Vase mode solid bottom offset

[Samon 0]

Hello everyone! This is my first post so please don't beat me ?

 

I'm trying to print a model (upside down from STL file ) in vase mode with solid bottom layers.

The problem is that after adding bottom thickness the model surface is no longer continuous,

there appears a step - see the photo ( preview in S3D because Cura does not show it ).

 

Could you help me get rid of the step?

( I removed everything from config folder, set up nozzle, layer height, spiralize and bottom thickness )

 

Thank you !

 

flat.stl

Edited July 31, 2018 by Samon
Added stl file

[burtoogle 513]

Hello @Samon, the spiralize mode starts the spiral wall after the bottom layers have been printed. The first spiral layer starts at the same height as the last bottom layer so at the very beginning of the spiral the filament will squish out as the effective layer height is zero at that point. By the time the first spiral has completed, the nozzle will have been raised by 1 layer height. So you will always get some extra filament around the first spiral layer. Ugly? Yes, but it does increase the likelyhood of the printed object being waterproof.

[kmanstudios 1,120]

I am thinking that you could try the "Initial Layer Horizontal Expansion" Set to a negative number. It seems the effect you are getting is 'elephant's Foot' and that was designed to offset that. Give it a shot, it may help.

[burtoogle 513]

4 minutes ago, kmanstudios said:

I am thinking that you could try the "Initial Layer Horizontal Expansion" Set to a negative number. It seems the effect you are getting is 'elephant's Foot' and that was designed to offset that. Give it a shot, it may help.

 

Unfortunately, that won't help here because the elephant's foot is not occurring on the initial layer but on the first spiralized layer. It's a Cura bug (or feature) depending on how charitable you are feeling. An obvious solution would be to reduce the flow at the beginning of the first spiral line and gradually increase the flow as the wall progresses. Unfortunately, doing that requires very small extrusion amounts to be used at the start of the spiral and would, in all likelyhood, not produce a reliable watertight bond between the spiral and the solid layers below. It would be very annoying to spend many hours printing kgs of filament only to find that the resulting object leaks out of a tiny hole at the start of the first spiral. Perhaps a reliable solution that produces less of a bulge would be to start not at 0% flow but, say, 30% flow and increase the flow to 100% as the first spiral layer progresses. That would reduce the bulge but, hopefully, still make a reliable join.

[kmanstudios 1,120]

2 hours ago, smartavionics said:

Unfortunately, that won't help here because the elephant's foot is not occurring on the initial layer but on the first spiralized layer.

Thanks for the correction ? always good to learn proper things

 

2 hours ago, smartavionics said:

bug (or feature) depending on how charitable you are feeling.

?

 

 

[ftoons 5]

 

 

Its Sept 2021 and the problem is still present. 

id like to clarify that the large layer/s are actually the bottom layers, not the first spiral layer. 
I’m printing vases and if I have 3 bottom layers I see the 4th one (the first spiral layer) smaller in diameter from the outside of the model. Layers are all smooth from the inside.

it is as if the line width of the spiral layers is smaller, or as if the inner wall of the bottom layers is pushing those bottom layers slightly out. 
tried decreasing line width and flow rate of the inner wall, didn’t help.

the second and third layers are not “first layer” anymore so can’t control them with that.. 

only if there was a way to remove the inner wall, or to decrease the line width of the bottom layers!!

[ftoons 5]

I think I found the culprit. 

Its the "Smooth spiralized contour" button that is causing the spiralized part to shrink a little. So the lower layers are actually not protruding out, rather the whole upper spiralized part that is going a bit inwards.

 

I hope this would be fixed at some point in the future, so that the whole vase prints smoothly without any bulges.

[gaduffl 0]

This should really be solved. With high extrusion rates and more overhang it makes vase mode basically unusable since the layer offset is so huge.

[marlbresen 0]

Has this been solved yet? Its really annoying especially with big nozzle diameters the offset is very visible.