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james-newton

Size of smallest printable line?

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How do I find the size of the smallest "trace" or "cube" or "line" that I can print? That will not be dropped out by Cura when it makes the g-code?

E.g. If I want to print a mesh, like a screen, or a grill, or a sieve. How small can I make those lines in the .STL file so that it actually prints them?

Is there a setting that controls how small an object it will try to print?

As a specific example, I made an customizable stencil / silkscreen mask script for OpenSCAD:

http://www.thingiverse.com/thing:276815

http://www.thingiverse.com/apps/customizer/run?thing_id=276815&code=5d95f16abc40e910514a4be085658ca0

And when I use a "grid thickness" of 0.2mm or even 0.3mm, those grid lines just disappear in the layer view.

 

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Hi,

with a standard .4mm nozzle, I can print good 0.3 shell thickness lines/walls.

In stl's walls have to be thicker than the in cura set shell thickness otherwise they will be skipped.

Circular or curved lines have to be somewhat thicker, because of the 'facets' {resolution) in the design.

for more detailed prints I use a 0.2 nozzle somewhere out of china I guess.

 

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This seems to change with different versions of Cura so I would experiment, but typically it can print down to your nozzle diameter. So if you set the nozzle diameter to .4mm it can typically print down to .4 or maybe .41mm (walls can get thinner on curves with less than infinite edges?)

You don't have to edit the model in cad each time. You can scale your part in Cura or you can play with nozzle width until you find the formula for thinnest wall versus nozzle diameter. Shell thickness setting *might* affect things also but probably not.

 

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Thanks! It's the " shell thickness" setting in Cura that makes all the difference, no matter the machine Nozzle diameter. That is, at least as far as what it /tries/ to print. I'm not saying I can actually print a finer line, but setting the shell thickness to anything less than the size of the lines causes them to show up.

 

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If you set shell thickness to less than nozzle width then it purposefully underextrudes. This is acceptable down to about 75% (shell 0.3mm) anything lower and you get ugly underextrusion and weak layers. And holes.

 

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This is quite interesting stuff, however I would also like to know the opposite.

What is the smallest gap that can be printed?

If I print a line with a series of small breaks, what is the smallest gap that will / can be printed?

 

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There should be no limit to how close two parallel lines can be. Although temp/speed/acceleration will affect the flow so when the gap is 1/10 of the width of the nozzle (.04) if you over or underextrude by 10% it will fill or double that gap. However PLA shrinks as it cools and if it touches it will stick so if the PLA wall misses the other PLA wall by a micron it will then proceed to shrink by about 10% or .02mm on each side of the laid down trace of PLA. So I guess gaps of smaller than .02mm are impossible without getting a smaller nozzle drilled out.

For breaks in a wall (like windows) there is also theoretically no limit but this is more difficult - especially if the slicer decides to bridge that gap with a non-extruding move because the extruder is not good at stopping. So if there is a non-extruding move I would say off the top of my head that gaps thinner than .5mm will be difficult. In fact you probably want to put a larger gap than desired into cad. But if you can get the slicer to approach the gap and leave the gap from the same side then the limit is to keep it from touching and how much PLA shrinks (around 10% from liquid stage maybe) - .1mm should be no problem. .04mm would be around your limit but very difficult because the liquid PLA bead will shrink about .02mm on each side. Any closer and the PLA will fuse and there will be no gap.

 

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Thanks for the comprehensive reply, it is very helpful.

The question wasn't idle speculation, I have a design I am working on that requires small gaps in the line.

I have begun to experiment.

What I am modelling is a wall clad with veritical wooden boards. So on one side of the wall there are a series of small vertical grooves running up the wall to represent gaps between the boards.

I tried three sizes last night.

0.5, 0.4 and 0.3 mm wide square grooves.

All 0.2 mm deep.

Printed with PLA, 0.2 mm layers at 50 mm/s.

No pictures yet (I'll post some if I can work out how to take some that actually show anything useful)

All three gave visible grooves. The grooves weren't square, they had been partly filled in to create rounded grooves.

The depth decreased as the width decreased.

0.5 mm essentially worked.

0.3 mm was almost compleatly filled in although you can feel a ripple

To get this design to work it is clearly going to be a case of finding the right combination of width and depth of the groove

For my use I will probably use 0.5 mm wide and 0.2 mm deep, although I might try deeper grooves.

 

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You will get sharper/better results when the fan is at 100% yet the default settings I believe don't have the fan come on until 5mm above the bed. Also you will get sharper/clearer results at slower printing speeds such as 30mm/sec.

I recommend you put all the different combinations to test on a single test piece and print them all at the same time.

 

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About the original topic:

I think this can be considered a bug in cura 14.03.

I've been trying to print a very thin wall. Anything above 0.4mm gets printed fine, but anything below gets skipped in the layer cutting.

