Page 100 - Modular design for machine tools

64 Modular Design Guide and Machine Tools Description

2.1 Four Principles and Further
Related Subjects
In this section, the four principles are discussed in detail to quickly
understand what basic engineering knowledge is used in the applica-
tion of modular design to the machine tool. In fact, the four principles
are basically worth following even now. It is very important, however,
to be aware of the changing trends of modular design resulting from the
enlargement and enrichment of the application areas. For example, the
modular design concept must be modernized so as to be compatible with
the production environments at present and in the near future. Thus,
in this section we furthermore touch on the new variants of the modu-
lar design concept in the year 2000 and beyond.
Principle of separation. The principle of separation is in closer relation
to how to determine the module, and of the four principles, this principle
has the greatest difficulty being sublimated to a preferable technology.
In fact, the basic modules have been determined so far by using the
trial-and-error method. The principle of separation can thus be defined
as follows.

A module is allowed to have only a specified function and/or structural con-
figuration in full consideration of the following.
1. The user does not mind whether the machine is designed using the
modular principle or not, apart from machines of customer- oriented
type, and thus the module must have the least function and con-
figuration acceptable, but not be overspecified.
2. The module must have satisfactory stiffness as well as high joint
stiffness.
3. The machining accuracy of the module should be within allowable
tolerances to achieve the required assembly accuracy under any
joint conditions.
In this context, the crucial issues are how to disintegrate a machine
tool as a whole into the proper number of modules and how to determine
a group of standardized modules according to the design purpose. For
instance, the machining space should be investigated in the unit con-
struction of an NC turning machine such as that of Feldmann [2].
Figure 2-1(a) and (b) shows the frequency distribution of the traveling
ranges of the carriage and cross slide, as well as the structural config-
uration and rotating axis of the turret head of the NC turning machine.
It is obvious that the cross slide travels mainly between 300 and 600 mm
notwithstanding the type of machine, and the turret head of disk type
is protruded. Importantly, we must be aware that the machining space
is in good agreement with the work spectrum, which must be determined