應用於橢圓車削之新型快速刀具滑台設計

Abstract

本論文的主要目的是以軟體控制靠模數控車床為基礎，針對橢圓截面或橢圓軸，設計出創新的機構式快速刀具滑台來對加工件進行車削加工，實現大行程、高精度之橢圓外形。本論文先建構該快速刀具滑台之數學模型而後分析其運動學，包含曲柄旋轉角度(θ_2)、搖桿的擺動角度(θ_4)、刀具的位移(r_6)、速度(〖Vol〗_c)、加速度(〖Acc〗_c)及急跳度(〖Jerk〗_c)，再以粒子群演算法(Particle Swarm Optimization)來得到當急跳度最小時的最適合連桿尺寸。該快速刀具滑台上結合電子凸輪(Electric Cam)來做刀具軌跡規劃，補償車刀因位移所產生的誤差量。最後本論文以試製機台探討該快速刀具滑台對於橢圓車削後的精度，包括刀具空切模擬橢圓車削與工件的實際橢圓車削。從結果顯示，橢圓率為0.0862(切深小)與0.3965(切深大)，兩者皆以120rpm來進行車削，橢圓率小者所得到之橢圓輪廓精度優於橢圓率大者。由此可知，橢圓車削誤差主要和刀具的最大切深有關，而非主軸轉速。車削量愈多，其橢圓輪廓誤差量就愈大。研究結果顯示本論文所提出之快速刀具滑台在橢圓車削之可行性。

The main purpose of this thesis was to develop an innovative fast tool stage for the ellipse turning based on the CNC lathe machining a shaft with variable ovalities. The mathematical model of the fast tool stage was first developed, then the corresponding kinematics were analyzed, including the crank rotation angle(θ_2), the rocker swing angle(θ_4), the tool feeding displacement(r_6), and the velocity (〖Vol〗_c), acceleration(〖Acc〗_c) and jerk(〖Jerk〗_c). The particle swarm optimization algorithm was employed to synthesize the linkage dimension of the fast tool stage considering the tool feeding jerk being the minimization. Finally, a laboratory built lathe with the fast tool stage combined with an electronic cam was used to implement the ellipse turning. Moreover, the inverse kinematics was solved to plan the trajectory of the tool feeding displacement so that the caused machining errors were compensated. The elliptical machining accuracy for the fast tool stage was further discussed and analyzed through both the elliptical turning simulation and the actual elliptical turning on workpiece. The results show that the elliptical contour accuracy obtained with small elliptic ratio is better than that of the larger elliptic ratio. It implies that the elliptical turning error is mainly related to the maximum cutting depth of the tool, not the spindle speed. The more the feeding amount, the larger the elliptical contour error. It is seen that our developed fast tool stage in this paper is feasible on elliptical turning.