HEIDENHAIN CNC Pilot 4290 V7.1 - Manual (Page 241)

HEIDENHAIN CNC PILOT 4290 241
4.22 Thr
e
ad Cy
cles
You can calculate the minimum run-in and run-out length with the
following equation.
Starting angle C: At the end of the “run-in path B” the spindle is at
the “starting angle C” position. Therefore, if the thread is to start
exactly at the starting angle, position the tool by the run-in length or a
multiple of it in front of the beginning of the thread.
Look-ahead: G31 does not switch the look-ahead off. You can switch
the look-ahead off and on again in separate NC blocks (see “Velocity
feedforward G918” on page 307).
The individual thread cuts are calculated from the thread depth,
maximum approach I and type of approach V.
You influence the thread cutting with the smooth threading (see
“Thread switch G933” on page 239).
Smooth threading switched off
Run-in length: B = 0.75 * (F*S)² / a + 0.15
Run-out length: P = 0.75 * (F*S)² / e + 0.15
Smooth threading switched on
Run-in length: B = 0.75 * (F*S)² / a * 0.66 + 0.15
Run-out length: P = 0.75 * (F*S)² / e * 0.66 + 0.15
„ F: Thread pitch in mm/revolution
„ S: Speed in revolutions/second
„ a, e: Acceleration in mm/s² (see “Acceleration at block start/block
end” in MP 1105, ...)
„ Feed rate stop becomes effective only at the end of a
thread cut.
„ Feed rate override is not effective.
„ Do not use the spindle override if the feedforward is
switched off!
Danger of collision!
„ An excessive run-out length P might cause a collision.
You can check the run-out length during the simulation.
„ The spindle reference is derived from the feed per
revolution that was programmed last.