Section 13. qxd

computer-integrated manufacturing
(CIM).
This system involves the coordinated participation of computers
in all phases of manufacturing. 
Computer-aided design
combined with
computer-aided manufacturing (CAD/CAM)
results in a much higher pro-
ductivity, better accuracy and efficiency, and reduction in design effort
and prototype development. CIM also involves the management of the
factory, inventory, and labor, and it integrates all these activities, even-
tually leading to untended factories.
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MACHINING PROCESSES AND MACHINE TOOLS
The highest level of sophistication is reached with a 
flexible manufac-
turing system (FMS).
Such a system is made of
manufacturing cells
and an
automatic materials-handling system interfaced with a central computer.
The manufacturing cell is a system in which CNC machines are used to
make a specific part or parts with similar shape. The workstations, i.e.,
several machine tools, are placed around an 
industrial robot
which auto-
matically loads, unloads, and transfers the parts. FMS has the capability
to optimize each step of the total manufacturing operation, resulting in
the highest possible level of efficiency and productivity.
The proper design of 
machine-tool structures
requires analysis of such
factors as form and materials of structures, stresses, weight, and manu-
facturing and performance considerations. The best approach to obtain
the ultimate in machine-tool accuracy is to employ both improvements
in structural stiffness and compensation of deflections by use of special
controls. The C-frame structure has been used extensively in the past
because it provides ready accessibility to the working area of the
machine. With the advent of computer control, the box-type frame with
its considerably improved static stiffness becomes practical since the
need for manual access to the working area is greatly reduced. The use
of a box-type structure with thin walls can provide low weight for a
given stiffness. The light-weight-design principle offers high dynamic
stiffness by providing a high natural frequency of the structure through
combining high static stiffness with low weight rather than through 
the use of large mass. (Dynamic stiffness is the stiffness exhibited by the
system when subjected to dynamic excitation where the elastic, the
damping, and the inertia properties of the structure are involved; it is a
frequency-dependent quantity.)