The bug is in the relationship with the wall thickness - the 0.41mm wall will be skipped if the wall thickness is higher than 0.4, but once it gets to 1.2 it's not skipped anymore. Why is this?

And in general, why are these tied together? If I need a thin wall in one place but I don't want the whole part to have a super-thin shell, what am I supposed to do?

J.

 

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I've been trying to print a very thin wall. Anything above 0.4mm gets printed fine, but anything below gets skipped in the layer cutting.

 

Good so far. You can't print a wall thinner than the nozzle of course.

 

 

The bug is in the relationship with the wall thickness - the 0.41mm wall will be skipped if the wall thickness is higher than 0.4, but once it gets to 1.2 it's not skipped anymore. Why is this?

 

What? Can you rephrase this? This

1) doesn't sound like what cura doeas

2) I'm not even sure what you are trying to say.

 

I've printed .41mm thick walls using cura set to .4mm nozzle size. But what happens at 1.2? What? I don't understand.

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And in general, why are these tied together? If I need a thin wall in one place but I don't want the whole part to have a super-thin shell, what am I supposed to do?

 

You can set shell thickness to whatever you want. I've even set it to 100mm and it will fill solid with concentric fill instead of diagonal infill.

So if you set shell to 1.2mm and nozzle to .4mm then it will will print .4mm walls just fine and 1.2 walls also solid.

If the wall is thinner than "shell" setting it does fewer passes.

 

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Well you can lie and say that the nozzle is .3mm and Cura will act just like it is a .3mm nozzle and underextrude appropriately and put the lines closer together and such. It might, kinda work. I don't recommend it.

 

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Hello, I have a problem with the size of some objects. With Cura I was able to print out a coin, with the spheres with a diameter of 0.9 mm. I tried to print an object with a written 3mm Cura but does not recognize it. Do you have any advice?

I have a Witbox with 0.4 mm nozzle.

Thanks%5C%5CPrincipale%5C3d%20works%5CLavori%5CLavori%20commissione%5CMarchio%20Movimento%20degli%20arcani%5CTest%20AE.jpg

 

http://i61.tinypic.com/6y1mww.jpg

 

http://i60.tinypic.com/2cqnqk7.jpg

 

http://i57.tinypic.com/9i4vvn.jpg

 

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It might *not* be the size. It might be something else.

Look at the model in XRAY view (instead of layer view). If you see *any* red then there is a problem with the model. You can fix the original model with CAD or you can try the 11 combinations of "fix horrible" (don't click both A and B).

 

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In the first image, that of the coin, there are spheres with a diameter of 0.9 mm and I printed. I'm sure! While in the other images of the letters are 3mm and not print at all. It 'really strange.

Now I did a test with these L. As you can see the size is 14.5 x3x2mm. In the x-ray view there are no errors but still does not print correctly.

http://i62.tinypic.com/35bwok4.jpg

http://i58.tinypic.com/izuxxk.jpg

http://i62.tinypic.com/j13w4x.jpg

 

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Good so far. You can't print a wall thinner than the nozzle of course.

 

What? Can you rephrase this? This

1) doesn't sound like what cura doeas

2) I'm not even sure what you are trying to say.

 

I've printed .41mm thick walls using cura set to .4mm nozzle size. But what happens at 1.2? What? I don't understand.

 

yes, I agree, that was very unclear, and probably had an error or two. Only now had time to check up on this thread...

my issue was with a thin wall, i was trying to create a pocked for a magnet and use the thinnest wall possible.

below 0.4mm cura skipped it, didn't slice it. i think it was the same for 0.4mm.

then at 0.41mm... *pause to rerun tests with simple part*

ok, something is very wonky here.

see image link below. this part has a 0.41mm wall on the right, and 0.4 on the left (same for slats, but those i'll ignore right now). i tried values from 0.3 to 1.2, and at various stops either one or both walls were skipped (0.41 less often).

that's what i was trying to say in that prev post, but then i also thought it might be multiples of 0.4, but no, it's kinda random... 0.7 shows both walls, so does 0.69, and 0.8, but 0.9 is missing both... etc.

hmmm....

http://i.imgur.com/PgJaLZl.png

 

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I think what dimensioneer is saying is that you can do "fix horrible A" and it will fill in the entire cube, then turn off infill (set to 0%) and set shell thickness to 0.4mm.

This should get you what you want if the object is *very* simple (e.g. no holes).

 

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I think what dimensioneer is saying is that you can do "fix horrible A" and it will fill in the entire cube, then turn off infill (set to 0%) and set shell thickness to 0.4mm.

This should get you what you want if the object is *very* simple (e.g. no holes).

 

That seems like a quite a workaround. Should I open an issue for this?

 

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