Rohm Norm RN 1391 Informaciones Y Directivas Generales Para El Empleo De Instalaciones De Sujeción Accionadas Por Fuer página 47

Re. b) (see Determining the Required Clamping Force of a Power Chuck
[} 40])
At high speeds, the clamping force of the rotating lathe chuck is greatly influ-
enced by the centrifugal forces of the jaws. These forces must be taken into
account when determining the initial clamping force F
mula is:
F = S ∙ (F
spo SP
The (+) sign applies to external clamping.
The (-) sign applies to internal clamping.
where:
F = experimentally determined total centrifugal force of the clamping jaws
c
from the "clamping force-speed" diagram
The clamping force curves refer to the hard, stepped jaws of the chuck.
S = safety factor for the initial clamping force in accordance with VDI Re-
sp
commendation 3106 ≥ 1.5
If extremely heavy top jaws (special jaws) are used, the centrifugal forces F
can be calculated with the following formula:
where:
m = jaw mass in kg
r = the radius of the centre of gravity of the jaws in cm
n = speed rpm
F = centrifugal force at speed daN
c
η = efficiency
η can be roughly estimated as 0.4 ≤ η ≤ 0.6
If the mass of all jaws (basic jaws with top jaws) is entered at "m", the
sum of the centrifugal forces is calculated.
Re. c) (see Determining the Required Clamping Force of a Power Chuck
[} 40])
The actuating force bears a given relationship to the total clamping force, de-
pending on the type of chuck employed. The values for the actuating force
can be obtained from the clamping force/actuating force diagram.
In special cases where the centrifugal forces of the jaws are too high in com-
parison with the initial clamping force and power chucks with standard top
jaws cannot be used, certain operations can be carried out with aluminium top
jaws of special strength.
RN-1391
Reference Speed and Clamping Force Calculation |
± F )
SPZ C
900,000
. The applicable for-
spo
47 / 138
2
EN
c