Kitagawa BBT200, Instruction Manual

Page: 22 / 50

21
Analysis of the gripping force, input force and rotation speed using Fig. 8 is carried out
as shown below.
・
For example, in the case of BBT206 standard soft jaw (mass moment 59.1kg
・
mm),
it cannot exceed 6000min
-1
(rpm), and the gripping force loss due to the centrifugal
force at this rotation speed is 26kN (approx. 2651kgf). The required static gripping
force for the dynamic gripping force (gripping force loss by static gripping force -
centrifugal force) to become 1/3 of the static gripping force is 38.9kN, and the
required input to obtain this gripping force is 13.3kN. However, it is necessary to use
at the gripping part center height H=17.2 mm or less.
・
If the gripping part center height H is high, it is necessary to lower the static gripping
force.
・
If the top jaw mass moment is large, the rotation speed needs to be lowered.
・
If the rotation speed is high, the gripping force loss due to the centrifugal force
becomes large. The centrifugal force is proportional to the square of the rotation
speed.
The required static gripping force and input force required at the rotation speed in use are
predicted from Fig.8, however, it contains a number of hypothetical conditions. Therefore, it
is necessary to only use these as reference, and the processing conditions must be
determined after trial cutting without fail.
・
In the case of inside diameter gripping, keep the input to 1/2 of the allowable
maximum input or less. In the case of inside diameter gripping, the length of
engagement of the master jaw and the dovetail groove is shorter when
compared to the outside diameter gripping, therefore, the chuck will break, the
work will fly out and this is dangerous.
・
In the case of using only 1 jaw for gripping reduce the input force by 1/2 or
more. If it is used without lowering the input, the input which is normally
applied evenly onto 2 of the jaws is concentrated onto 1 of the jaws. Otherwise
the chuck will break, the work will fly out and this is dangerous.