Page 221 - Modular design for machine tools

Basic Knowledge of Machine Tool Joints 181

dashpot (damping capacity of joint). In principle, a main spindle system
can be replaced with a mathematical model of an elastic beam sup-
ported by both the spring and the dashpot at two or three points. In fact,
the dynamic performance of the main spindle can be simulated using
this mathematical model and the spring and dashpot as variables. In
time, the basic necessity is to correctly determine the spring constant
and damping coefficient together with the static and dynamic boundary
conditions of the spindle system. These variables are, however, still dif-
ficult to quantify correctly even when we are using the knowledge
obtained so far within the machine tool joint sphere.
In short, the body structure of a machine tool consists of a considerable
number of structural body components and their interfaces, i.e., joints. The
joint itself can be regarded as one of the structural body components,
exerting considerable influence on the static, dynamic, and thermal behav-
ior of a machine tool as a whole. Thus, we should design the functional-
ity and structural configuration of the joint to provide the preferable
performance to a machine tool. In addition, we must pay special atten-
tion to the joint when machining it and assembling a machine. As a result,
we often refer to the design and manufacturing problems related to the
joint as the problems of machine tool joint. At present, this problem sphere
encompasses those problems related to chucking, tooling, jig, fixtures, and
so on, although originally the machine tool joint was discussed in the
design work on the slideway, bolted joint, and foundation.
Within a machine tool engineering context, it is again worth sug-
gesting that modular design, especially the principle of connection is in
the closest relation to the problems of the machine tool joint. A dire
necessity is thus to deepen our understanding of the essential features
of the machine tool joint, simultaneously crystallizing the keen role of
the modular concept in machine tool design.

5.1 Classification of Machine Tool Joints
In a machine tool, there are various kinds of joints, for instance, the
bolted joint, guideway, joint between the concrete foundation and the lev-
eling block, taper connection between the cutting tool and the spindle
hole, press fitting of the outer race of bearing to the housing, and so on.
These joints appear to be very different from one another in their struc-
tural configurations; however, these differences depend only upon their
required functions to be performed in the machine tool structure. More
specifically, the basic structural configuration of various joints is two flat
surfaces in contact, i.e., a simple flat joint, although a handful of rep-
resentative joints can be observed within a machine tool as a whole.
In contrast, it is necessary to classify these various joints as suitable
for the structural design of the machine tool. In the classification of the