Thread Undercuts (Cycle940) - Siemens SINUMERIK 840D sl Operating Manual

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Table of Contents

Programming technology functions (cycles)

* Unit of feedrate as programmed before the cycle call

Thread undercuts (CYCLE940)

The "Thread undercut DIN" or "Thread undercut" cycle is used to program thread undercuts

to DIN 76 for workpieces with a metric ISO thread, or freely definable thread undercuts.

Approach/retraction

1. The tool first moves to the starting point calculated internally in the cycle at rapid traverse.

2. The first cut is made at the machining feedrate, starting from the flank and traveling along

3. The tool moves to the next starting position at rapid traverse.

4. Steps 2 and 3 are repeated until the thread undercut is finished.

5. The tool moves back to the starting point at rapid traverse.

During finishing, the tool travels as far as cross-feed VX.

Form F machining position:

Undercut size according to DIN table:

e.g.: F0.6 x 0.3 (undercut form F)

Reference point X ∅

Reference point Z

Allowance in X ∅ (abs) or allowance in X (inc)

Allowance in Z (abs) or allowance in Z (inc) – (for undercut form F only)

Cross feed ∅ (abs) or cross feed (inc)

the shape of the thread undercut as far as the safety distance.

Operating Manual, 03/2013, 6FC5398-8CP40-3BA1

Sinumerik 828d turning