Diameter of printed cylinder too small despite calibration

I'm a bit lost, maybe someone has an idea.
I calibrated my VC4 so that when printing a cube the end result is the size I intended it, e.g. CAD says 10mm -> real world is 10mm.

But for whatever reason this does not work on cylinders... I want to print a cylinder diameter 8 mm and height 11 mm. Real world: height 11 mm but diameter 7.5 mm

Is it some setting I have to do?

I tried already with really low speed (40mm/s) but didn't help either.

Later I did a test print of a cylinder 30 mm diameter and 10 mm diameter (primitives from slicer). The resulting diameter was 30.8 mm and 9.8 mm?!?
What am I missing?

KlonkOP•1/19/25, 7:07 AM

I found this behaviour using Orcaslicer and Polymaker Polylite ASA.

KlonkOP•1/19/25, 7:07 AM

I tried now with JAYO PETG. The effect is a bit smaller, but still there. Size should be 8 mm, but is 7.8 mm

crater•1/20/25, 7:02 AM

It might be worth trying to calibrate at a larger scale? E.g. something 100mm long or longer. With a a small cube, small surface deviations - e.g. bulging corners due to pressure advance being slightly off - could throw out your calibration by quite a relatively large percentage when compared to corner bulging on a 100mm cube, say. I don't see any other reason for objects of a similar expected size coming out at different sizes when printed. As a sanity check, you could try printing the cube and cylinders at the same time just to confirm that your cube is indeed still 10mm as expected.

KlonkOP•1/20/25, 10:06 AM

Well I calibrated using califlower. And printing larger parts are absolutely accurate in size.

KlonkOP•1/23/25, 2:58 PM

I still don't know the reason why this happened, but for now I simply upscaled the cylinder diameter in the slicer by 0.2 mm