Hi All,

Im just playing with my buddies Surfcam 2000, Im fumbling with it really.  Anyway I selected the inside of a 42mm dia circle.  Profiling.  Tool diam in SC is 8mm and TIP selected.  When I place a pencil in the machine it scribes a 68mm dia circle.  Why is this so big. Id expect the pencil to draw a 34mm circle.  ie 42-8mm tool dia =34.

See the G code surfcam created.  Perhaps Mach3 doesn't like the post type?

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G17 G40 G80 G90
T21 M6
S1194 M3
G0 G90 G54 X-17. Y0
G43 Z25. H21 M8
G0 Z2.
G1 Z0 F71.6
G3 I17. J0 F143.2
G0 Z25.
G0 M9
G28
M30
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Hi Paul,

Looking at your Gcode, the circle comes out at 34mm diameter here.
Perhaps you have your motor steps per unit set incorrectly ??


Tweakie.

I sure the the steps are set ok.  Becuase when I measure straight movements in X and Y they are perfect.  Ie if I ask X to say move 50mm it moves 50mm same for Y, this is confirmed.  Also the circle is perfectly round just not the right diameter (68mm).  I could only think it was the post processor churning out the wrong code someplace.

Problem solved by Jeff Birt, he advised I needed to change the "IJ" settings in mach3 general config to incremental not absolute as it was set as.  

All good now