Nylon dimensional accuracy in the Z direction

Hi all,

In the last few days I have been struggling to print a part for an RC project in nylon on my P1s. I am using Polymide CoPa by Polymaker. Initially one if the issues was roughness on overhangs but I think I managed to mostly solve this:

The left-most shaft is the latest print and it is mostly acceptable, but you can see what the previous versions looked like before I slowed down the overhang speeds to 20 mm/s.

However, my main issue is the dimensional accuracy. In particular, the shaft loses shape in the z-axis direction. I printed a copy in PAHT-CF and by comparison it came out perfect:

PAHT-CF is on the left and Polymide CoPa is on the right. Both are printed with the same settings (0.15 layer height, 100% infill, 3 walls, with their respective print profiles). Both filaments are dried.

Notice how the hex shape is skewed and the whole shaft is taller on the z-axis on the CoPa print.

Does anyone have an idea about how to address this?

Obviously if it was bigger in alm directions I would scale it, but it seems it is more complicated than that…

Thanks in advance!

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