Siemens sinumerik 840d Programming Manual page 154

Special Motion Commands
5
5.2 Spline interpolation
840D 840D
NCU 571 NCU 572
NCU 573
Distance between nodes:
Node distances are appropriately calculated
internally in the control, but the system is also
capable of processing user-programmed node
distances.
Programming:
PL = Value range as for path dimension
Example of B spline:
All weights 1
N10 G1 X0 Y0 F300 G64
N20 BSPLINE
N30 X10 Y20
N40 X20 Y40
N50 X30 Y30
N60 X40 Y45
N70 X50 Y0
C SPLINE
In contrast to the akima spine, the cubic spline is
continuously curved in the intermediate points. It
tends to have unexpected fluctuations however. It
can be used in cases where the interpolation points
lie along an analytically calculated curve. C splines
use 3rd-degree polynomials.
The spline is not local, i.e. changes to an
interpolation point can influence a large number of
blocks (with gradually decreasing effect).
5-154
FM-NC 810D 840Di
Different weights
N10 G1 X0 Y0 F300 G64
N20 BSPLINE
N30 X10 Y20 PW=2
N40 X20 Y40
N50 X30 Y30 PW=0.5
N60 X40 Y45
N70 X50 Y0
Y
50
40
30
20
10
10
C spline (cubic spline)
P3
P2
P1
P1 to P7: Predefined coordinates
SINUMERIK 840D/840Di/810D/FM-NC Programming Guide Advanced (PGA) − 04.00 Edition
04.00
Check polygon
All weights 1
Different weigths
20 30 40 50 60
Check polygon
N10 G1 X0 Y0 F300 G64
N20 ;omitted
N30 X10 Y20
N40 X20 Y40
N50 X30 Y30
N60 X40 Y45
N70 X50 Y0
P7
P6
P4
P5
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