本論文針對五軸曲面加工的應用場合，秉持ISO 14649 STEP-NC的物件導向精神，擴充了ISO 14649文件中對於五軸自由曲面及曲面曲線的實際特徵加工命令定義，並設計出一套STEP-NC五軸銑床曲面加工任務展開模組。在完成STEP-NC五軸加工命令擴充後，CNC內部獲得足夠的幾何特徵描述，在控制器中的解譯器擷取曲面及曲面曲線加工特徵描述指令，並自動展開為刀具之引導軌跡。至於刀具指向在簡單無衝擊危險情況下可根據曲面局部曲率特性，計算刀具在軌跡切線方向的前傾角，或是為了避免衝擊並節省複雜的前傾角計算，刀具指向也可由三個在軌跡上運動的參考座標所定義的轉動角決定。最後所計算出的刀具路徑及五軸刀具指向則以適當CNC參數規範，粗插補成刀具路徑曲線及五軸刀具指向曲線送入即時插補器的暫存器中。

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.

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