Cylinder comes out too small

Bambu Lab H2D
1

Hi

I have designed a 50 mm long cylinder in Fusion 360 with an inner diameter of 44.5 mm and an outer diameter of 54.2 mm. Length 50mm.

I printed it with nylon (AddNorth Adura) filament, 100% infill, using the generic PA profile, and the result is 43.9 x 53.6 mm. Hence 0.6 mm too small on both outer and inner diameter.

I have previously printed it with PLA on an Ultimaker S5, and then it came out good. Within 0.1mm on both outer and inner diameter.

Any ideas on why it comes out too small and how to adjust for this?
Adjusting the “error” in fusion is a possibility, but in all honesty a poor workaround. I want to get out from the printer what I design :wink:

I guess the next step has to be to print a calibration cube or something. But then again, my cylinder is just as much a “calibration cube”, as a calibration cube is :slight_smile:

Thanks!

2

Welcome to nylon. Unless you’re using fiber filled, expect 2-3% shrinkage. You can try adding the shrinkage factor in the filament options, or print slower. I assume you have chamber heating on. There’s also PA12 which is about 1.5% shrinkage which can be a bit more manageable than PA6.

3 Likes
3

partferret is spot on about nylon :grinning:

4

For dimensionally accurate prints, with some materials, I believe you may need to calculate “shrinkage” then apply a correction factor in the form of resizing in the slicer.

Further reading:

5

Thanks! I suspected something like that, but at the same time I would have expected such known characteristics to already be part of the profile.

I’ll have a look at how to adjust for this shrinkage then.

6

It’s not just Nylon. All filaments need adjustments to be close. I consistently see 0.5 mm outages (too small) even with PLA (for hole bores). The auto X/Y adjustment option helps to get it in line with the normal variance but could still need tuning.