The Study And Application For NC Machining Of Freeform Surface Based On Reverse Engineering

With the quickly development of industry, there is more and more complicated shape product which have freeform surface and be demand more and more precision. The NC machining has already been the main technology for its production. These products always have no ready drawing and CAD model. Reverse engineering, which has developed in recent years, has become an important method to obtaining CAD model for these product. So, it is widely used for NC machining technology based on reverse engineering of freeform surface in many fields, such as aviation, automobile, mold as well as art.This paper has made an academic study and practical application for the collection method of three dimension data and measuring data preprocessing as well as surface rebuild, and also include tool path generation of NC machining.In this paper, the collection of three dimension data and the plan of measure area along with measure point distribution are analyzed. In addition, the measure data preprocess and relocation conformity has been discussed. There are two mainly method for surface rebuild, one is based on three angular Bezier surface, the other is B-spline or NURBS surface. The property of B-spline and NURBS curve is introduced and how to generate curve and surface with interpolation is studied.This paper bring forward the type of freeform surface based on differential geometry and made a more particular discussion to property of flat tool, especially for strategy and method of tool path generation, such as Iso-planar and Constant scallop-height along with Iso-parametric line. In order to improve the precision of freeform surface, the error of multi-axis NC machining is analyzed and a more reasonable estimate for tool step is given. At last, the reverse and NC machining for a freeform of head is applied for aforementioned study.Anyway, reversing and using CAD/CAM system to generating NC program is a advanced manufacture technology for freeform surface part, it can improve flexible and accuracy. This study will enrich the theory of reverse technology and NCmachining of freeform surface and promote its application a certain extent.