Odd Artifacts on bottom few layers of vase print ABS part

Hello All,

I've been working on optimizing an ABS profile in Cura 4.8.0 for printing a small test part (a miniature studded vase in this case), but I am running into issues with the outside surface quality of the first few layers.

The part is printed in vase mode (spiralize outer contour) with the following basic settings:

Printer: Airwolf3D AXIOM Dual Direct Drive
Nozzle Size: 0.5 mm
Layer Height: 0.25 mm
Line Width: 0.5 mm
Top/Bottom Thickness: 1.2 mm
Print Temperature: 250 C
Bed Temperature: 130 C
Print Speed: 80 mm/s
Outer wall Speed: 60 mm/s
Top/Bottom Speed: 40 mm/s

It seems that the wall layers that correspond with the Bottom thickness have the worst quality (see attached picture). Everything above it seems to print really nicely.

What I have tried so far:

1. Adding a brim (thinking the heated bed might be overheating it) - no change
2. Reducing the print temperature thinking it was just overheating - no noticeable difference
2. Slowing down the outer wall speed (first from 60 mm/s to 40, and then all the way down to 15 mm/s) - no noticeable change in quality.

It seems that the presence of the bottom layers is doing "something" but I'm stumped. Any ideas?

Thanks!
Jason O

Edited 1 time(s). Last edit at 02/26/2021 11:03PM by Jdo300.

Why are top and bottom thickness not multiples of the layer thickness?

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

!!!!!!!! Please confirm the bed temperature?

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the_digital_dentist
Why are top and bottom thickness not multiples of the layer thickness?

That was a setting leftover from a previous profile version that I based this one on.

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MCcarman
!!!!!!!! Please confirm the bed temperature?

Yikes! Yes, that was a typo. The Bed temperature should be 130, not 230, haha! I corrected it in the original post also.

- Jason O

Bed temp seems high. I would try it at 100.
There is some evidence of shrinkage on the solid layers and the high temperature will affect this.

Bed temp of 130 seems high. Typical recommendation is 110 degC. However, I find that 115 degC makes a noticeably better stick of part to Kapton bed for the ABS I'm currently using.

Recently, I've been experimenting with printing the part at 1-2mm above the bed to allow that first desired layer to shrink along with the other higher layers. In Cura, you have to change general settings to allow this. I've had some success with it but still trying with more parts before concluding that it is good. It is basically trying to get the benefits of a raft without the material and time needed for a raft. Will also try with different support patterns too to see if there is an effect that way. Like, a cross-hatch would likely have more isotropic properties than the default zigzag. But, where I want XY shrinkage movement in the supports, cross-hatch is possibly not the greatest. We'll see.