Distortion/Shrinkage at Bottom of Print

[minuteman64 4]

Trying to print a hollow cylinder in ABS.  OD is 23mm and wall thickness is 1.5mm.  Height 30mm.  Having trouble getting bottom without the "(" shrinkage (see photo).   Tried raft and brim - no difference.  Both raft and brim seemed fused to cylinder (hard to remove).  Currently printing at 240 extruder and 105 bed.  Printing bottom 10mm at 1/2 normal print speed.

 

Using Anet A8 in enclosure.  Cura 3.2.1 is slicer program.

 

I'd keep experimenting, but there are so many variables it would be a big assist if someone could clue me in as to where to focus.

 

BTW, yes, ABS is the much preferred medium for this application - I don't want to go with PLA. 

 

Anyways, appreciate any advice.

Edited January 24, 2023 by minuteman64
add info I forgot to include in original post

[MariMakes 206]

Hey @minuteman64,

 

There are three settings that jump to mind when I see this. 

 

A. Regular Fan Speed at Layer
B. Number of Slower Layers
C. Bottom Layers (If you use Spiralize Outer Contour it could be the transition between bottom layers and the walls. )

Can you increase or decrease these settings to see the effect on your printjob?

If this doesn't work it might be hardware related. Than it might be your bed level or even your Zaxis. 

[minuteman64 4]

I'll take a look at my settings.  However, .......

 

I've been printing with fan disabled - that seemed to be the abs standard, based on my reading/previous prints.

 

Current setup is for bottom layer at 1/2 speed.  I've had best results at 80mm/s for upper layers which would mean 40mm/s for bottom layer.  Lower print speeds seem to make the problem worse.  I tried a plug-in to print the bottom 10 mm at a lower speed (30 mm/s as I recall) and that was by far the worst print (the shrinkage/distortion extended the entire 10 mm where the speed was reduced).

 

I'm not sure what Spiralize Outer Contour is.  I'm using Cura 3.2.1 - I'll search to see if it is in play.

 

Appreciate the input.  

[minuteman64 4]

Just checked.  Spiralize Outer Contour has not been enabled for any of my test prints.

[minuteman64 4]

I may (after about 10 test prints) be on to a solution.  I had been printing at bed temps 105-110, based on my reading that you gotta keep the bed temp high with abs.  I started dropping the bed temp in 5 degree increments, keeping the other settings constant.  Got a reasonably decent print at 95 degrees and still had good bed adhesion.  

 

I'll next try 90, then 85 and see if progress continues.

[minuteman64 4]

Yep, it was the bed temperature.  Went in 5 degree increments down to 80 degrees.  Got best print at 80, still with good bed adhesion.  This problem solved. 

[MariMakes 206]

Glad to hear. Thanks for the updates 👍

[minuteman64 4]

One additional variable.  I was printing at 80mm/s (mainly because that's what my Cura defalulted.  I accidentally did a print at 60mm/s, all other parameters unchanged, and got a distorted bottom estending 2-3 mm upward from base.  So, for this print, bed temp lower:  good.  Print speed lower:  bad.