HEIDENHAIN TNC 426, User Manual

Page: 272 / 502

246 8 Programming: Cycles
8.3 Cy
cles f
o
r Dr
illing, T
a
pping and Thr
ead Milling
HELICAL THREAD DRILLING/MILLING
(Cycle 265)
1 The TNC positions the tool in the tool axis at rapid traverse FMAX
to the programmed setup clearance above the workpiece surface.
Countersinking at front
2 If countersinking is before thread milling, the tool moves at the
feed rate for countersinking to the sinking depth at front. If
countersinking is after thread milling, the tool moves at the feed
rate for pre-positioning to the countersinking depth.
3 The TNC positions the tool without compensation from the center
on a semicircle to the offset at front, and then follows a circular
path at the feed rate for countersinking.
4 The tool then moves in a semicircle to the hole center.
Thread milling
5 The tool moves at the programmed feed rate for pre-positioning to
the starting plane for the thread.
6 The tool then approaches the thread diameter tangentially in a
helical movement.
7 The tool moves on a continuous helical downward path until it
reaches the thread depth.
8 After this, the tool departs the contour tangentially and returns to
the starting point in the working plane.
9 At the end of the cycle, the TNC retracts the tool in rapid traverse
to set-up clearance, or — if programmed — to the 2nd set-up
clearance.
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 of the cycle parameters depth of thread
or sinking depth at front determines the working direction.
The working direction is defined in the following
sequence:
1st: Depth of thread
2nd: Depth at front
If you program a depth parameter to be 0, the TNC does
not execute that step.
The type of milling (up-cut/climb) is determined by the
thread (right-hand/left-hand) and the direction of tool
rotation, since it is only possible to work in the direction of
the tool.