Power chuck KFD-HS - RÖHM - #13

The clamping force F_Sp of a rotary chuck is the total of 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 Fspo. The clamping force Fsp avialable during the cutting process is, firstly, the initial clamping force Fspo existing with the chuck stationary. This force is then increased or decreased by the centrifugal force F_c on the jaws.

Fsp=Fspo ± Fc [N] (1)

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_sp avialable during the cutting process multiplied by safety factor S_z > 1,5.

The size of this factor is determined by the accuracy of the influence parameters such as loading, clamping coefficient, etc.

Fsp=FspzSz [N] (2)

A safety factor of Sp > 1,5 should be taken into consideration for the static initial clamping force F_spo. Consequently, the following applies for the clamping force with the chuck stationary.

^Fspo ^-Ssp ' ^(Fsp =•= ^Fc)

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 andfalsejaws inwhichthefalsejaws AB canbemo-ved in order to alter the clamping area and the sliding jaws GB approximately maintain their radial position:

Mc =Mcgb + Mcab [mkg] (7)

M_cGB can be obtained from the table below. M_cAB canbecalculatedusingthefollowingformula:

Mcab = mAB * rsAB [mkg] (8)

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.

Formulae (1), (2) and (3) produce the following result for clamping from the outside in:

sp

In this case the centrifugal force Fc is dependent on the mass of all jaws mg, the centre of gravity radius rs and the speed of rotation n. The following formula can be derived:

Fc-(mB'rs)'^-^30ⁿ)²|

The expression mg * rs is called the centrifugal moment Mc

Mc =mg^. rs [mkg] (6)

The following formula applies for determining the permitted speed of rotation for a specific machi­ning job:

Do not exceed the maximum speed of rotation n_max of the chuck (marked on the body of the chuck). This applies even if the calculated permitted speed ofrotation n_permis greater than the maximum speed n_max.

ⁿperm ^:

I Mc

(Nothe the number of jaws for 2 McJ