Arcs are extremely choppy

I know that the buildbotics controller does not support arcs but this is troubling. I’ve seen others create smooth topographic cuts on this machine and wonder why mine is so bad.

This is a 2d contour out of fusion 360 with a downcut .25 end mill.

I’ve set built in tolerance to .005mm and the max-deviation on the machine matches the .005mm

Is there anything else I should be looking at? Oh and circular interpolation is checked on.

Thank you in advance.


Hi @MustCreateThings

What were the tolerances you set in fusion? And were you using smoothing? I understand the lack of Arc support in the stock controller. I upgraded to the centroid acorn to fix that :wink:

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Hello @alldaysammyj and thank you for the reply.

I did not have smoothing on and washing it would be the fix.

This is and adaptive clearing path with smoothing on and a 0.020” step down.

It’s odd all of the paths seem smooth until it gets to the last ‘finishing’ path before stepping down.


Any other thoughts would be greatly appreciated. Thanks again!!!


View your G-code file and see if you are actually getting G2or G3 (arc moves) for each the arcs. They look like linear interpolation of arcs.

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@SkyKam thank you for the reply!

Here are a couple photos from the controller after the files have been uploaded. It looks to have both G2 and G3 codes present.

The first image is for the outer profile and the second is the inner stepped surfaces.

The inner steps have a series of small arcs instead of a half circle. Perhaps when Fusion computes the XY values for a Z height these are not perfect half circle arcs so it breaks the path up into small arcs. Probably not a big deal if you are just roughing out the inside for a later finishing tool. I wonder if a 3D pocket tool path would do anything different? I typically associate the 2D contour tool path with vertical walls when using an end mill and use a 3D tool path when the walls are sloped.

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@SkyKam thank you for the suggestions! I ended up building the steps manually and running a 2d pocket toolpath and it turned out much better. I think it had to do with it being a roughing not finishing path.

And I made sure I posted the path in mm measurements too. Not sure if that did anything.

Thanks again!