Question about problem / backlash

[tikka308]

I milled this part last night using the built-in "Shapes" wizard by German Bravo in Mach 3 (registered version). I used the circle function with a 0.75" radius and the G-code tool-path window showed what appeared to be a perfect circle.

I milled the part and noticed that something is wrong. The x-axis seems OK - it was 1.493" in diameter. However, the Y-axis of the circle was WAY off at 1.315". Any thoughts on what the problem could be or how I can further diagnose?

FYI I was cutting Delrin, 1/4" 2-flute endmill, 0.1" cuts at 1,000 RPM. Mill sound ed fine through the cut and cut the shape wrong, but consistently wrong on each pass.

Thanks!

[project5k]

check your motor settings, looks to me like if your x and y motors, gearing and screws are identicle you have different settings in the steps/inch setting...

if the x and y arent the same, ie different pitch screws, or different gearing or something like that then you need to redo the math for your steps per inch settings...

one other thought, what kinda drivers are you using.. maby one is set for a different level of microstepping than the other?
like 1/2 on one and 1/4 on the other or something like that...