Abstract
Upcoming machine tools need to be extremely efficient systems to maintain the needed intellectual performance and stability. The spindle tool system is necessary to optimize which enhances the rigidity of the spindle and in turn produces the cutting stability with higher productivity. Prediction of the dynamic behavior at spindle tool tip is therefore an important criterion for assessing the machining stability of a machine tool at design stage. In this work, a realistic dynamic high-speed spindle /milling tool holder/ tool system model is elaborated on the basis of rotor dynamics predictions. The integrated spindle tool system in analyzed with the Timoshenko beam theory by including the effects of shear and rotary deformation effects. Using the frequency response at the tool tip the corresponding stability lobe diagrams are plotted for the vertical end mill system. Furthermore an optimization study is carried out at design stage for the bearing system and the rotor positions for maximizing the chatter vibration free cutting operation at the desired depth of cuts with precise rotational speeds.It is markedly found that the first mode of vibration had a large impact on the dynamic stability of the system. The parametric studies are conducted such as tool overhang and bearing span and the influence of these on the system dynamics are identified and the corresponding stability lobe diagrams are plotted. It is evidently found that the second mode of the frequency response has critically affected the bearing span and competing lobes are identified. These results are assisted to design a spindle bearing system at the desired machining conditions. A neural network based observer is designed based on the simulation resultsto predict optimum design parameter values.
Highlights
In recent years, the technical advancement of high speed machining (HSM) has been significant
The frequency response is evaluated at the tool tip by the considering the centrifugal effect and the dynamics of bearings at the rear and front position at spindle speed of 5000 rpm
Using MATLAB programming the responses are arrived with the mountings of the bearings calculation, the responses are shown in Figure.3 and it is observed that the peak frequency is 2250Hz
Summary
The technical advancement of high speed machining (HSM) has been significant. The machining at higher axial depths of cuts and spindles will achieve high material removal speeds (MRR). In order to explore their effect on the natural frequencies of the spindle mechanism, a design sensitivity analysis of these eight design parameters is performed based on an applied finite element process model. An updated FRF model is adapted to evaluate the worst spindle speeds and the critical limiting axial depth of cut in explicit, theoretical formulas for a two degree of freedom milling method of planar isotropic dynamics. Tool-tip FRFs are calculated to efficiently plot the stability lobe diagrams using the known radial immersion depths in the high-speed end-mill machining process for this spindle bearing system. The organization of the paper is as follows: Section-2 give details of the spindle-bearing unit and finite element modelling and Section-3 discuss the dynamics and cutting forces of the machining process during the end-milling operation.
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