Siemens SINUMERIK 840D sl Programming Manual page 290

Special motion commands
4.6 Settable path reference (SPATH, UPATH)
Programming
N10 G1 X0 A0 F1000 SPATH
N20 POLY PO[X]=(10,10) A10
or:
Programming
N10 G1 X0 F1000 UPATH
N20 POLY PO[X]=(10,10) A10
In block N20, path S of the FGROUP axes is dependent on the square of curve parameter U.
Therefore, different position arise for synchronized axis A along path X, according to whether
SPATH or UPATH is active.
Restrictions
The path reference set is of no importance with
● linear and circular interpolation,
● in thread blocks and
● if all path axes are contained in FGROUP.
Description
During polynomial interpolation - and thus the polynomial interpolation is always understood
● in the narrow sense (POLY),
● all spline interpolation types (ASPLINE, BSPLINE, CSPLINE) and
● linear interpolation with compressor (COMPON, COMPCURV)
- are the positions of all path axes i specified by the polynomials pi(U). Curve parameter U
moves from 0 to 1 within an NC block, therefore it is standardized.
The axes to which the programmed path feed is to relate can be selected from the path axes
by means of language command FGROUP. However, during polynomial interpolation, an
interpolation with constant velocity on path S of these axes usually means a non constant
change of curve parameter U.
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Programming Manual, 06/2009, 6FC5398-2BP20-0BA0
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