Object dimension accuracy in printing

Have anyone had any luck in getting the K8400 to printer circles with correct? Mine are always printed to small. eg. 11.5 mm compared to expected 12.0 mm

Norberg, you can read about this problem here: viewtopic.php?f=62&t=15046&hilit=Polygon

I would also like an answer to this question. I find that the diameter of holes is smaller than it should be, resulting in problems when fitting parts.

monza64: The proposal from that thread to oversize the holes is not good enough. It might work when you design the part yourself. But what i have found and i think several others with the K8400 is that K8400 creates much smaller holes compared to other printers, with the result of printing files from thingiverse with dimension of the holes that works on other printers sadly fails on the K8400.

A few examples of prints that i have tried but fails due to dimension issues:
thingiverse.com/thing:342198 - This bit is specifically designed to test that you can print parts that fits, however fails on K8400, the parts cant be put together.
thingiverse.com/thing:34778 - The bolts does not fit in the holes.
thingiverse.com/thing:185912 - The plugs does not fit in the holes.

The main problem seems to be this one : [quote]Extrusion width and Flow rate are not precisely calibrated, causing actual extruded thread width to be wider than what the settings expected. [/quote]. The default values for the 8400 are way too high : too hot, too much flow. I’ve reduced the temps to 195° for PLA with a flow rate about 70-72%. And don’t forget to reduce the flow for the first layer or you’ll get “bell-bottoms” on your prints.

raby:
Lowering the flow rate helps a bit. I currently run with e-step(configured in cura) of 148 and 100% flow rate, which would be the same as 74% with the original estep. For temperature i currently run with 195°, i have tried lowering it to 190° without noticeable difference.

Are you able to print eg. Part Fitting Calibration(S-Plug) or Euro XY calibration correctly with your printer and settings?

The “Euro XY calibration” i have gotten to fit a euro coin with quite a bit of force when configuring the nozzel size to 0.40 and flow rate to 90% (would be 66% with standard estep). But then the quality of the surface starts to degrade considerably. To get the S-Plug to fit i had increase the nozzel size further to 0.45, then i could get the pieces to fit with a lot of force. The surface quality however is terrible.

By adjusting the nozzel size i try to force cura to make the inner circles bigger since it would expect the filament pushed out of the nozzel to be 0.45 instead of 0.35.