Die & Mould Making - CNC - Computer Numerical Control

36
ENTRANCE AND EXIT OF CUT
Every time a cutter
goes into cut, the inserts
are subjected to
a large or small shock
load depending on
material, chip cross
section and the type of
cut. The initial contact
between the cutting
edge and workpiece may be very unfavourable
depending on where the edge of the
insert has to take the first shock. Because
of the wide variety of possible types of
cut, only the effects of the cutter position
on the cut will be considered here.
Where the centre of the cutter is positioned
outside the workpiece (A) an unfavourable
contact between the edge of the insert and
the workpiece results.
Where the centre of the cutter is positioned
inside the workpiece (B) the most favourable
type of cut results.
B
+ -
A
The most dangerous situation however, is
when the insert goes out of cut leaving the
contact with the workpiece. The cemented
carbide inserts are made to withstand compressive
stresses which occur every time an
insert goes into cut (down milling). On the
other hand, when an insert leaves the workpiece
when hard in cut (up milling) it will
be affected by tensile stresses which are
destructive for the insert which has low
strength against this type of stress. The
result will often end in rapid insert failure.
-
+
-