The Technique Research On Surface Quality Prediction In Root Milling

The turbine rotor is a dynamic part of the turbine. The machiningquality of rotor is good or bad will have a direct impact on the performanceof the entire turbine. The rotor roots processing is the most critical anddifficult part of the rotor machining. Based on the shape complexity of firtree roots of steam turbine and materials unworkability of the rotor, fir treeroots surface quality prediction was researched.There are many types of steam turbine rotor fir tree roots which millingprocess is the most complex. The fir tree roots milling is often usedV-shaped milling process: the V-grooves milling-the bottom of the straightgrooves milling-bottom line milling-fir tree line Finishing-the precisionmilling of fir tree line. Many factors affect the surface roughness of fir treeroots milling process: the geometrical factors, physical factors and processfactors. Major influencing factors to consider in the text of the spindlespeed, feed per revolution volume and tool geometry. The support vectormachine was used as the theoretical basis of the modeling of surfaceroughness prediction in this article. Taking into account the vibrationacceleration was larger in the fir tree roots finishing milling process.Therefore the milling force model and dynamic model were derived. Basedon the two models, the surface roughness prediction model was derived.Through the fir tree roots milling experiments on rotor material30Cr2Ni4MoV, the mean square error is0.0058was given between thesurface roughness prediction and the measured values. The study found thatthe surface roughness will be increased when the tool angle of5°to7°, butthe surface roughness will be decreased when the tool angle of7°to10°.When the spindle speed is selected in the interval as (9000r/min~11000r/min) or (13500r/min~14500r/min) or (17000r/min~18500r/min),the surface roughness value was floated in the range (0.9μm~1.4μm), thesurface roughness of the indicator1.6μm was guaranteed. Through the studyof this subject, it is important guiding significance to improve the surfacequality of the rotor roots and the choice of cutting parameters.