Abstract
Base on the object-oriented concept of ISO 14649 STEP-NC, this paper expands the specification of ISO 14649 standard for the five-axis machining of free-form surface. The structured commands for the five-axis milling of NURBS surface and curve on surface are defined and the operation modules to automatically unfold these commands are designed. In order to prove the feasibility of STEP-NC based five-axis machining of free-form surface, the interpreter for the interface have comprehensively designed and realized.