Thread Milling (Cycle70) - Siemens sinumerik 840D sl Operating Manual

Programming technology functions (cycles)
8.4 Milling
8.4.11

Thread milling (CYCLE70)

Function
Using a thread cutter, internal or external threads can be machined with the same pitch.
Threads can be machined as right-hand or left-hand threads and from top to bottom or vice
versa.
For metric threads (thread pitch P in mm/rev), the cycle assigns a value (calculated on the
basis of the thread pitch) to the thread depth H1 parameter. You can change this value. The
default selection must be activated via a machine data code.
The entered feedrate refers to the machining. However the feedrate of the cutter center point
is displayed. That is why a smaller value is displayed for internal threads and a larger value
is displayed for external threads than was entered.
Approach/retraction when milling internal threads
1. Positioning on retraction plane with rapid traverse.
2. Approach of starting point of the approach circle in the current plane with rapid traverse.
3. Infeed to a starting point in the tool axis calculated internally in the controller with rapid
4. Approach motion to thread diameter on an approach circle calculated internally in the
5. Thread cutting along a spiral path in clockwise or counterclockwise direction (depending
6. Exit motion along a circular path in the same rotational direction at programmed feedrate.
7. With a programmed number of threads per cutting edge NT > 2, the tool is fed in (offset)
by the amount NT-1 in the Z direction. Points 4 to 7 are repeated until the programmed
thread depth is reached.
8. If the plane infeed is less than the thread depth, points 3 to 7 are repeated until the thread
depth + programmed allowance is reached.
9. Retract on the thread center point and then to retraction plane in the tool axis in rapid
traverse.
Please note that when milling an internal thread the tool must not exceed the following value:
Milling cutter diameter < (nominal diameter - 2 · thread depth H1)
370
Machine manufacturer
Please also refer to the machine manufacturer's instructions.
traverse.
controller with the programmed feedrate, taking into account the finishing allowance and
maximum plane infeed.
on whether it is left-hand/right-hand thread, for number of cutting teeth of a milling plate
(NT) ≥ 2 only 1 rotation, offset in the Z direction).
Operating Manual, 07/2010, 6FC5398-8CP40-0BA0
Turning