Convert BSpline Curve to Arc Spline in OpenCASCADE
Abstract. The paper based on OpenCASCADE algorithms to approximate the NURBS curve to arc spline. The method is most useful in numerical control to drive the cutter along straight line or circular paths. Or in the shipbuilding industry to manufacture section bar for cold frame bender. Key Words. NURBS, Biarc approximation, arc spline, 1. Introduction 在数控加工CNC领域，通常需要用尽量少段数的圆弧和直线段来对曲线进行拟合。有的数控绘图机也只有直线和圆弧插补器，即只能绘制直线和圆弧，所以也需要将自由曲线转换成直线和圆弧来进行绘制。在船舶制造方面，如肋骨冷弯机只有两种状态：弯和不弯，也只能加工出直线和圆弧，所以也需要将曲面型材的弯曲信息转换成肋骨冷弯机能加工的数据。如下图所示为型材模型及其基线： Figure 1. 型材模型及基线 Figure 2. 肋骨冷弯机 如上图所示，型材都是直线的，通过弯曲加工出曲线效果