Flowrate for solid infill?

[Hobsie 0]

When my printer does solid infills it often feels like it is over extruding (plastic bunches up rising above the tip of the nozzle).

However, when measuring the thickness of walls my measurements suggest that it's under extruding (walls slightly thinner than line width). For top layers this often results in a rough solid infill and the occasional gap between infill and walls. In fact, if I dial back flowrate until the solid infills look good I can end up with a flow rate of 85-90% (when measuring my wall thickness would suggest I need ~104%). I do check filament diameter but this happens with many different filaments (and tbh filament diameter consistency seems pretty good these days)

Those gaps can be closed with bigger overlap values but I'm not finding any settings to control either the infill overlap between infill lines for solid infills or just general flow rate for infills or solid infills - modifying these would seem like a simpler option.

 

Are there any settings like that in Cura I could use to get better control over solid infills? I'm currently using Cura 3.3.0.

[smartavionics 289]

Hi, what speeds are you using for the infill and the walls? Most extruders tend to underextrude as the speed increases so if you are printing the walls much faster than the infill then they will come out thinner.

[Hobsie 0]

Thanks for responding smartavionics.

General print speed is at 60mm/s but I believe the speeds that are really relevant here are the outer walls at 30mm/s and the top/bottom speeds (what I've been calling solid infills) are also 30mm/s. I can try normalise those speeds to see if it makes a difference but it feels atm as if there's something awry since there's such a significant flowrate difference from walls to top/bottom layers (solid infills)

[smartavionics 289]

OK, the speeds are similar so it's not that. Could you please post some gcode that you know has this problem and I will see if I can spot anything else that could make a difference.

[Hobsie 0]

Well I decided to try a bunch of speed values and that had an immediate effect on the quality of top and bottom layers - in fact slowing down to 15mm/s for the top/bottom layers has virtually eliminated the over extrusion!

 

I've uploaded a test print using 15mm/s for the top/bottom layers and it's come out pretty good! Still a little bit of gap between the infill and walls but at least things have improved.

 

Thanks for the input smartavionics

Edited May 12, 2018 by Hobsie

[eldrick 62]

Printing the solid infill at 90-95% fill will correct issues with overextrusion by giving any excess material somewhere to go.

[Hobsie 0]

@eldrick is that actually an option for bottom and top layers though? (Which is what I’m calling solid infill) I can’t seem to find that for them.

[eldrick 62]

No, and top/bottom aren't infill, they are walls, so they get the same extrusion as other walls, although you can separately set the number of top and bottom layers.
Slowing down the speed should work for what you are asking, and for top layers, you might look at the Ironing settings for even better top quality. 

[smartavionics 289]

1 hour ago, eldrick said:

No, and top/bottom aren't infill, they are walls, so they get the same extrusion as other walls, although you can separately set the number of top and bottom layers.

 

No, top/bottom aren't walls, the're top/bottom (aka skin). The top/bottom can have different line width and speed to the walls.