Tool Path Planning Of NC Machining Based On Circular Surface Tool Free Surface

With the rapid development of technology, in shipbuilding, aerospace, automotive and electronics industries,the requirements for product appearance are increasingly more and more complex, more and more personalized. So free-form surfaces are widely used in these industries. The complexity of the free-form surfaces put a lot of processing requirements. Due to high precision free-form surfaces and difficult to accurately be described mathematically, freedom of research and its surface toolpath generation technology is the focus of CNC machining. In this context, this paper is about tool path in torus tool CNC machining.As the only standard on data exchange of products allocated by ISO, NURBS is more dominant than the other spline methods. So, NURBS is chosen to be the representation model of free-form surfaces and the relative theories on geometric modeling and differential geometry are to be described.The emphasis of NC programming is tool paths planning and generating. Economic benefits can be directly brought by a set of optimal tool paths. So, in this paper, an algorithm for tool path generation is proposed based on thoroughly approaching to the local differential geometric structures of the cutting tool and the machined surface.The tool path planning algorithm which is proposed in this paper is combination of iso scallop height and variable step. Tool path is actually a collection of cutter location data according to certain rules. So tool path planning is a process to calculate the cutter location point. On the basis of space graphics transformation, this paper established a cutting model of torus tool and free-form surface and studied the scheme of conversion between a cutter location point and a cutting contact point.The difference of tool path planning is mainly the different calculation methods of step and spacing. To plan tool path, firstly, the calculation methods of step and spacing are determined. Secondly, we should select the longest boundary line as the initial tool path. Thirdly, we should discrete surface boundary into a series of cutter contact points and then calculate corresponding cutter contact points of adjacent toolpath according the formula. Finally, according to the conversion formula, the cutter contact point will be converted to the cutter location point and then these points fit a toolpath. Additionally, mathematical modeling of free-form surface is established, and then the path planning algorithm is implemented by using Matlab programming. The cutter location points for torus tool are calculated by Matlab, and then fit these points to a toolpath. While using UG software another toolpath of free surface is simulated of the same data. It is drew compared the two toolpaths that using torus tool is more efficient.