Page 219 - Modular design for machine tools

Basic Knowledge of Machine Tool Joints 179

machine tool. The corresponding joints are, e.g., the slideway (guideway)
and main spindle bearing.
2. To provide the flexibility in both the functionality and performance to
the machine tool, i.e., application of the modular design concept so as
to respond to multifarious machining requirements of the customer.
In the modular design of unit type, a machine tool structure consists
of a group of units, and a root cause of its difficulties lies, in princi-
ple, in the connecting method of both units. At present, the modular
design prevails especially in the production of conventional MC and
TC, in other words, NC machine tools of conventional type (refer to
Chap. 1). A corresponding representative is, e.g., the bolted joint.
3. To improve the dynamic stiffness of a machine tool. Obviously, it is
desirable to provide higher damping while maintaining the higher
static stiffness. A representative is the damping joint for the welded
structure, which was contrived in the United States and widely
employed by Japanese machine tool manufacturers [8].
4. For the ease of manufacture, e.g., ease of machining and assembly of
units and parts, convenience for component allocation, embodiment
of power transmission mechanism, electrical and electronic equip-
ment within a structure, and so on. A representative for fulfilling
these requirements is the bolted joint.
5. To simplify the casting procedure, e.g., as a convenience for the sep-
aration of wooden pattern, removal of sand from the structural body
after casting (fettling), and so on.
6. For the allocation and adjustment of the additional components, e.g.,
hardened steel strip guideway bolted on the welded or bonded on con-
crete structure.
7. To solve the transportation troubles in the large-size machine tool.
We must furthermore keep in mind that these requirements from
design and manufacturing originally suggested in the era of the tradi-
tional machine tool. In due course, such requirements have been mod-
ernized with the advent of NC machine tools, aiming at full availability
for the machine tool in the year 2000 and beyond. In addition, when we
change the viewpoint from hardware to software, at succeeding issue is
related to the CAD and CAE (computer aided engineering) for the
machine tool design. Most machine tool manufacturers worldwide now
employ CAE, also known as digital engineering, by emphasizing the
computation of the static and dynamic stiffness, and thermal deforma-
tion at the stage of the basic layout or embodiment design. In other
words, the CAE is now one of the effective tools used to estimate the per-
formance of a machine tool at the design stage along with the assessment