Page 161 - Modular design for machine tools

Description of Machine Tools 121

identical with those related to the form-generating function, automatic
tool changer, and automatic work changer. As can be readily seen,
Khomyakov and Davydov tried to amalgamate the functional descrip-
tion with the structural description to enhance the design methodology
for the machine tool. Importantly, the earlier achievement performed
within the U.S.S.R. has been finally compiled into a book written by
Reshetov and Portman [12].
To this end, it emphasizes that the research into the functional
description was completed in the mid-1980s, apart from that of Iwata
and Sugimura. Figure 3-6 shows the basic coordinate systems used
to describe the machine tool and a description example proposed by
them [13, 14]. Because of their focus on the application of the functional
description to automatic process planning, their method is more logi-
cal than those mentioned above. One noteworthy aspect is, further-
more, the incorporation of the shape of the cutting edge into the
form-generating movement, where the geometry of the cutting edge
can be defined in a perpendicular plane to the direction of the cutting
motion. Importantly, the form-generating function is affected by not
only the movement function of the machine tool, but also the tool geom-
etry to a larger extent, as can be exemplified by the gang or monolithic
formed cutting tool. They have thus conceptualized the form-generating
movement by a sweep action of the cutting tool, where the principal cut-
ting movement can produce the form entity, which becomes a geomet-
ric form by the travel of the cutting tool within a three-dimensional
space. A characteristic feature is to classify the form entity into the
three types shown in Fig. 3- 7.
To deepen the related knowledge, an interesting trial performed by
Yoshikawa [15] will quickly be reviewed. He tried to represent the
machine and its units with the bond graph, so that the machine relia-
bility could be analyzed. In the bond graph representation, e.g., the geo-
metric connecting relation of parts within a gearbox can be depicted as
in Fig. 3-8, where 8 parts and 11 contracts among them are the nodes
and branches, respectively. This bond graph can be regarded as a func-
tional description containing valuable information. For example, there
are three kinds of branches, i.e., those for transmitting motion and/or
signal, for constraining the freedom of motion, and for fixing; and the
compound-connectivity graph and the functional path can be produced
from the “part-connectivity graph” by choosing the adequate branch. In
due course, we use the concept of functional paths to discuss the struc-
tural reliability. In contrast, the bond graph was produced without con-
sidering the FOF, and both the path and the subpath are not defined
absolutely, but are determined by the designer’s arbitrary choice. As a
result, there remains something uncertain to determine the path.