line width

[OUPS65 3]

He,

I am printing with a 0.15mm nozzel and I am a little be lost to improve the print quality.

CURA 4.0.0 recommend to "slightly reducing the line width value could produce a better print".

a/ How does CURA react on the flow if I reduce the line width by 10% ? by reducing the flow by 10% , with no change on the flow ? with ????

b/ why could I expect a quality improvement ?

many thanks for your input.

Philippe

 

[gr5 2,238]

I've printed with 0.15mm nozzle before with good luck.

 

I used 0.15mm for the line width and that worked fine.

 

I was printing very small things and the part wasn't cooling enough (the nozzle touching the part was keeping it hot so it never got solid and was a big gloopy mess).  The solution was to print 7 items (or at least 3!).  This way each item had time to cool while it printed the layer on the next part over.

 

Some people recommend a cooler nozzle temperature also but that didn't help me much.

 

I printed 0.1mm layer height such that the Z resolution matched closely the XY resolution.  That worked quite well.

 

Please post pictures and include part of your finger for scale.  I find coins for scale don't help me much unless I happen to have the coin with me.  I always have my finger with me so I find that to be better for scale.

 

[gr5 2,238]

These were made with a 0.15mm nozzle.  The quality looks crappy until you realize how small they are.  The imperfections seen easily here are not so easy to see without a magnifying glass in real life.  That's not my thumb - that's a finger.

 

I like that you can tell that the closest figure is a man holding a young girl - you can easily see where her knee bends.

 

"retraction minimum travel" defaults to 0.8mm but I should have changed that to 0.1mm for this print to get rid of all that stringing between the other man's legs.

 

Really these do not look impressive in this photo but look very impressive in real life.

 

[OUPS65 3]

Many tks for your answser with your helpfull feedback. Congratulations for yours prints..... We also have to face with the macro pictures distorsions.

We are printing with an 0.15mm nozzel with a layer heigth of 0.08mm. This work well too :

To fix the ideas for the duckboard :  the rectangular holes are 0.36mm x 0.36mm and the solid part between two holes to a width of 0.274mm. His thickness  is 0.374mm. The filament used is a PLA PREMIUM from 3DONLINE.

 

our discussion between us was about the CURA process :

Any idea how does CURA react on the flow if we reduce the line width by 10% as per their recommandations ?

some said that the flow is automatically reduced by 10%, others said that Cura do not impact on the flow  when changing this  line width  setting ?

Many tks

Philippe

 

[randyinla 14]

On 5/18/2019 at 8:09 AM, gr5 said:

I was printing very small things and the part wasn't cooling enough (the nozzle touching the part was keeping it hot so it never got solid and was a big gloopy mess).  The solution was to print 7 items (or at least 3!).  This way each item had time to cool while it printed the layer on the next part over.

So many people take this approach to print out small things or tall narrow things (the robot, for example).  Seems it would be nice to have an option to calculate a layer's area and have the hot end move off of the print for a few seconds to allow the layer to sufficiently cool.  I realize there could be drippage, so not sure if it's a viable solution. 

 

The goal would be to gain the advantage of printing multiple things at the same time to force layer cooling without the wasting of filament when printing two of something.  A wipe tower where the hotend spends much less time on than a prime tower.  Just a simple wipe before moving back over the print. 

 

I was attempting a two-color print yesterday on my U3Ext and tried it without a prime tower.  The first color dripped a few times but the second color dripped every single time it was pulled up and out of the way.  Both were PLA and both had a standby temp of 140c.  I had an AA core in both sides, so it wasn't that a BB core was the culprit of the drippage.

 

As for line width... it's been my experience that setting it slightly thinner than my actual nozzle draws out lines a little closer together.  The extruding seems to be the same and I get lines that are squished more into one another horizontally.  I understand the documentation says that the extrusion is adjusted when the "line width" parameter is adjusted and I've seen people quote gcode showing slightly less or more extrusion.  However, in looking at what my printer spits out (I typically print .1mm layers), a line width setting of say 0.385mm always prints lines that touch each other and leaves no gaps.  Setting line width to .4mm or above (many 3d slicing articles & threads on the Internet suggest always setting "line width" wider than the nozzle, some suggest as high as 120% of the physical nozzle width) will usually leave gaps between my printed lines.  If my part needs to be dimensionally accurate, I'll measure the printed piece and possibly adjust the horizontal expansion and print again until it's exact (though material shrinkage plays a huge part in this as every filament can shrink more or less).  But mostly, I just reduce the line width a bit and end up with perfect prints. 

Edited May 23, 2019 by randyinla

[Link 34]

i have done a fair amount of testing with different line widths and repeated those since my S5 arrived, the thinner line widths used by default in Cura in general are not as good for overhangs, the thinner line width can lead to poor bonding on overhangs and some stringing. I have also seen lines not bonding together and leaving gaps with thicker line widths as mentioned above, however i have also seen this on the default thinner widths, so its not 100% that thinner prevents this issue, I think there is some sort of Cura quirk with gaps in perimeter lines and it seems to come and go. 

