Extrusion Width Proper Settings

Hi,

I've been using slic3r for quite a while. I've also been using nozzle with 0.4 and 0.5 orifice and I currently using the latter.
Most of the time on my early days of glory with 3D printers, I just used auto setting for extrusion width (by setting 0 of everything) with my 0.4 nozzle. Days passed, along with my steadily increasing knowledge of FDM/FFF, I realized that it wasn't quite right, especially when I was migrating with 0.5.

Theoretically, extrusion width should match nozzle diameter per minimal so that the filament is always squished rather than just dragged thin.
In practical, however, what I got is counter intuitive. Whenever I have my extrusion width in conjunction with the theory via auto-setting or manually setting it to, say, 0.5~0.8, the prints turned into artistic piece of junk with a renaissance style of gaping. But when I set the width to 0.4, or less, it turns better.

I've confirmed the nozzle diameter by inserting thin wire (0.3~0.35), and it still got plenty of room to jog inside. Also, my Z step is properly calibrated (or so) as 3mm high object printed out as 2.7~2.9mm. Okay, it's actually pretty far from what it should be, but it's mainly because the first layer got too squished. Either way, the filament still have room to be squished, but it doesn't.
Regarding print speed, I've also experimented with many different settings, from a sluggish 10mm/s to 120mm/s.

Edit : Forgot to mention. E steps/mm is also good. Been extruding 100mm and i got 100mm+. Filament diameter is also good. Set to 1.75mm while actually around 1.75-1.85. Everything's a bit over extruding actually, but still, not a decent extrusion width.

Edited 1 time(s). Last edit at 09/20/2015 09:38AM by Vashikovich.

I too have no luck setting nozzle tip size to the proper .4mm
My prints are horrible but if I set it to about .45mm it improves a fair bit. Although im also using Cura and not slic3r.

It greatly depends on the layer height. As you said the extrusion needs to be squished, so the height should be lower than the width. The lower the height the more it's squished.

The first layer (ie proper z offset) is also important, if there's over extrusion and there's a build up of material, that is translated into the next few layers as well. So it's important that the first printed layer height is as it was set in the slicer. I usually check the perimeters with a digital caliper.

Another effect that has a large degree of influence on the perceived proper extrusion is backlash. If the infill lines are in pairs, ie two lines squished together, then a gap, then another two lines squished together etc, the x and/or y belts are not tight enough, or there's play in the carriages or idlers, xyjerk or Amax set too high. When this is all good you get perfectly even spacing between all lines, at this point it is possible to set a proper extrusion multiplier, since plugging those line pair gaps will need about 10-15% more extrusion to take place. This usually ends up over extruding the top and smaller surfaces, which are usually at the top, will be overextruded and raise up above the nozzle height.

Backlash can sometimes be hard to spot as the two lines can be squished so hard together they form one line. Slic3r produces infill with a small turn around extrusion against the perimeters, in the center of such a U turn should be a line visible, an indentation so you can see the individual extrusions. If that's not the case you have backlash.

Another factor to a smaller degree is the overlap percentage between infill and perimeter. The U turns of the infill can cause ridges that on smaller surfaces can cause overextrusion. The default in slic3r is 15%, you can try 13.5% or even lower and see if it improves things.

Also note that slicer 1.2.8 and 1.2.9 overextrude smaller infills like in 3mm wide walls. Use 1.2.7 until the issue is resolved.

[SOLVED]

If your printer failed to lay down wide extrusion even at your extrusion width equal to your nozzle size, what you get there is an under extrusion.
Check everything that is associated with it, i.e., filament diameter (including its consistency), extruder driver current (if it's clicking), extruder steps/mm, partial clogging, etc.
Mine was due to insufficient grip on the drive. This led to filament not gripped strong enough and failed to be fed sufficiently into the extruder. Extruder steps/mm was set correctly, extruding 100mm when told so, but only extruder out of PTFE tube into free air. When it was fed into the extruder, it only extruded around 65mm, the rest was chewed up right away and left the drive gear with plastic chips.
I managed to solve this by tightening the extruder idler spring.

Good day to all you, guys