Abstract: To solve the problem of adapting STEP-NC technology to multi-axis surfaces machining,the instruction for 5-axis machining of freeform surface was defined in STEP-NC data model,the 5-axis real-time interpolation for NURBS surface was researched,and the kinematics model of CNC system which included path planning,tool offset,real-time interpolation and inverse of Kinematics transformation was built up.On these bases,the software of CNC system was implemented,and the 5-axis prototype milling machine with the experiment for cutting NURBS surface part were developed.Experimental results showed that the definition of instruction in STEP-NC and the proposed kinematics model for 5-axis NURBS surfaces machining were correct,the interpolation algorithm was applicable for machining of convex and concave surfaces,and the prototype for 5-axis milling had good performance of cutting free-form surfaces.

Key words: STEP-NC, NURBS surface, interpolation, 5-axis machining, numerical control system

摘要： 针对当前STEP-NC尚不能完善地支持多轴曲面加工问题,定义了STEP-NC中的自由曲面五轴加工指令,研究了非均匀有理B样条(NURBS)曲面实时五轴插补技术,建立了数控系统的运动学模型,并在上述理论研究的基础上完成了数控系统的软件设计;建立了五轴数控试验样机,并进行了NURBS曲面零件的切削实验。实验结果表明,所提出的基于STEP-NC的NURBS曲面五轴加工指令及NURBS曲面五轴加工的运动学模型的正确性;所给出的NURBS曲面插补算法适用于凸凹曲面加工;所构建的五轴铣床样机具有很好的曲面加工性能。

关键词: STEP-NC, NURBS曲面, 插补, 五轴加工, 数控系统