristics of the blending surfaces and control surfaces are studied in this paper. On VC++ software platform, using Open Gl, the tube surfaces of elbow and Y-tube are implemented with a computer by the steps of gathering the data points from the implicit expressions, forming triangular mesh and fairing the triangular surfaces. The research results are very important for craft and technique of the products.