 

In terms of print quality i have found a slightly thicker than nozzle line width gives much nicer prints overall, esp on overhangs, I then increase the infil and wall overlap percentage to add some extra squish to remove any potential gaps. I also found that perimeter gaps were often present after a combing move if the combibg move was quite long and the nozzle pressure dropped, be sure to set the max comb travel with no retract to help prevent this

 

Also gaps between perimeters can be very much material dependant, for example some PLA's do not have as good layer bonding properties as others and these tend to leave gaps more as the plastic shrinks as it cools and pulls the lines apart.

Edited May 21, 2019 by Link

[yellowshark 153]

What has not been mentioned is setting your line width to what actually is extruded rather than the physical specification; i.e. what comes out of the nozzle not what gets squished onto the build plate. I have been running a nozzle and line width for some time now of 0.45 having checked this. Lol it works for me.

[Link 34]

34 minutes ago, yellowshark said:

What has not been mentioned is setting your line width to what actually is extruded rather than the physical specification; i.e. what comes out of the nozzle not what gets squished onto the build plate. I have been running a nozzle and line width for some time now of 0.45 having checked this. Lol it works for me.

 

Not sure I follow this logic, the first layer will be wider than you specify due to the squish into the build plate, subsequent layers should be as per what you set the line width to (assuming the nozzle is the size you specify and esteps are correct etc) the slicer calculates the flow etc to achieve your specified line width. 

 

If you are saying you ask for a 0.45 width with a 0.40.nozzle, but actually get a 0.35 for example, then change your line width to 0.35 likely the end result will change again as the slicer will reduce flow etc to get were it thinks it should be. You will be chasing your tail forever ?. Unless I am missing what you mean here ?, Are you saying you actually measure the nozzle diameter?

Edited May 22, 2019 by Link

[yellowshark 153]

My point is that the rated size of my nozzle is 0.4. So unsurprisingly in Cura I set my nozzle size to 0.4 and line width to 0.4. But at some stage, about a year ago, I checked this and found that my nozzle size was 0.45, wear and tear? Or to be more accurate the width of the filament flowing out of the nozzle with a manual feed was 0.45. So I set nozzle size and line width to 0.45 and improved my results

[Link 34]

Interesting, How did you measure the nozzle, some sort of optical method ?

[yellowshark 153]

No I measured the filament flowing out, not the physical hole. I.e. I manually fed filament from the nozzle, using Repetier Host printer control software which provides the capability, cut the filament off and measured it with a digital calliper; which I did several times to check consistency.

[randyinla 14]

No matter the extrusion pressure/amount, if you are just letting the filament come out into air and measuring that, it "should" always be the same width, which I'd imagine is the width of the nozzle.  If the extrusion goes up, it'll just come out faster.  It's when the line is actually printed onto a surface that the width could be affected.  The speed of the hotend movement PLUS extrusion amount/rate will change the width of the line when printed onto something, whether onyo the glass or a previous layer.  Pushing a lot of filament out of the nozzle onto a surface but moving the hotend very slowly will make a wider/thicker line than pushing a lot of filament out of the nozzle and moving the hotend very fast.  Also, the layer height is a factor.  And pushing too much in relation to height and speed of the head can cause it to pool up around the shape of the nozzle, creating a "U" shaped line instead of a flat "_" line when viewed from the line's end.

[yellowshark 153]

Well I suppose everything you say, under certain circumstances, is correct. BUT if your printer is setup correctly and your slicer settings are correct/optimum, then you are wrong. Under these circumstances if your nozzle is physically 0.4mm and you have specified line width as 0.4mm then that is what you will get; it does not matter what layer height or print speed you are using. If the line width were not 0.4 then you would not get a perfect finish and would probably get some minor dimensional errors.

 

One caveat; the faster you go the less accurate you become and the lower quality you get. This is not something I have researched but I had always figured that was a mechanical issue. Somewhat like a car going around corner, the faster you go the more understeer you get, assuming the car has been setup to understeer which is the case with all family/saloon cars etc.

 

 

[geert_2 558]

15 hours ago, randyinla said:

No matter the extrusion pressure/amount, if you are just letting the filament come out into air and measuring that, it "should" always be the same width, which I'd imagine is the width of the nozzle.

 

Originally, I also thought so. But I got inconsistent results when measuring these extruded strands: they could be anywhere between 0.40 and 0.60mm. So, something was off, but I didn't know what.

