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7. Calculating the clamping force and speed of rotation
7.1 Determing the clamping force
The clamping force F
all jaw forces acting radially on the workpiece. The
clamping force applied before the cutting process and
with the chuck stationary is the initial clamping force
F
. The clamping force F
spo
process is, firstly, the initial clamping force F
with the chuck stationary. This force is then increased or
decreased by the centrifugal force F
F
= F
F
sp
spo
c
The (--) sign is for clamping forces applied from the
outside in.
The (+) sign is for clamping forces applied from the
inside out.
The clamping force F
process multiplied by safety factor S
7.2 Determining the permitted speed of rotation
7.2.1 Centrifugal force F
Formulae (1), (2) and (3) produce the following result
for clamping from the outside in:
F
spo
F
=
sp
S
sp
In this case the centrifugal force F
the mass of all jaws m
and the speed of rotation n.
The following formula can be derived:
.
.
F
= (m
r
)
(
c
B
s
The expression m
B
moment M
c
.
M
= m
r
c
B
s
7.3 Permitted speed of rotation
The following formula applies for determining the
permitted speed of rotation for a specific machi-
ning job:
30
n
=
π
perm
(Note the number of jaws for Σ M
C
B
R
L
A
A
of a rotary chuck is the total of
sp
avialable during the cutting
sp
spo
on the jaws.
c
[N]
avialable during the cutting
sp
1,5.
²
z
, and centrifugal moment M
c
-- F
[N]
c
is dependent on
c
, the centre of gravity radius r
B
.
n
2
π
) [N]
30
⋅
r
is called the centrifugal
s
[mkg]
.
F
-- (F
S
spo
spz
z)
[min
M
c
(9)
)
c.
Chuck size
r
s
Max. weight in kg
R
max. in mm
a
L
max. in mm
a
Centrifugal moment M
The size of this factor is determined by the accuracy of
the influence parameters such as loading, clamping
coefficient, etc.
F
= F
sp
A safety factor of S
existing
consideration for the static initial clamping force F
Consequently, the following applies for the clamping
force with the chuck stationary.
(1)
F
= S
spo
The (--) sign is for clamping forces applied from the
outside in.
The (+) sign is for clamping forces applied from the
inside out.
The following formula applies to chucks with sliding
c
and false jaws in which the false jaws AB can be mo-
ved in order to alter the clamping area and the sliding
jaws GB approximately maintain their radial position:
M
= M
c
(4)
M
cGB can be obtained from the table below.
M
cAB can be calculated using the following formula:
s
M
= m
cAB
(5)
The clamping forces can be obtained by referring to
the clamping force/speed of rotation diagram (see
page 28) when using standard series production
jaws allocated to specific chuck by the chuck
manufacturer.
(6)
Do not exceed the maximum speed of rotation
n
of the chuck (marked on the body of the
max
--1
chuck). This applies even if the calculated
]
permitted speed of rotation n
the maximum speed n
130
170
A
54
66,7
B
23
36,5
C
29
0,22
0,7
39
18
0,015
0,030
GB [mkg]
C
.
S
[N]
spz
z
1,5 should be taken into
²
p
.
(F
F
)
[N]
sp
sp
c
+ M
[mkg]
cGB
cAB
⋅
r
[mkg]
AB
sAB
Important:
is greater than
perm
.
max
210
254
75
95
36,5
45
53
53
54,5
0,88
1,4
52
68
80
29
29
30
0,051
0,125
(2)
.
spo
(3)
(7)
(8)
315
400
95
45
54,5
1,4
110
30
0,300
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