Modal Analysis of a Spindle of Computer Numeric Controlled Milling Machine

Abstract

Computer Numerical Controlled (CNC) machine for milling can accomplice the purposes of drilling and turning. Machine tools is one of many aspects that can possibly impact the quality of the finishing product of a machining. Exploration on the stability and identification of the vibration that occurred in the spindle of CNC machine is carried out. A spindle comprises of a motor, a taper for holding tools, and a shaft that holds together all the different components. Spindles rotate on an axis, which gets input on movement from the associated CNC controller. Modal analysis was carried out for the model of spindle. Rest of the cases assessment were done against this model. Total of eight cases formed by additional stiffeners varying position and figures. The first case was of spindle model only. This study uses the outcome of vibration obtained to support by performing modal analysis while varying the stiffeners position and shape. The frequency analysis helps us to explore effect of stiffeners in vibration. The input parameters were kept same so that any result observed would be because of the addition of stiffeners only. One case each for rectangular and circular shaped stiffeners applied near tool holder was created. The first natural frequency for spindle only was obtained as 290.28 Hz. Maximum deformation was 4.04. Application of stiffeners showed reduced modal amplitude. Combination of rectangular and circular shaped stiffeners were applied together and in addition with the stiffeners in groove to create four more cases. The modal analysis for all these cases was performed to obtain mode frequency and deformation shapes for the spindle. The deformation shape was found similar in eight cases. Addition of stiffeners has no significant effect on shifting of mode shape and. Addition of stiffeners however, lowers amplitude of modal displacement to reduce vibration on tool holder. The shape of stiffeners has no noteworthy effect on vibration. The frequency and deformation on model of spindle with rectangular shaped stiffeners and circular shaped stiffeners are nearly identical.