 

Later I saw a Youtube-video of "nozzle-developers" (I don't remember from which company), and they said this very common assumption was not true. When the plastic comes out of the nozzle, it is still molten. Molten strands of plastic usually have a strong tendency to contract. This is because during extrusion their very long molecule chains are stretched. These chains are then under a very high stress. When that stress falls away (=as it exits the extruder), the molecules tend to relax to their previous shape. So the strand gets shorter and wider. At least, as long as the plastic is still molten. This effect is similar to when you heat most plastics in a flame or with a hot air gun. Especially for thin rods that have been extruded or injection-moulded under high pressure. The width of the rod expands, but the length contracts. I haven't discoverd this, I am just echoing their findings.   :-)

 

After watching that video, I tried this on my UM2 printers. I manually fed material through a very hot nozzle (with bowden tube removed). When pushing hard, I could get sausages of up to 0.8mm to 1.0mm, out of this 0.4mm nozzle. When extruding manually at very low temperatures, barely above melting temperature, and at very low speeds/pressures, the expansion is far less, and I usually got to ca. 0.45mm.

 

So you can not use the extruded sausage-diameter as an accurate reference of the nozzle diameter, only as a crude estimation. A better way to measure the inner diameter might be to use copper wire strands, clean the tip (often deformed after cutting it), and then try which ones fit into the nozzle. And then measure the width of these strands with calipers.

 

I have grinded down a soft steel injection needle, and use that. I made it for the purpose of cleaning, but I also used it for measuring. The needle tip of 0.39mm could easily get into the nozzle opening, but a bit further where the needle was still its original 0.41mm, it could not get into the nozzle anymore. So, given the +-0.01mm accuracy of my calipers, and my imperfect sanding of the needle, nozzle opening was quite accurate. Today, a couple of years further, the same needle easily goes up into the nozzle all the way, and it still has some play at 0.41mm, so the nozzle has worn out a bit.

 

If you mathematically want to calculate volume, when feeding electronically via the feeder, you also have to account for the partial slipping of the feeder wheel. The feeder bites into the filament and deforms it. At low speeds and low pressures, these are nice square indents. But at higher speeds and pressures (=more mechanical resistance), the feeder has to push much harder, and instead of squares, these indents become stretched, long diamonds. You can see this deformation under a microscope. So, the effective amount of fed-through material is less than calculated, due to this "partial slipping". To compensate, you need a higher flow-rate.

 

Due to the huge amount of other variables involved, I wouldn't know how to accurately predict or calculate all this. So I use the good old and proven, "trial and error", and use that experience as stable starting point. Any method that gives good results, is a valid method.   :-)

 

 

What I often do for new materials (but you could also do it for new nozzles), is remove the bowden tube and manually feed some material through the nozzle. Then I adjust temperature on the fly, and watch and feel how it melts and flows. This gives me some feeling for the material (or nozzle). Then I print a couple of test pieces, starting from the default values, and on the fly I adjust speed, temp, flowrate up and down, to get an idea of the edges up till where it still works fine, and where it starts to go wrong.

 

[geert_2 558]

On 5/20/2019 at 11:53 PM, randyinla said:

...

Seems it would be nice to have an option to calculate a layer's area and have the hot end move off of the print for a few seconds to allow the layer to sufficiently cool.  I realize there could be drippage, so not sure if it's a viable solution. 

...

 

This option exists in older Cura-versions, with the "minimum layer time" and "cool head lift" options. I don't know if it still exists in new versions?

 

I tried this, but it did not work very well for me. The problem is that if the nozzle is simply moved away while waiting, the filament gets hotter and more liquid in the nozzle. So it starts leaking more, and the more liquid plastic flows differently upon starting the next layer. Further, the added heat during this waiting period, also has to be removed in the cooling cycle, so it does not really help very much. Any differences in layer printing time, or in molten filament temperature, show up as horizontal lines and deformations on very small objects.

 

In my experience, you need a very constand flow rate, constant temperature, and thus constant layer area, for best results. But the nozzle needs to be away from the object long enough, so it has time to cool down.

 

So, we need to print multiple models at the same time, or print a "dummy cooling tower" next to the real model. Ideally, this dummy should have the opposite layer-area as the real model, so the total area per layer is constant for the whole model. This is especially true for very small models, with 100% infill, and thus a lot of stored heat which has to be removed. When models get bigger, this is no longer required, as each layer gets enough cooling time anyway.

 

See these pictures I made a few months ago:

 

 

 

[geert_2 558]

I didn't know I had a photo of the above effect: expansion of the molten filament after exiting the nozzle. But I just stumbled upon it again, so here it is.

 

You can clearly see how the sausage expands immediately after exiting the nozzle, during the first mm. In the zoomed-out image the sideways expansion is from ca. 46 pixels to ca. 51 pixels, thus about 10%, very rough estimation. Nozzle opening is 0.40mm, so that would be from 0.40mm to ca. 0.44mm.