Faceting/waves in internal bore

I am trying to machine an elliptical bore in annealed PH 17-4 round stock (see photo below) with a Haas TM-1P. The part is held in custom aluminum soft jaws. The bore is around 1.5" diameter and I am using a 3/8" 4 flute AlTiN Kyocera end mill. I've roughed most of the stock with a radius endmill, leaving around 8 mils of radial and axial stock, then I come in for the finish pass with the square end mill.

The central rod shown is cut in the same pass with the same tool and comes out with a very nice surface finish. However, as you can see in the picture, the outer bore is faceted/wavy. I have tried a bunch of different things to improve the surface finish - faster and slower feeds, multiple depths, spring passes, climb and conventional milling, and even different toolpath smoothing options. None of these changes did anything - the patterns is very consistent.

Any ideas?

Thanks!
Ben

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Have you tried a profile ramping operation? What kind of SFM and feed per tooth?

Is this from a cam system?


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Are you cutting with a arc move or is it line segments


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I am using a 2D contour toolpath. It looks like it is a bunch of straight line segments despite smoothing being in. I am trying to get it to output arcs but there seems to be some interactions I don't understand between tolerances, smoothing, and the options in the post code, but I bet this is the problem. Thanks!

(2D Contour6)
N34445 G1 X-0.0406 Y0.4331 F400.
N34450 G0 Z0.6
N34455 Z-0.2195
N34460 G1 Z-0.9975 F5.322
N34465 G3 Y0.4706 Z-1.035 J0.0375 K0.
N34470 G1 Y0.4806 F15.
N34475 G17 G2 X-0.0031 Y0.5181 I0.0375 J0.
N34480 G1 X0.0186
N34485 X0.0558 Y0.5159
N34490 X0.0926 Y0.5115
N34495 X0.1291 Y0.5048
N34500 X0.165 Y0.4961
N34505 X0.2001 Y0.4852
N34510 X0.2343 Y0.4722

That fixed it - smoothing had to be set to 3 times the tolerance in HSM or it wouldn't smooth and just used line segments.

I fight with that a lot - that is why I asked about the helical boring cycle since for some reason HSM seems to like to output those in arcs without worrying about futzing with smoothing.