Page 38 - Modular design for machine tools

10 Modular Design Guide and Machine Tools Description

machining function consists of the head changers of modular type called
Variocenter. Importantly, there are two types of FTL depending on the
basic module and flexibility of the transfer line of asynchronous type. In
the FTL of simple line flow type shown in Fig. 1-6(a), the basic module is
that of Variocenter itself, resulting in less flexibility in the work transfer
function, whereas in another FTL shown in Fig. 1-6(b) the basic module
is of FMC to enhance the flexibility in both the machining and transfer
functions. More specifically, the FMC can be formed from the Variocenters
of various types in addition to having both the subtransfer line, i.e., trans-
fer shuttle conveyor, and the work waiting station, which are capable of
the leapfroglike work transportation, resulting in greater flexibility in the
transfer function of the system. The FTL in Fig. 1-6(b) has been installed
at Opel to handle the increasing number of engine varieties. In fact, the
kernel of Variocenter is a hexagonal turret having a group of cutting tools
to machine the objective work. The turret and work can be transported
to the machining space by using the overhead crane and the carrier on
the floor, respectively. Thus the system can facilitate drilling, deep hole
drilling, counterboring, reaming, spot facing, tapping, precision milling,
precision facing, and inspection. Then the system is available, for exam-
ple, for the manufacture of cylinder heads and cylinder blocks made of
gray cast iron, high alloy cast iron, and die cast aluminum alloy. According
to the report of Siegfried at the International Symposium on Automotive
Technology and Automation in 1984 held in Milan, 80 percent of the
system can be reused in the event of product changes.
As can be readily seen, flexible manufacturing of the FMC-integrated
type was an eminent contrivance from the modular design viewpoint,
and even in the year 2000 it was the leading system design methodol-
ogy. In due course, the FMS (flexible manufacturing system) of FMC-inte-
grated type was to become a reality by the ZF (Zahnrad Fabrik
Friedrichshafen GmbH), one of the representative mission gearbox man-
ufacturers in Germany, for producing gears on that occasion. In the
case of FMS of ZF make, one of the marked features was that it facili-
tated the inheritance of the craftsmanship by using the job rotation
between the FMS and the traditional factory. This feature leads us later
to an idea of the modular design of culture- and mindset-harmonized
type (see Chap. 2).
These examples may help the reader to imagine what modular design
is to some extent; however, we must discuss these in detail to best use
the modular design. In this chapter, first we give a quick summary to
deepen the reader’s understanding of the essential features and to point
out the advantages and disadvantages of modular design. Next we give
a firsthand view of the long history of modular design by clarifying the
epoch-making events and depicting some representative achievements
made thus far.