Keywords: optimization, machine tools, finite elements method, genetic algorithms.

Experience has shown that machine tools manufacturers very often create new designs on the basis of solutions that are old and proven yet not always optimal. A new approach to the design of the bodies of machine tools for high speed cutting (HSC) is necessary. So far, the main criterion in machine tool body design has been the required static stiffness. In the case of HSC machine tools, for which speed and accelerations are considerably higher, beside the static stiffness criteria, there are other equally important facts to be considered, such as: dynamical criteria and the minimization of the mass of movable assemblies. Therefore, a designer of machine tools bodies an optimization tool for the mass of the body and stiffness indices. The analysis of the stiffness of machine tool bodies must be conducted by means of numerical methods (finite element method) because of their complex shapes. A typical body of a machine tool is characterised by dozens of variables, including the thickness of walls and ribs, geometrical dimensions of the ribs, their number and position. Accordingly, the optimization of such body compels the use of effective algorithms, for example, those that apply artificial intelligence methods, including genetic algorithms (GA).

The scope of the paper is the classification of machine tools bodies from the point of view of optimization. Attention was paid to economical and practical aspect.

The bodies selected for optimization are described, with the corresponding calculation options and boundary conditions. The bodies of heavy machine tools, such as a vertical lathe, planer mill and the bodies of middle-sized milling machine tool centre with slidable column were taken into account [1,2,3,4].

Models of the classified machine tools are described in terms of the finite element method. The results of initial analyses are presented and will be used as the reference values for the optimization of selected machine tool bodies. The preliminary tests involved the estimation of the static stiffness and free vibrations frequency. In the paper the results of the initial optimization of selected bodies for milling machine tool centres based on the designer's intuition and initial finite element analyses were also presented. This complex approach towards simulation research makes it possible to formulate some general conclusions.

1

Design documentation of HSM 180 Planer Mill, Rafamet S.A. 2004.

2

Design documentation of KCI series Vertical Lathe, Rafamet S.A. 2001.

3

Design documentation of The Milling Machine Tools Centre with Slideable Column, CBKO Pruszków, 2006.

4

Design documentation for FB 125N Cogifer II Planer Mill, DTI, 2008.

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