Machining Path Generation System of a B-axis Fixed Plane for a Four-Axis Machine Tool

四軸加工機之B軸定平面切削路徑規劃系統開發之研究

林浩庭(Hao-Ting Lin) ； 劉鎮頡(Jhen-Jie Liou)

《中國機械工程學刊》 38卷6期 (2017/12) Pp. 589-595

摘要

The four-axis turning-milling multitasking machine is a new machining platform; its main structure has three linear axes (X, Y, Z) and one rotational axis (C). This type of machine has various advantages including superior accuracy, superior efficiency, and a small footprint. However, due to the lack of a B-axis, this type of machine encounters difficulties when machining features on tilted planes. The present work developed value-added software for the Windows operating system to solve the aforementioned challenges. This research used homogeneous coordinates to transform existing three-axis machining paths into machining paths for fixed tilted planes. The C♯ programming language and Visual Studio were used to complete the development of a human-machine interface (HMI). Each machining path was controlled by a C♯ function. A homogeneous coordinate matrix was coded in C♯ programming language to reuse all coordinates, because when transforming from a horizontal plane to a tilted plane, the program requires a rotation matrix for the global Y-axis and a rotation matrix for the current X-axis. The software developed in this research was verified through NCPlot, Vericut, and AutoCAD. The results of the exported program and a numerical experiment differed by no more than 1 μm. The software developed in this research was used to CNC machine by a physical work-piece. The physical work-piece results confirmed the practicality of the software.

關鍵字

CNC multi-axis machine tool ； b-axis ； machining path planning ； vericut ； homogeneous coordinates

並列摘要

四軸車銑複合機是一種新興的加工平台，主要結構為三個線性運動軸(X、Y、Z軸)及一個可旋轉定位之分度軸(C軸)，具有提升精度、提升稼動率、縮減占地面積等多項優勢，但由於缺少B軸，故B軸上的傾斜幾何無法輕易被加工，本研究即是基於上述問題而發展出了一套PC加值軟體。本研究開發之軟體將可在「不增加成本」的情況下延展多軸切削機的加工性能，本研究係利用齊次座標將系統內規劃的三軸切削路徑轉換成傾斜定平面(Tilt fixed plane)加工路徑，此外本研究中推導出底面銑削表面粗糙度之理論公式，並且使用C♯平台進行人機軟體開發，此斜面切削軟體功能包含四大切削特徵和表面粗糙預測，人機介面主要是以對話表單的方式呈現，使操作者有簡易的操作環境。本研究之斜面切削軟體流程為將切削路徑寫成函式，並將轉換矩陣放在Method中重複使用，由於需將路徑函式從平面轉換到斜面，所以需將世界座標之Y軸對當前座標X軸旋轉。驗證則運用NcPlot、Vericut和AutoCAD軟體檢驗，實驗結果顯示準確度為1μm之內。