Slicer problem? Or just 3D Printing Limitation?

In trying to determine the smallest text that could be printed and the smallest relief (extrusion?) required for it to be legible, I generated the *.stl below to test the limits of what it could print. 2mm, 3mm, 4mm, 5mm at 0.5mm, 1.0mm, & 1.5mm extrusion heights.

I printed one version lying horizontal and one vertical. I discovered after I printed the 2mm didn’t have a single print; the 3mm had garbage; and the 4mm & 5mm had some printing that was fairly readable. Surprisingly, the vertical seemed better quality!

I changed the setting to print “High Quality” thinking it’s the layer height. Then I generated the gcode and noticed the gcode image on the screen matched the printed sample from the “Fast Print” mode.

I thought “A-ha”!!! The Luban slicer can’t handle the small sizes. So I downloaded the Cura slicer, ran the gcode against the same stl file, and lo and behold . . . the exact same results as Luban (at least they looked visually the same).

So, can someone provide some insight here? Does Luban slicer have any user setting that allow for finer granularity? Higher fidelity? Or am I asking the slicer and printer to do things that are physically impossible to do?

For anyone interested, here is the stl file for the work-piece.
Extruded Text Test v0.4.stl (2.6 MB)


A slicer is always trying to figure out how best to reproduce the stl provided. It’s always a bunch of compromises and interpolations. Sometimes this can result in some pretty strange (and sometimes cool) errors.
It doesn’t know what to do with items smaller/thinner than it can print.
So it just doesn’t even try. It just eliminates those portions and/or averages it out.
If you look at the preview once you run g-code in Luban it’s showing exactly the same results as what your printing.


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I was curious, so I tried slicing the data with Cura.

On the contrary, the result seems to be as per the slicing.

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The main issue you are showing are slicer settings:

I guess there would be a similar option in cura about “allow sinlge wall extrusions”, there is also a need of minimum extrusion length and minimum extrusion width.

You have to play a bit with the settings :wink:

Just to state the problem explicitly, Cura & Luban know that your print nozzle is 0.4mm wide, and they will not print any line that is narrower than that. Cura might have some settings (in theory, a slicer could deliberately under-extrude to print a narrower line), but I’m not seeing anything obvious.

The 2mm tall font is small enough that all of the lines are smaller than 0.4mm. The 3mm font only has a few spots where the lines become wide enough. The font choice would affect this. For example, a block letter font should work better than an ornate font.

You might experiment with insetting the text rather than that exposing the text. The slicer can leave gaps that are much finer than the 0.4mm nozzle setting. Before you play with it though, I’d suggest getting your extrusion settings dialed in. Over/under extrusion will cause problems if you want to leave a very fine gap.

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i assume a smaller nozzle size would help…
is this true or advisable?

Yes, you are right.
You need a other Slicer than Luban for this.

Yeah smaller nozzle will work, the if you try to put tell the slicer you have a smaller nozzle and simulate the print you will see how it thinks it will come out with that smaller nozzle size too

I started looking into this and decided it wasn’t worth it to me.
(Try a google search for ‘smaller nozzle 3d printing’ for more info.)
There are trade-offs for smaller nozzle size.
One being much slower. Another just a lot more finicky on settings.
From what I read it seems that you don’t quite get as much more resolution as you’d expect in real world use as you would think.
If you do try one, make sure you’re using really good filament with high tolerances like Prusament.

After many hours and many tries, I have come to the following conclusions:

Font matters - Arial isn’t that good, Arial Round Bold is better, Old Sans Black is even better. There might be an even better font, but I’ve reached the limit of my patience to find out.

Font size isn’t font size - I tried the best I could to size the fonts at 2mm, 3mm, 4mm, and 5mm . . . it turns out, the font size needs to be manually adjusted in some cases.

Printing vertically tends to have better results than printing flat (horizontal). This was counter intuitive for me. I would have bet the bank that it would be the other way around.

Printing relief text in the vertical plane is slightly better than printing extruded test in the vertical. (completely subjective evaluation).

An extrusion or relief of 1mm is most likely sufficient. Anything more or less is less defined.

Here are my files and photos of finished products. Use the stl files to your heart’s content.

Extruded Text Test v0.4.stl (2.6 MB) Relief Text Test Arial v0.2.stl (2.6 MB)

Arial Round Bold
Extruded Text Test Arial Round Bold (1.1 MB)
Relief Text Test Arial Round Bold (1.7 MB)

Old Sans Black
Extruded Text Test Old Sans Black v0.1.stl (3.6 MB)
Relief Text Test Old Sans Black v0.2.stl (2.7 MB)

For the suggestion to go to a smaller nozzle . . . I’m not that committed yet! :slight_smile:

Let me know if I missed anything.



These gaps are a slicer problem. S3D would fill those in with the right settings. I’m sure Cura can too, but I’m not sure the correct settings for that. I also know that PursaSlicer can deal with that.

Also, rather than printing that out to find out there’s issues, the gcode preview will be able to show you if there’s gaps or not (at least in S3D).

The resolution is asymmetrical. In the X/Y direction, the smallest feature is the nozzle size, even though the nozzle can be positioned more accurately than that. In the Z direction, the smallest feature is the layer height.

But 3D printers can’t print in empty air very well. Printing outset text vertically usually means you’ll need support, or you’ll loose the first couple of layers to spaghetti (you likely have some small nubs of filament hanging off the bottom of your text). Printing inset text vertically should work better, because there is material for the printer to bridge (but you might see some loose of definition on the top of letters).

That’s true… if you’ve got the printer calibrated well. But the part of the picture you zoomed in on does look more like a slicer issue than a calibration issue. In that case, it seems that the fill between the letters is smaller than 0.4mm, so the slicer didn’t fill it in. That should show up in the preview.