Fixed rad... am I doing it correctly

Hi folks
I have a crappy feature to try and measure (Image enclosed). It's a R75.0mm milled arc, only about 4% (14º) of the circumference to measure on a fairly large rad.
I'm working from CAD and I'm starting with a fixed rad circle with 30 points (I have no scanning head), then aligning on that FR circle, doing a 2nd fixed rad circle, again 30 points and aligning now on that 2nd FR circle, then taking a 3rd circle, but least square this time, again 30 points. I'm getting fairly large errors from print, which may well be absolutely true, just checking if I'm approaching it correctly and my results are as trustworthy as possible?
Thanks folks

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dwade 11 months ago

I've had very good success with short arc length diameters using an open linear scan and constructing a BFRE circle from the scan hits and make sure that you are in the correct workplane when constructing the circle.

SC_OD =FEAT/SCAN,LINEAROPEN,NUMBER OF HITS=150,SHOW HITS=NO,SHOWALLPARAMS=NO
MEAS/SCAN
BASICSCAN/LINE,NUMBER OF HITS=150,SHOW HITS=NO,SHOWALLPARAMS=NO
ENDSCAN
ENDMEAS/
OUTER_DIA =FEAT/CIRCLE,CARTESIAN,OUT,LEAST_SQR,NO
THEO/<1.163,-10.72,2.718>,<0,1,0>,17.951
ACTL/<1.163,-10.72,2.718>,<0,1,0>,17.951
CONSTR/CIRCLE,BFRE,2D,SC_OD.HIT[1..SC_OD.NUMHITS],,
OUTLIER_REMOVAL/OFF,3
FILTER/OFF,UPR=0

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dwade 11 months ago

SC_OD =FEAT/SCAN,LINEAROPEN,NUMBER OF HITS=150,SHOW HITS=NO,SHOWALLPARAMS=NO
MEAS/SCAN
BASICSCAN/LINE,NUMBER OF HITS=150,SHOW HITS=NO,SHOWALLPARAMS=NO
ENDSCAN
ENDMEAS/
OUTER_DIA =FEAT/CIRCLE,CARTESIAN,OUT,LEAST_SQR,NO
THEO/<1.163,-10.72,2.718>,<0,1,0>,17.951
ACTL/<1.163,-10.72,2.718>,<0,1,0>,17.951
CONSTR/CIRCLE,BFRE,2D,SC_OD.HIT[1..SC_OD.NUMHITS],,
OUTLIER_REMOVAL/OFF,3
FILTER/OFF,UPR=0

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