lemo,
Have no answer, curious, and just some thoughts.

From a numbers point of view, if you divide a 8" circle into 50 equal parts the length between
two parts is 1.0026" and if it was a true circle with just one flat you would have a change in diameter of
.0315" ( 1/32" ).

What are you cutting?

Can you post the Lazycam, cut2d code that you tested with?

What version of Mach and SS plug-in are you using?

RICH

ITS ALL MACH3's FAULT!!! 

Well... cough cough.... NOT... 

Today the problem was found... The Z Axis carriage is pulled around on the gantry using a timing belt and that is linked to the carriage with a little AL block which also tightens the belt. Two 1/4 inch screws are used to lock that block onto the carriage. All was tight... but... the holes were bottomed out... HA! The darn thing was tight enough that there was no indication of a fault while manhandling it. But when the 250lbs gantry stops or accelerates quickly, then it slipped a tiny bit, thus leading to the symptoms of backlash. The holes have been set deeper, the screws tightened tighter. And the friggin flats have taken a vacation. Circles are nice and round now.

Flats -> some sort of backlash or slippage of some kind.

Next time I will rivet, braze, weld, glue, and fuse that bugger to the parts.... Did I forget a method?

Cheers
Lemo

Mach 1 - Lemo 0
Glad you figured it out, now what are you going to do for fun? 
RICH

Nice one, you will not forget that one in a rush.

 

Graham