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Slic3r -- default extrusion width?

Posted by MrBaz 
Slic3r -- default extrusion width?
March 28, 2017 10:50AM
Trying to calibrate in Slic3r. If I print a thin walled, single-perimeter calibration square, what should the thickness measurement be?

0.4mm nozzle
0.2mm layer height

Right now, with a modifier of 0.96 for 1.75mm filament (filament easures 1.72mm), I'm getting 0.65mm wall thickness. What does Slic3r say this measurement should be?

Edited 2 time(s). Last edit at 03/28/2017 10:51AM by MrBaz.
Re: Slic3r -- default extrusion width?
March 29, 2017 07:11AM
Either set an explicit extrusion thickness (e.g your nozzle diameter) in "Print Settings"> "Advanced" instead of leaving it as default, and/or examine the generated G code with a text editor - the extrusion thickness that Slic3r has set is stated in the comments at the start of the G code file.

Dave
Re: Slic3r -- default extrusion width?
March 30, 2017 12:11AM
Did you calibrate the e steps? I recently had a similar problem, it didn't help 100% (for my problem, at least) but still you should have done this -> [zennmaster.com]


bq Prusa i3 Hephestos - Print Bed Expansion Kit - Igus RJZM-02-08 - TMC2100 - Heatbed MK2a 200x200 + SSR - Netzteil Dell DA-2 - Repetier & Slic3r 1.33.8
PLZ: 97xxx
Re: Slic3r -- default extrusion width?
April 02, 2017 02:59PM
I did have all of my extrusion widths set, but that is what caused the slicing problem. I have also calibrated my esteps.

I've since just decided to let Slic3r do everything and calibrate using trial and error until best-fit. I have a 0.4mm nozzle, but I changed the setting in Slic3r to 0.35mm nozzle so that the lines are laid closer to each other. I've also disabled gap-fill. I think gap-fill was causing most of my problems.

Edited 1 time(s). Last edit at 04/02/2017 03:00PM by MrBaz.
Re: Slic3r -- default extrusion width?
April 03, 2017 04:29AM
Changing the nozzle size does not directly affect anything - it just causes Slic3r to use a different default extrusion width for everything. Instead of changing nozzle size, you can input your own values for just the perimeter widths, which will result in faster infill (because Slic3r will still use the wider width for that), though that will not fix the original issue.

In fact the single wall test is not at all a good way to set the extrusion width. The issue is that an extrusion that is not bounded on both sides will not be square, but will bulge in the middle so always being slightly wider than the width that is set because Slic3r effectively prints a wall that has an *average* width of what is set, with the ridges of the layers being wider and the valleys of the layers narrower. The wider the extrusion width, the greater the effect, which is why decreasing the width diminishes the difference.

To get a better check, print two solid cubes, one with 100% infill and one with 90% infill. Set zero top layers or stop the print after a few layers of infill have been printed, and examine the surface of the infill under a strong lens or microscope. You should just be able to see gaps between the lines in the 90% infill, and there should be no gaps or significant valleys in the 100% infill. If there are no gaps in the 90% infill you are over-extruding, and if there are gaps or deep valleys between lines in the 100% infill, you are under-extruding. You'll see it better if you are able to change the colour of the filament for the last layer of infill printed.

Dave
Re: Slic3r -- default extrusion width?
April 03, 2017 07:38AM
I've started from scratch and gone a whole different direction.

I'm back to manual extrusion widths. I've dialed everything in so now I have perfect perimeters (near seamless -- no gaps between perimeters). Now having done that, the solid infill and top infill are slightly over-extruding. Options?
Re: Slic3r -- default extrusion width?
April 04, 2017 04:48AM
As a guess, I'd say that you have thin walls that are not an exact multiple of the extrusion width, which cannot be printed without a gap except by using the gap fill option which I think is buggy. You have increased the extrusion rate so as to fill that gap, which is accomplished by over-extruding.

The extrusion rate is best adjusted using solid and 90% infill as I suggested. Then to achieve a gap-free thin wall, set up a perimeter extrusion width that is just a tad less than an exact factor of the wall thickness (or adjust the design to make the wall an exact multiple of the default extrusion width). e.g. if you have a wall that is 1.6mm wide, set a perimeter extrusion width of 0.39mm (i.e. a tad less than an exact factor of 0.4mm - wall consists of 4 extrusions), or 5.3mm (i.e a tad less than an exact factor of 5.3333333mm - wall consists of 3 extrusions). Making it a tad less prevents rounding errors in Slic3r failing to lay down enough extrusions.

Globetrotter
Re: Slic3r -- default extrusion width?
April 04, 2017 03:46PM
I've found decent results with 0.5mm default widths for everything but the Solid and top infill--set to 0.6mm. Not perfect, but acceptable.
Re: Slic3r -- default extrusion width?
April 05, 2017 04:15AM
Quote
MrBaz
I've found decent results with 0.5mm default widths for everything but the Solid and top infill--set to 0.6mm. Not perfect, but acceptable.

That's what I usually use as well (in fact I set it to 0.49mm to prevent rounding errors). I set the top & bottom infill to that width as well as it gives a slightly smoother finish that the default, thicker width (but makes Z homing a tad more critical). But as said, it really depends on the thickness of the thin walls on the part you are printing. For my own designs I always make the walls a multiple of 0.5mm, but if printing someone else's design I may have to adjust the extrusion width to suit the thickness of the walls in that design.

I recently downloaded & tried the latest Prusa version (1.33.8), and that appears to fill gaps less than the extrusion width OK, so it's possible that with that firmware version it will no longer be necessary to change the extrusion width to suit the walls. If so I'll be a happy chappie!

Dave

Edited 1 time(s). Last edit at 04/05/2017 04:17AM by dmould.
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