HEIDENHAIN TNC 640 (34059x-04) Cycle programming - Manual (Page 187)

PILOT DRILLING (Cycle 21, DIN/ISO: G121) 7.5
7
TNC 640 | User's Manual Cycle Programming | 3/2014
187
7.5 PILOT DRILLING (Cycle 21, DIN/ISO:
G121)
Cycle run
1 The tool drills from the current position to the first plunging
depth at the programmed feed rate
F.
2 When it reaches the first plunging depth, the tool retracts in
rapid traverse
FMAX to the starting position and advances again
to the first plunging depth minus the advanced stop distance t.
3 The advanced stop distance is automatically calculated by the
control:
At a total hole depth up to 30 mm: t = 0.6 mm
At a total hole depth exceeding 30 mm: t = hole depth / 50
Maximum advanced stop distance: 7 mm
4 The tool then advances with another infeed at the programmed
feed rate F.
5 The TNC repeats this process (1 to 4) until the programmed
total hole depth is reached.
6 After a dwell time at the hole bottom, the tool is returned to the
starting position in rapid traverse
FMAX for chip breaking.
Application
Cycle 21 is for PILOT DRILLING of the cutter infeed points. It
accounts for the allowance for side and the allowance for floor as
well as the radius of the rough-out tool. The cutter infeed points
also serve as starting points for roughing.
Please note while programming:
When calculating the infeed points, the TNC does
not account for the delta value
DR programmed in a
TOOL CALL block.
In narrow areas, the TNC may not be able to carry
out pilot drilling with a tool that is larger than the
rough-out tool.