Siemens Sinumerik 840D sl Programming Manual page 382

Transformations
6.8 Kinematic transformation
A parts program for milling a groove generally comprises the following steps:
1. Selecting a tool
2.
3. Select suitable coordinate offset (frame)
4. Position
5.
6. Select TRC
7. Approach block (position TRC and approach groove side)
8. Groove center line contour
9. Deselect TRC
10.Retraction block (retract TRC and move away from groove side)
11.Position
12.TRAFOOF
13.Re-select original coordinate shift (frame)
Special features
• TRC selection:
TRC is not programmed in relation to the groove side, but relative to the programmed
groove center line. To prevent the tool traveling to the left of the groove side, G42 is
entered (instead of G41). You avoid this if in OFFN, the groove width is entered with a
negative sign.
• OFFN acts differently with TRACYL than it does without TRACYL. As, even without TRACYL,
OFFN is included when TRC is active, OFFN should be reset to zero after TRAFOOF.
• It is possible to change OFFN within a parts program. This could be used to shift the
groove center line from the center (see diagram).
• Guiding grooves:
TRACYL does not create the same groove for guiding grooves as it would be with a tool
with the diameter producing the width of the groove. It is basically not possible to create
the same groove side geometry with a smaller cylindrical tool as it is with a larger one.
TRACYL minimizes the error. To avoid problems of accuracy, the tool radius should only
be slightly smaller than half the groove width.
Note
OFFN and TRC
With TRAFO_TYPE_n = 512, the value is effective under OFFN as an allowance for TRC.
With TRAFO_TYPE_n = 513, half the groove width is programmed in OFFN. The contour
is retracted with OFFN-TRC.
382
Programming Manual, 02/2011, 6FC5398-2BP40-1BA0
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