Research On The Free Form Curve And Surface Interpolation Technology Based On The SETP Standard

With the development of the manufacture, auto control, micro-electronics, data processing and etc, the new opened numerical control technology will take the place of the conventional one. In the system of numerical control, the function of the interpolation affects the appraisement of the whole system of CNC. In the modern manufacturing, the request of the quality and the quantity in the free form curve and surface grows, so it is necessary to research the directly interpolation of the free form curve and surface, not only to improve the efficiency and the quality, but to adapt the development of the modern numerical control technology.The STEP standard is a series of international standard,which apply to computer to express and exchange the product datas。The goals of STEP are to establish a standard that integrated, realizing, neutral and can be managed by computer to express the product datas of the whole lifecycle.meanwhile,can independence of any special systems. Thanks to its good mathematic feature, so was ordered to an exclusive form that can be express the curve and face in the STEP standard. What's more, in the field of CAD, NURBS has been well used.So based on the STEP standard and make use of the NURBS to express the curve and face.Then research the curve and surface interpolation technology.At first,this paper analyzed the STEP standard,researched on the STEP standard in the light of the composing, configuration,context and the EXPRESS language.In order to carry out the further work, in the light of the exchange form, configuration and the data context,researched on the STEP neutral exchange file that is very important to the STEP standard,and make use of the method of combination to obtain the data model of the NURBS curve and surface in the STEP standard,then made the relevant entity class mapped to the C++ class.Bsed on these work,make use of the VC++ to develop a system that can pick-up some geometry datas with respect to the NURBS curve and surface. In the process of research on the NURBS curve interpolation technology.firstly, processed the geometry datas of the NURBS curce that picked-up former.Then,based on the equal arc interpolation thought,this paper developed a newer NURBS curve interpolation arithmetic.This arithmetic can consider the precision factor and automatically adapt the feed speed according to the change of the curve curvature, realizeing the curve uniformity interpolation.Meanwhile,researched on the add- reduce speed control methods,introduced a newer add-reduce speed control method that can be used in the NURBS curve high speed machining,make sure of the calm change of the acceleration.In the process of research on the NURBS surface interpolation technology. Firstly,introduced and compared some tools location contrail that often used on the surface machiningBased on the equal parameter line arithmetic,developed a newer arithmetic.And predigest the method that can calculate the distance of the two tools location contrail,Then, summarized the whole flow of the arithmetic.This arithmetic can control the distance of the two tools location contrail in the some bound and can make the tools location contrail were fulled in the surface.