HEIDENHAIN TNC 426, User Manual

Page: 141 / 502

HEIDENHAIN TNC 426, TNC 430 115
5.4 Thr
ee-Dimensional T
ool Compensation
Definition of a normalized vector
A normalized vector is a mathematical quantity with a value of 1 and a
direction. The TNC requires up to two normalized vectors for LN
blocks, one to determine the direction of the surface-normal vector,
and another (optional) to determine the tool orientation direction. The
direction of a surface-normal vector is determined by the components
NX, NY and NZ. With an end mill and a radius mill, this direction is
perpendicular from the workpiece surface to be machined to the tool
datum PT, and with a toroid cutter through PT‘ or PT (see figure at
upper right). The direction of the tool orientation is determined by the
components TX, TY and TZ.
Permissible tool forms
You can describe the permissible tool shapes in the tool table via tool
radius
R and R2 (see figure at upper right):
n
Tool radius R: Distance from the tool center to the tool
circumference.
n
Tool radius 2:
R2:
Radius of the curvature between tool tip and tool
circumference.
The ratio of
R
to
R2
determines the shape of the tool:
n
R2
= 0: End mill
n
R2 = R: ball-nose cutter.
n
0 <
R2
<
R:
Toroid cutter
These data also specify the coordinates of the tool datum PT.
The coordinates for the X, Y, Z positions and the surface-
normal components NX, NY, NZ, as well as TX, TY, TZ
must be in the same sequence in the NC block.
Always indicate all of the coordinates and all of the
surface-normal vectors in an LN block, even if the values
have not changed from the previous block.
3-D compensation with surface-normal vectors is only
effective for coordinates in the main axes X, Y, Z.
If you insert a tool with oversize (positive delta value), the
TNC outputs an error message. You can suppress the
error message with the M function
M107 (see
“Prerequisites for NC blocks with surface-normal vectors
and 3-D compensation,” page 109).
The TNC will not display an error message if an entered
tool oversize would cause damage to the contour.
Machine parameter 7680 defines whether the CAD
system has calculated the tool length compensation from
the center of sphere P
T
or the south pole of the sphere
P
SP
(see figure at right).
P
T
R R R
R2
P
T
P
T
R2
P
T
'
P
T
P
SP