Page 155 - Modular design for machine tools

Description of Machine Tools 115

circle) [2]. His suggestion did not catch on, and we have used the term
FOF up to now. It appears that the FOF can be absolutely defined by
the well-known proposal made by Schlesinger [3] in the 1930s.
It is, in principle, desirable that the machine tool be represented with
only one absolute description, or that the functional description be in
one-to-one relation to the structural description, and vice versa. Such a
requirement can be fulfilled in the case of the part and functional com-
plex, but is far from being fulfilled in the case of the machine as a whole,
i.e., entity belonging to higher layer within the hierarchical structure
of a product. In fact, the structural entity of higher layer has complicated
properties in both the functional and structural aspects. In the design
procedure, it is thus imperative for the time being that a functional
description may accordingly correspond with various structural descrip-
tions, although a structural description is in one-to-one relation with a
functional description.

3.2 Details of Functional Description
The functional description can be defined as a machine tool representa-
tion method with the leading traveling and rotational movements or
form-generating movement, where the latter is a chosen combination of
the former to especially represent the form-generating functions possible.
As already mentioned, Stau proposed the preliminary idea of functional
description, and later Vragov of the U.S.S.R. publicized a noteworthy
description method in 1972 [4]. He suggested that the machine tool struc-
ture can logically be represented with the AND and OR connection
between both structural entities, resulting in structural formulas based
on the logic algebra and multiple-factor theory. Figure 3-1 shows some
examples of the description, and in the following, the description is
stated in steps.

1. Coordinates are determined by distinguishing the linear and rota-
tional movements and identifying the leading and auxiliary move-
ments, provided that the X axis is for horizontal longitudinal
movement and the Z axis is parallel to the main spindle axis.
Leading movements: Linear X, Y , and Z
Rotational A, B, and C
Auxiliary movements: Linear U, V, and W
Rotational D and E
2. Affix the subscripts h and v to Y and Z to distinguish the horizontal
and vertical movements.
3. Represent stationary units (modules) with “O” and moving units with
coordinates determined in step 1. In principle, the machine tool can
be represented with the symbolized combination of the rectilinear