SoliForum - 3D Printing Community — so this issue while printing hollow objects

Re: so this issue while printing hollow objects

2015-03-14T20:19:45Z

jagowilson wrote:

Perimeters refers to inner shells, external perimeters refers to outer shells in print settings -> speed.

yes, I'm asking if there's a way to only change the innermost shell only. Those are the ones which don't bond properly, slowing down the speed of all the perimeters will slow down print time too much needlessly.

you don't have to worry as much about bonding issues when your entire perimeter is one thread (extrusion never stops in spiral vase mode). You'd be quite amazed what you can pull off with spiral vase mode.

Hm, I've actually never looked into the spiral vase mode, I've just thought it's a preset for printing 1 perimeter thick vases with 1 perimeter enabled and infill turned off.

I'm not sure how extrusion never stopping (I guess you mean retraction not happening) helps here.
should probably read some about spiral vase printing.
EDIT: Oh, I see.
Cool feature, too bad I can't use it for things which have overhangs.

One thing I can tell for sure from observing the print job is that poor bonding which causes these strings doesn't happen when new layer perimeter starts printing, but randomly.
I'm pretty sure it would go away if innermost shell speed was slowed down, as the bonding fails to happen on sharper corners.
Maybe I should ask Alex for another feature request if Slic3r doesn't allow to change the speed of this separately yet.

Re: so this issue while printing hollow objects

2015-03-14T17:06:02Z

redbarret wrote:

Thanks.
Is there a way to only slow down the speed of the innermost shell in Slic3r? There's a separate option for outermost shells and they are slower by default.
I wouldn't disagree if I was printing with PLA or colorfabb and getting thin "spider webs"
that can be cleaned up but those strings are the whole extruded shell.

Perimeters refers to inner shells, external perimeters refers to outer shells in print settings -> speed.

However IanJohnson's explanation is the correct one. You probably won't get better results than this because the inner layers have no infill to bond with. More heat may help, as he said. Try going up 5c and lowering the inner shell (perimeter) speed.

I probably wouldn't print something like this hollow. Instead id use 10-20% infill. This issue is part of the reason for the introduction of spiral vase mode -- you don't have to worry as much about bonding issues when your entire perimeter is one thread (extrusion never stops in spiral vase mode). You'd be quite amazed what you can pull off with spiral vase mode.

Re: so this issue while printing hollow objects

2015-03-14T09:40:36Z

Thanks.
Is there a way to only slow down the speed of the innermost shell in Slic3r? There's a separate option for outermost shells and they are slower by default.

I wouldn't disagree if I was printing with PLA or colorfabb and getting thin "spider webs"
that can be cleaned up but those strings are the whole extruded shell.

Re: so this issue while printing hollow objects

2015-03-13T15:44:58Z

What that looks to me like, is stringing due to either over extrusion, or lack of retraction.

The reason it appears to be all over the place, is probably due to a setting for random starting spots for each layer.

In Sli3r Print Settings tab, go to: Layers and Perimeters/Advanced, and set Seam Position = Aligned

Re: so this issue while printing hollow objects

2015-03-13T14:07:57Z

Just to add to what Ian said- it is an intrinsic issue with FDM printing and there is only so much that you can do. In addition to wider layer widths and more heat, I would add that I have less stringing issues like this when I slow the print speed down. Moving slower gives it more time to bond before it is pulled as much and tends to result in less stringing.

Re: so this issue while printing hollow objects

2015-03-13T13:50:06Z

That's a challenge of FDM printing. Imagine trying to make that object out of string. While laying down the outline, any tug on the string is going to pull it straight just like that. Plastic doesn't go down like toothpaste, there is enough stiffness within the extruded thread that it gets stretched a little. Where there is a slope, there isn't as much overlap between layers making a weaker bond so the inner perimeter can get pulled loose. To prevent that you need to increase the layer bond. Increasing heat might help, but I think the best thing would be to boost the extrusion width way up so that less of the thread is hanging over empty air relative to its total width.

Re: so this issue while printing hollow objects

2015-03-13T11:53:04Z

Dont think it would be much of problem unless it causes the outside shell to be compromised.

so this issue while printing hollow objects

2015-03-12T19:00:43Z

Notice its only a thing with inner shells.

Stock Solidoodle 4 and slic3r settings.