螺旋式真空泵(screw vacuum pump)係利用兩嚙合螺桿轉子間封閉齒腔進行空氣抽送，使工作空間達到所需真空度，其廣泛運用於現今之半導體及化學、化工產業，真空泵轉子上常設計有一提升密封性減少洩漏之擺線(cycloid)輪廓，造成在加工上的困難。有鑑於此，本研究應用一種新型加工技術「旋風式銑削(whirl milling)」於真空泵螺桿轉子加工。本文建立旋風式銑削泛用與CNC加工數學模型，並推導刀具切削面、刀盤與刀條設計、及各加工軸之運動方程式；之後，透過數值範例程式計算獲得加工模擬轉子齒面，再與設計轉子齒面計算齒面誤差後可證實數學模型之正確性；此外，本研究亦應用CAM軟體建立多軸CNC旋風式銑削加工機台模型、規劃加工碼並進行螺桿轉子切削模擬，以測試本加工方法之可行性；最後，將本文加工方法使用於多種真空泵轉子上驗證其廣泛的適用性。 ;A screw vacuum pump works to achieve required vacuum degree by means of two meshing screw rotors, which transmit gas enclosed in screw grooves and a housing. It is widely used in today′s semiconductor, chemical, and chemical industries. Cycloids are usually adopted in rotor profile design to enhance airtightness; however, this design forms a concave rotor profile and increase machining difficulty. In view of this, this study attempts to extensively apply whirl milling to more efficiently cut the screw rotor with cycloid sections. Whirl milling has the advantage of high efficiency when processing long screws with single helix and short lead. Two relative motion coordinate systems are established respectively for a universal machine and a CNC machine according to the relative motion relationship, that a ring-shape cutter body containing inside cutters bias mills the screw rotor in the axial direction with a high rotational speed to obtain cutting rake profiles and motion equations of machining axes. The cutting simulation is practiced in the developed program to attain the simulated screw surface, which is used for checking the correctness of the established mathematical model. In addition, a virtual CNC milling machine is constructed in VERICUT software and used to verify the screw rotor milling process with the planned NC code. Also, the proposed method is applied to different types of vacuum pump rotors to verify its wide applicability.
