Page 249 - Modular design for machine tools

Basic Knowledge of Machine Tool Joints 209

1. Use of logarithmic curved roller to the roller bearing, in order to real-
ize the desirable uniform distribution of the interface pressure
between the roller and the race. This remedy may increase the bear-
ing stiffness [27], and following to this contrivance, an innovative
method for chamfering the roller edge is being developed using water-
jet processing.
2. Use of water hydrostatic guideway to dissipate the heat generated by
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higher- speed traveling of the table in the grinding machine [28]. In this
case, the guideway is a weld-in-place type to the base, which has a
T- shaped layout and lightweight structure consisting of viscoelastic-
covered steel tubes, i.e., a variant of two-layered plate. More specifi-
cally, four tubes are integrated into one component to form the central
and wing base units. A similar idea was previously employed in the
cross rail (10,000 mm in length) of the vertical turning machine of
Skoda make in 1956, the maximum allowable machining diameter
of which is 12,500 mm. Importantly, the base has a number of welded
and bonded joints.
The higher- speed cutting has furthermore unveiled a serious problem,
i.e., expansion of the tapered hole at the larger end diameter and of the
outer diameter of the spindle nose due to the centrifugal force. To cope
with this new problem especially evident in the case of 7/24 taper, a new
tapered connection, i.e., HSK, was proposed, and the corresponding
research and development has been very active up to now.
Given that the main spindle driving system consists of a built-in-
motor to some extent, another problem is the joint between the rotor of
the motor and the main spindle. In this joint, the question is how to
reduce the magnetic vibration—and to what extent—by realizing the
sure fixation between the rotor and the main spindle. With the advance
of higher- speed cutting, the built-in-motor technology faces new chal-
lenges, i.e., the need to reduce the centrifugal force and dissipate the gen-
erated heat as well as to clarify the effect of the rear bearing of movable
type on the spindle stiffness. In addition, an ever- growing problem is the
tooling system, i.e., the interface between the tool block and the turret
head, which is compatible with higher- speed cutting.
To this end, Fig. 5-27 shows some representative research and devel-
opment subjects related to the machine tool in general as well as specific

5
With the reevaluation of the water lubrication, not only in the machine tool, but also
in the stepper in LSI (large scale integrated circuit) manufacturing, the natural wood mate-
rial, i.e., lignum vitae, is in resurgence, and its modern alternative material is the phenol
resin. For example, in deep hole drilling by the BTA (British Tool Association) method,
the pad made of lignum vitae was employed by Uni Sig Co. in 1982. Lignum vitae was
furthermore used at the bearing of the hydroelectric power generator and propelling
system of the submarine.