65
Instruction and maintenance manual
ENGLISH
c) The mobile polar extensions must also be cor-
rectly positioned in order to guarantee an efficient
use of the automatic shimming system. Mobile
extensions must also be alternated.
INCORRECT
POSITION
CORRECT
POSITION
The mobile parts of polar extensions must move
away or forward when sliding along the vertical
plane. This means that their movement should never
be equivalent or parallel (this does not apply to round
mobile extensions).
CORRECT
POSITION
8.4 How to calculate the clamping force
The magnetic clamping force is very easy to calcu-
late, because it is determined by:
• The surface of the magnetic chuck in contact
with the part to clamp
• The conditions of the contact surface of the part
to clamp
• The technical characteristics of the material of the
part to machine
• The type of magnetic chuck used
8.5 Example of how to calculate the
clamping force of a magnetic chuck
Contact surface = 200 cm
2
(
*
)
- Conditions of the part surface = Not machined
(Taverage = 0.6 mm)
- Type of material to machine = C40
- Model of magnetic chuck =
Magnetic chuck
model - For milling operations, with square
poles, series QX or SQ/ST and series QX or
SQ/HD
-
Clamping force per cm
2
= 6 kg/cm
2
(see page 51
in paragraph 3.3.6 - Chart for MILLERS)
Taking into consideration the information provided
above, the clamping force can be calculated by
means of the following formula:
Total clamping force = 6 kg/cm
2
x 200 cm
2
=
12000 kg
This obviously a theoretical calculation that does not
take into account all possible variables that may oc-
cur during actual machining operations (non homog-
enous material with hard points in some sections,
surface with deformations that prevent a perfect
contact between the part and extensions, non lin-
ear surface that prevents the removal of consistent
quantities of materials, etc.). Therefore, it is generally
advisable to consider also a safety factor (Fa) = 0.5:
Thus, the calculation described in the example
above would yield to the following result:
12000 x 0.5 = 6000 kg
(
*
) In order to quickly calculate the contact surface
(cm
2
), count the number of working poles and multi-
ply it by the system value of cm
2
of the pole.
Example: pole with dimensions of 50x50 mm = 25
cm
2
; pole 70x70 = 49 cm
2
)
