HEIDENHAIN TNC 426 (280 476) - Manual (Page 251)

224 8 Programming: Cycles
8.3 Cy
cles f
o
r Dr
illing, T
a
pping and Thr
ead Milling
BORE MILLING (Cycle 208)
1 The TNC positions the tool in the tool axis at rapid traverse FMAX
to the programmed set-up clearance above the workpiece surface
and then moves the tool to the bore hole circumference on a
rounded arc (if enough space is available).
2 The tool mills in a helix from the current position to the first
plunging depth at the programmed feed rate.
3 When the drilling depth is reached, the TNC once again traverses
a full circle to remove the material remaining after the initial
plunge.
4 The TNC then positions the tool at the center of the hole again.
5 Finally the TNC returns to the setup clearance at FMAX. and — if
programmed — to the 2nd set-up clearance with FMAX.
Before programming, note the following:
Program a positioning block for the starting point (hole
center) in the working plane with radius compensation R0.
The algebraic sign for the cycle parameter DEPTH
determines the working direction. If you program DEPTH
= 0, the cycle will not be executed.
If you have entered the bore hole diameter to be the same
as the tool diameter, the TNC will bore directly to the
entered depth without any helical interpolation.