HEIDENHAIN TNC 640 (34059x-05) Cycle programming - Manual (Page 283)

TOLERANCE (Cycle 32, DIN/ISO: G62) 11.5
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TNC 640 | User's Manual Cycle Programming | 1/2015
283
11.5 TOLERANCE (Cycle 32, DIN/ISO: G62)
Cycle function
Machine and TNC must be specially prepared by the
machine tool builder for use of this cycle.
With the entries in Cycle 32 you can influence the result of
HSC machining with respect to accuracy, surface definition and
speed, inasmuch as the TNC has been adapted to the machine’s
characteristics.
The TNC automatically smoothens the contour between two path
elements (whether compensated or not). The tool has constant
contact with the workpiece surface and therefore reduces wear on
the machine tool. The tolerance defined in the cycle also affects the
traverse paths on circular arcs.
If necessary, the TNC automatically reduces the programmed feed
rate so that the program can be machined at the fastest possible
speed without short pauses for computing time.
Even if the TNC
does not move with reduced speed, it will always comply with
the tolerance that you have defined.
The larger you define the
tolerance, the faster the TNC can move the axes.
Smoothing the contour results in a certain amount of deviation
from the contour. The size of this contour error (
tolerance value)
is set in a machine parameter by the machine manufacturer. With
CYCLE 32 you can change the pre-set tolerance value and select
different filter settings, provided that your machine tool builder has
implemented these features.
Influences of the geometry definition in the CAM
system
The most important factor of influence in offline NC program
creation is the chord error S defined in the CAM system.
The maximum point spacing of NC programs generated in a
postprocessor (PP) is defined through the chord error. If the chord
error is less than or equal to the tolerance value
T defined in Cycle
32, then the TNC can smooth the contour points unless any special
machine settings limit the programmed feed rate.
You will achieve optimal smoothing if in Cycle 32 you choose a
tolerance value between 110-% and 200-% of the CAM chord error.