Page 215 - Modular design for machine tools

Chapter
5

Basic Knowledge of
Machine Tool Joints

Professor Kienzle is credited with being the first to conduct prelimi-
nary research into the machine tool joint, i.e., comparative research
into the damping of the steel welded to cast bed structures, in 1939 [1].
On that occasion, Kienzle implied that the important role of the machine
tool joint might be to increase the damping capacity of a machine tool
as a whole; however, up to the beginning of the 1970s engineers designed
the machine tool by paying special attention to only the body struc-
tures.
In fact, there have been many researches into the problem of two
elastic bodies in contact, such as Hertz’s theory concerning the design
of the rolling bearing and stamping problem. Importantly, these earlier
works have been based on an assumption: The joint surface has no rough-
ness, waviness, and flatness deviation. This assumption means that
the joint is topographically perfect and has an ideal surface, but actu-
ally we cannot obtain such a joint surface even when producing it by the
utmost leading-edge and ultraprecision processing methods. In short,
nearly all the theories of elasticity available at present can deal with the
problem of the monolithic elastic body, i.e., elastic body without any
joints. Thus, the dire necessity is to establish a theory for the design of
machine tool joints, in which the topography of the joint surface has
greater influence on the behavior of two elastic bodies in contact.
Other problems of two surfaces in contact are (1) the Mindlin slip
theory at microseizure contact points under shear load and (2) the real
contact area between two surfaces, proposed by Bowden and Tabor.
These are topics in tribology engineering and in certain relation to the
machine tool joint. In retrospect, the wear and friction of the guideway,
one of the tribology engineering problems, have been a major focus in
175
Copyright © 2008 by The McGraw-Hill Companies, Inc. Click here for terms of use.