本文選題：過渡曲面 + 平頭立銑刀��； 參考：《華中科技大學(xué)》2015年碩士論文

【摘要】：在汽車車身、航空航天器及各種成形模具的設(shè)計和切削加工中,經(jīng)常涉及到過渡曲面,作為兩個母曲面之間光順連接的曲面,對于提高產(chǎn)品外表的美觀,增強零件的剛度,改善模具的沖壓性能,避免沖壓件起皺,具有十分重要的作用。通過深入分析和研究,目前只能采用球頭銑刀或者成型刀來加工過渡曲面。球頭銑刀在切削加工中,切削效率低,加工表面質(zhì)量差,多次的往返加工影響過渡曲面的光順性;而成型刀只能加工固定曲率的過渡曲面,不同曲率過渡曲面需要制作不同形狀成型刀。對于非固定曲率的過渡曲面,只能采用球頭銑刀加工,給實際生產(chǎn)帶來極大不便。平頭立銑刀通過偏轉(zhuǎn)角度可以獲得較大的有效切削半徑,具有切削效率高,加工表面光順等特點。針對球頭銑刀或者成型刀在過渡曲面加工中存在的問題,本文提出了一種采用平頭立銑刀沿過渡曲面脊線的縱向加工的方法。該方法以刀具的接觸點為參照,基于空間過渡曲面在不同位置的曲率變化趨勢,偏轉(zhuǎn)平頭立銑刀沿過渡曲面脊線的縱向和法向角度,利用平頭立銑刀隨著偏轉(zhuǎn)角減小而有效切削半徑增大的特點,在實際切削過程中盡量減小偏轉(zhuǎn)角,增大有效切削半徑,同時保證不發(fā)生刀具干涉。每個刀位點計算,通過建立過渡曲面脊線的空間模型,按照曲率匹配原則確定刀具初始位置,基于網(wǎng)格劃分法和距離極值法,判斷刀具是否發(fā)生過切干涉和碰撞干涉,根據(jù)刀具的干涉檢查結(jié)果實時修正刀具的偏轉(zhuǎn)角度,以調(diào)整刀具切削姿態(tài)和過渡曲面之間的位置關(guān)系,從而獲得無干涉刀位點。如此類推,可以求得整張過渡曲面的無干涉刀具軌跡。然后,基于傳統(tǒng)等殘留高度刀具軌跡生成方法建立刀具軌跡的優(yōu)化模型,對所生成的無干涉刀具軌跡進行光順化處理,得到滿足光順約束條件的刀位點,最終擬合得到具有等殘差光順的無干涉刀具軌跡。通過仿真分析,本文提出的方法能夠?qū)崿F(xiàn)平頭立銑刀沿過渡曲面脊線的縱向的無干涉切削加工,加工后表面殘留高度較為均勻,波動較小。與球頭銑刀比較,不僅切削加工效率高,而且表面光順性好,可望在未來過渡曲面編程中得到實際應(yīng)用驗證。
[Abstract]:In the design and cutting of automobile body, aeronautical spacecraft and various forming dies, the transition surface is often involved. As a smooth connection surface between two parent surfaces, it can improve the appearance of the product and enhance the rigidity of the parts.It is very important to improve the stamping performance of die and avoid the wrinkle of stamping parts.Through deep analysis and research, only ball-end milling cutter or shaping cutter can be used to process the transition surface.In the cutting process of ball end milling cutter, the cutting efficiency is low, the quality of the machining surface is poor, and the fairing of the transition surface is affected by many round trips, while the shaping cutter can only process the transition surface with fixed curvature.The transition surface with different curvature needs to be made with different shapes.For the non-fixed curvature transition surface, only the ball end milling cutter can be used, which brings great inconvenience to the actual production.The flat end milling cutter can obtain a large effective cutting radius by deflection angle, which has the characteristics of high cutting efficiency and smooth machining surface.Aiming at the problems of ball end milling cutter or shaping cutter in the machining of transition surface, a method of longitudinal machining with flat end milling cutter along the ridge of transition surface is proposed in this paper.This method takes the contact point of the tool as the reference, and based on the curvature change trend of the spatial transition surface in different positions, the deflection end milling cutter along the longitudinal and normal angles of the ridge of the transition surface.Based on the feature that the cutting radius of flat end milling cutter increases with the decrease of deflection angle, the deflection angle is reduced and the effective cutting radius is increased in the actual cutting process, and the tool interference is guaranteed at the same time.According to the principle of curvature matching, the initial position of the tool is determined by establishing the spatial model of the ridge line of the transition surface. Based on the meshing method and the distance extremum method, whether or not the tool has overcut interference and collision interference is judged.According to the interference inspection results of the tool, the deflection angle of the tool can be adjusted in real time to adjust the position relationship between the cutting attitude and the transition surface, so as to obtain the position of the non-interference cutter.By analogy, the non-interference tool path of the whole transition surface can be obtained.Then, based on the traditional equal height tool path generation method, the optimization model of tool path is established, and the tool locus satisfying the fairing constraint condition is obtained by smoothing the generated non-interference tool path.Finally, the non-interference tool path with equal residual smoothing is obtained by fitting.Through simulation and analysis, the method proposed in this paper can realize the longitudinal non-interference cutting of flat end milling cutter along the ridge of transition curved surface, and the residual height of the surface after machining is more uniform and the fluctuation is relatively small.Compared with the ball end milling cutter, not only the cutting efficiency is high, but also the surface smoothness is good, which is expected to be verified by practical application in the future transition surface programming.
【學(xué)位授予單位】：華中科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TG54

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