MODELING OF HIGH SPEED SPINDLES & THEIR STATIC AND DYNAMIC ANALYSIS

Abstract

High speed spindle offers high quality surface finish and elevated production rate since it rotates on rotational speed at and above 10, 000 rpm, hence popularly used in aerospace industries. This dissertation work deals with the high speed spindle of a lathe. The stiffness of the system has been the motivating factor to use high speed spindle to increase production rate. In this report, the problem areas with various design and analysis requirements & constraints are discussed in detail. The important considerations such as rotational speed, stiffness, deflection and hence control on runout of HSS are discussed in detail. On the basis of detailed literature review a spindle bearing system is adopted for this application. Unlike normal spindles, High speed spindle works on the integral motor as a source of power. Keeping in view, the cutting forces and self weight, HSS is designed. The construction and working of the proposed HSS is discussed in detail. Mathematical formulation of the complete system has been developed for the case of bending, torsion and thrust loading considering the design and process parameters by using fundamental laws of mechanics. Finite elemental model of HSS has been developed in a commercial software ABAQUS and analysis in has been carried out with the objective of determining stresses and deflections. The various forces acting on the system and hence stresses developed in the HSS are of compound nature. On the basis of geometric construction, adopting various degrees of simplifications a mathematical model is developed to describe behavior of the system. The spring and damping characteristics depend on the material properties. The developed governing equation of the HSS is a second order ordinary differential equation. It is solved by numerical integration technique using MA TLAB/SIMUL INK tool to obtain the plots of displacement, velocity and acceleration of the mass versus time. The purpose of the simulation is to study the systems responses and check them with the acceptable limits of displacement. Three different boundary conditions are implemented to simulate the mathematical model viz, no load condition, step excitation by the tool and step excitation by induction motor. Using the mathematical model the influence of these key parameters on the overall performance of the system is studied.