Optimum Design of Spindle-Bearing Systems
Dumitru D. Nicoara
Transilvania University of Brasov, Brasov, ROMANIA, [email protected]
Abstract: In this paper we proposed several optimization models for spindle-bearing systems. The goal is to find out the
position of the bearings, the diameters of the spindle (different diameters for several segments of the spindle) in order to
maximize dynamic stiffness (minimize receptance), i.e. the diminishing of the vibrations. Some constraints are imposed: the
distances between bearings, different diameters for several segments of the spindle, etc.
The method is very useful for the design engineers from the very beginning of the design, offering to the designer the optimal
values of the parameters.
Keywords: spindle, bearing, finite element, optimization, dynamic stiffness
The static and dynamic behavior of machine tools is influenced significantly by the design of the spindle and its
bearings. The distance between the bearings and bearing preload has considerable influence on the stiffness of
the spindle. It is often important to consider the dynamic behavior of a spindle before establishing an optimum
bearing span. In this paper we propose an external (passive) optimization model for spindle-bearings systems.
The goal being the diminishing the vibrations by the maximizing of the dynamic stiffness, i.e. by minimizing of
the receptance. The paper proposes a bearing spacing optimization strategy. The spindle is analyzed by a
proposed Finite Element Method (FEM) algorithm based on Timoshenko beam elements.
Therefore, the code computer optimization program in MATLAB is obtained by the coupling of the FEM with
the nonlinear optimization methods with constraints
The proposed system is demonstrated against a commercially existing machine tool (Mori Seiki SH-403). The
spindle has a motorized transmission with oil–air type lubrication with four bearings at the front and one at the
rear. The maximum spindle speed is 20,000 rpm and the power and torque properties of the spindle motor are set
from the data shown in .
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