- 會議論文
CNC五軸切削進給率設定最適化研究
Study on Feedrate Setting Optimization in CNC 5-axis Machining
摘要
電腦數值控制(CNC)五軸加工機除了三個線性軸外還增加了二個旋轉軸，適用於某些複雜元件如葉輪、凸輪等的切削；應用五軸加工機可以簡化或避免工件重新定位、夾持的問題，以獲得高效率加工及高精度成品。進行三軸或五軸曲線路徑切削時，CAD/CAM系統通常先將曲線路徑分割成許多微小直線段來近似，並輸出各段直線插值切削指令(G01)逐步切削。由於五軸加工可能包含線性軸及旋轉軸同動，因此刀具切削點之真正移動速率通常和程式指令的進給率設定值不同，並且隨著各程式段指令各軸的改變量的條件而不同，使得刀具沿切削路徑切削過程其實際進給率會變動不一。本文針對五軸加工進給率穩定化提出分析及調整方法。首先依據CAD/CAM系統輸出的五軸加工NC程式五軸座標資料逐一分析其切削的進給速率，接著換算各程式段欲達到理想進給速率下應設定的進給率值，最後重排及輸出新修改具有理想進給率設定值之五軸加工程式。同時本文方法亦能準確估算程式加工時間。經由實例驗證結果，證實本文方法確實可行。
並列摘要
Computer numerical control (CNC) 5-axis machine equipped additionally with two rotary axes as well as three ordinary linear axes has been widely used in complex parts fabrication such as impeller or cam machining. By using the machine, the workpiece holding or repositioning can be evidently simplified; therefore, the workpiece re-clamping error can also be minimized and the machining efficiency and part accuracy will be enhanced. CAD/CAM system generally divides the tool path curve into many short linear segments and successively generates NC blocks for each linear interpolated cutting command (G01) to approximate 3-axis or 5-axis curve path machining. In 5-axis machining, the linear interpolated cutting motion may be included both linear axis and rotary axis simultaneously so that the real feed rates of the tool tip are not equal to the preset feed rate. Moreover, the real feed rates fluctuate continuously according to the move increment condition of each NC block. In this paper, we propose a method to modify the feed rate setting in each 5-axis NC block for optimizing or stabilizing real tool feed rates. First, use the move information of each 5-axis NC block (generated by CAD/CAM system) to compute its original feed rate. Second, modify feed rate setting referred to the original feed rate for each NC block to make the real feed rate of the tool tip coincide with that of ideal feed rate. Finally, rearrange and output the new modified 5-axis NC program with optimized feed rate setting. In addition, the proposed method can also predict machining time accurately for the part program running. Practical tests by present method were carried out on a CNC 5-axis machining center. The result reveals that the proposed method is applicable.