Holding Forces; A) Holding Force And Shearing Force; B) Pole Pitch And Thickness Of Work Piece; C) Influence Of Air Gaps - Sav 243.40 Operating Instructions Manual

WORKHOLDING AND AUTOMATION
3. Operation
a) Loading:
- remove all burrs and unevenness at the contact surface of the work piece.
- clean the pole plate and the surface of work piece.
- position the work piece and switch the magnet on by pushing the green push button.
- check sufficient holding force.
- position a shielding and start machining
b) Unloading:
- support work piece, if it is not horizontal.
- switch the chuck off by pushing the red push button. The blinking of LED will show you the
demagnetization cycle. Wait, until demag cycle is finished (red lamp will remain on).
- remove work piece.

4. Holding forces

a) holding force and shearing force:

The listed holding forces are always for
directions perpendicular to the pole plate. The
shearing force is dependant on the roughness
of work piece 15 to 30% of holding force. It is
dependant on the roughness and adhesion
of the work piece.
The nominal holding forces are calculated
on a test piece made out of mild steel St37,
ground and with dimensions 100x100x40
mm. The following conditions need to be
considered as well.

b) pole pitch and thickness of work piece:

For creation of holding force the only the
part of magnetic field used is that which is
contained within the work piece. If the pole
pitch is too large compared with thickness of
work piece, loss of holding force will occur.
The minimum thickness of work piece has
to be considered.

c) influence of air gaps:

Air gaps between work pieces and pole
plate increase the magnetic resistance and
cause a drop of holding force. Generally,
magnetic chucks for milling have got a better
performance at air gaps than chucks for
grinding. The named values in the sketch
are only for reference.
16
BAL 243.40 / .41 / .42 / .99
OPERATING INSTRUCTIONS
For Electro Magnetic Chucks Rectangular
S N
thickness of work piece larger than field heigth
S N
thickness of work piece lower than field heigth
holding forces
20% - 50% 50% - 70%
work piece
V 2.0
holding force
shearing force
chuck
work piece chuck
S N S N
work piece chuck
S N S N
70% - 80% 80% - 90%
chuck