Cutting Deformation Control Method On Large Rotor Semi-closed Thin-walled Deep Slot

The rotor is one critical component of a large power generator equipment, whosemanufactured quality has great impact on the generator’s operation conditions. In case of1100MW four pole generator rotor, it has the low stiffness as whose semi-closed coil slotdepth reaches up to218mm and slot boot thickness is only15mm and this structuralcharacteristics lead to difficult to be cut off by the machining deformation. Thus how tocontrol and reduce the deformation during the process of the semi-closed slot is the key toimprove the rotor running accuracy and ensure generator’s service performance.In the semi-closed coil slot machining, it happen deformation. The semi-closed coilslot’s mouth deformations reach up to0.52mm. Based on machining process analysis ofthe semi-closed slot and open slot, two important reasons are identified to cause thesemi-closed slot’s cutting deformation. One is due to the cutting force, and the othercomes from the residual stress. The cutting forces of semi-closed type A、type B、type Cslot are634.4N、506.8N、785.9N respectively, according to the theoretical calculation ofthe HSS forming milling cutter finish-milling. By means of using the auxiliary supporttools during cutting the semi-closed slot and making the related measurement, it is aneffective method to control the cutting deformation of semi-closed slot. Auxiliary supporttools can be used for the lower stiffness slot, then they are placed them at the slot’s mouthposition and uniformly distribute along the slot’s axial direction. The finish millingdeformation can be calculated using finite element analysis, which provide necessary datafor the reverse compensation amount of the auxiliary support tools. The results show thatthe reverse compensation reasonable ranges for the auxiliary support tools. Therequirement tolerance range of0～0.2mm can be achieved using the reverse compensationduring machining and after releasing the residual stress.