Page 58 - Modular design for machine tools

Basic Knowledge: What Is the Modular Design? 29

had not received the devastation due to the war. More specifically, the
production facilities had to be reinforced so that the production volume
of cars increased with the keen economic benefits. In this task, a facing
problem was how to rationalize the machining capability of the car
parts, e.g., cylinder head, engine block, axle housing, and mission gear-
box. Intuitively, a dominant hindrance derived from the mass produc-
tion, for which the highly automatized machining system was suitable.
For example, the work was transferred automatically among the
machining stations and processed again automatically its corresponding
portions at each station, maintaining always its preparatory setting
condition. As can be readily seen, such a facility has less flexibility in
machining capability instead of higher automatization, resulting in the
requirement of the large amount of renewal cost, when the model change
of car is made to reinforce the marketability.
In due course, U.S. car manufacturers proposed a concept of machine
tool construction with standardized units, actually that of BBS, to enable
the interchange of the unit with on-site manner, i.e., user-oriented mod-
ification at user’s factory, and to minimize the renewal cost of the
machining facilities. The car manufacturer then carried out the research
and development necessary to make the concept a reality in cooperation
with the machine tool manufacturer. As a result, the TL was realized,
which was, in principle, classified as the line type, i.e., that of TL itself,
and rotary indexing type including those of star-wing and trunnion
types, depending on the machining requirements and size of parts to be
processed. As planned, the car manufacturer gained considerable eco-
nomic advantage even in carrying out the mass production and fre-
quent change of the car model.
In the 1960s, Cross and Kingsbury Machine Tool were the leading
manufacturers of the TL and rotary indexing machine across the world,
and Figs. 1-18 and 1-19 show the typical TL and rotary indexing
machine. From these, we can observe the basic entities (units) to con-
sist of the TL and rotary indexing machine, e.g., spindle head, gang
drilling head, power unit, feed unit, base, and adapter. In both the TL
and the rotary indexing machine, the basic unit complex is called the
station, which is actually the special-purpose machine tool. Importantly,
the TL is for mass production of the specified work and can be defined
as a production facility consisting of a group of the stations and related
equipment, such as work turnover device, washing station, and meas-
urement stand. In addition, the work is in line flow–like transferred
from station to station with the constant tact time (a kind of cycle time:
work-in-station time in intermittent transfer line). In contrast, the rotary
indexing machine can be interpreted as a variant of the TL, where the
work is in circular flow-like transferred from station to station. In due
course, each station can process the work in accordance with the