Ultimaker 2 default nozzle size is 0.46 in Cura

[cloakfiend 995]

So now with my ob installed a while ago, using cura 15.04.02 should i be using a different setting to 0.4 for my nozzle (such as 0.46?) or am i missing something.

[yellowshark 153]

OK I will incorporate that into my next test, certainly as you say, every bit helps .

What exactly is Z scaring?

Also if I set the nozzle width to .35 should I set my shell thickness to 0.7 instead of 0.8? Is this good if my hardware nozzle is actually 0.4?

How does this stuff affect the dimensional accuracy? I assume that whatever I set the nozzle thickness to, within reason, if my nozzle hardware is 0.4 I will still get a line that is 0.4 wide. Where does the missing or excess material go to? Or is it just a mistaken change in pressure, resulting from the software setting mismatching to the hardware size, that will degenerate the finish?

[yellowshark 153]

Any suggestions on a good model on Youmagine/Thingiverse to use for the test?

[IRobertI 520]

@yellowshark: z-scaring are the bumps or indents you get in the surface at the point where the printer drops the bed down.

Yes, you should set the wall thickness to a multiple of the line width (in the new cura, multiple of nozzle size in old cura).

You will get the line width you set, not your actual physical size (within reason). cura will tell the printer to extrude more or less material to achieve the line width you are asking for.

[ultiarjan 1,223]

cura will tell the printer to extrude more or less material to achieve the line width you are asking for.

and obvious, but sometimes overlooked, not only set the extrusion accordingly, but also the xy movement. Setting a smaller line will result in more lines next to each other = increased print time.

[cloakfiend 995]

When i get home im gonna do some testing of my own too, thin things like fingers at angles are the things ive been having trouble with since installing the ob, everything else seems fine. Bridging is great. Not sure if its to do with the nozzle being different as sander said from the original um one but seeings as i have a spare everything lying around im gonna see for myself. After all beauty is in the eye of the beholder. And in the case of my prints, I am the beholder, regardless of what the settings 'should' be.

[ultiarjan 1,223]

When i get home im gonna do some testing of my own too, thin things like fingers at angles are the things ive been having trouble with since installing the ob, everything else seems fine. Bridging is great. Not sure if its to do with the nozzle being different as sander said from the original um one but seeings as i have a spare everything lying around im gonna see for myself. After all beauty is in the eye of the beholder. And in the case of my prints, I am the beholder, regardless of what the settings 'should' be.

In case you have an specific issue with the default nozzles provided you can also try the E3D nozzles in your tests, as they have a different internal geometry that may be better for your specific type of prints.

[yellowshark 153]

Thanks @lRobertl, of course, it is so long since I had z-scaring I had forgotten what it was! Hmn, well I am still having problems making myself believe that if I have a hole of 0.4mm and I pour stuff through it, I will not get a line that is 0.4mm wide . There is a reservoir of melted filament above the hole which is funnelled down to the hole' I would expect the reservoir to run out of filament whilst giving me a .4mm line rather than give me a .35mm line.

[gr5 2,170]

If you change nozzle size from .4 to .45 but leave shell at .4 or .8 it will do NOTHING DIFFERENT. There's a complicated formula that interelates line size, shell size and nozzle size. As long as shell size is a multiple of nozzle size then the line size will match the nozzle size. Here's the actual formula:

def calculateEdgeWidth():
wallThickness = getProfileSettingFloat('wall_thickness')
nozzleSize = getProfileSettingFloat('nozzle_size')
if getProfileSetting('spiralize') == 'True' or getProfileSetting('simple_mode') == 'True':
return wallThickness
if wallThickness < 0.01:
return nozzleSize
if wallThickness < nozzleSize:
return wallThickness
lineCount = int(wallThickness / (nozzleSize - 0.0001))
if lineCount == 0:
return nozzleSize
lineWidth = wallThickness / lineCount
lineWidthAlt = wallThickness / (lineCount + 1)
if lineWidth > nozzleSize * 1.5:
return lineWidthAlt
return lineWidth

[gr5 2,170]

So for example if nozzle size is .4 and wall (shell) is 1 then lineWidth is .5 (two passes at .5)

If nozzle size is .4 and wall (shell) is .7 then lineWidth is .35 (two passes at .35).

If shell is zero then it is ignored and is always one pass at nozzle width. And so on...

[avogra 68]

In theory, the nozzle size shouldn't matter all that much. The feeder is feeding at a certain rate of volume, the head has a certain gap to the layer below and the head is moving at a certain speed. This is enough to calculate the width of the line layed down, nozzle size isn't a part of the formula. Of course that neglects many side effects and is in general quite naive  but I think it supports that tolerances of the actual size shouldn't have too much effect.

[avogra 68]

oh, @gr5 was 5mins faster and much more thorough.

[IRobertI 520]

Thanks @lRobertl, of course, it is so long since I had z-scaring I had forgotten what it was! Hmn, well I am still having problems making myself believe that if I have a hole  of 0.4mm and I pour stuff through it,  I will not get a line that is 0.4mm wide .

Think ketchup bottle. Turn it upside down, hold it just a couple of mm over your plate, now squeeze it and move it very very slowly. You'll get a big fat line of ketchup. Now repeat the same thing but squeeze less and move the bottle very fast. This time you'll get a skinny line.

[DidierKlein 729]

Thanks @lRobertl, of course, it is so long since I had z-scaring I had forgotten what it was! Hmn, well I am still having problems making myself believe that if I have a hole  of 0.4mm and I pour stuff through it,  I will not get a line that is 0.4mm wide .

Think ketchup bottle. Turn it upside down,  hold it just a couple of mm over your plate, now squeeze it and move it very very slowly. You'll get a big fat line of ketchup. Now repeat the same thing but squeeze less and move the bottle very fast. This time you'll get a skinny line.

Ultimaker 2+ can also print ketchup? I don't get it

[ultiarjan 1,223]

If you change nozzle size from .4 to .45 but leave shell at .4 or .8 it will do NOTHING DIFFERENT.  There's a complicated formula that interelates line size, shell size and nozzle size.  As long as shell size is a multiple of nozzle size then the line size will match the nozzle size.  Here's the actual formula:

 

def calculateEdgeWidth():wallThickness = getProfileSettingFloat('wall_thickness')nozzleSize = getProfileSettingFloat('nozzle_size')if getProfileSetting('spiralize') == 'True' or getProfileSetting('simple_mode') == 'True':return wallThicknessif wallThickness < 0.01:return nozzleSizeif wallThickness < nozzleSize:return wallThicknesslineCount = int(wallThickness / (nozzleSize - 0.0001))if lineCount == 0:return nozzleSizelineWidth = wallThickness / lineCountlineWidthAlt = wallThickness / (lineCount + 1)if lineWidth > nozzleSize * 1.5:return lineWidthAltreturn lineWidth

 

 

I assume this is old Cura? not a programmer but I don't see any get profile settings for the line width? do you know how/if this changed in 2.1?

[gr5 2,170]

Right but the new 2.1 beta might use this formula to create the default line widths? Not sure.

[cloakfiend 995]

Think ketchup bottle. Turn it upside down,  hold it just a couple of mm over your plate, now squeeze it and move it very very slowly. You'll get a big fat line of ketchup. Now repeat the same thing but squeeze less and move the bottle very fast. This time you'll get a skinny line.

 

Lol, whenever i demonstrate 3d printing to people i always use toothpaste, it stacks better. I love ketchup too much to waste it!

Edited March 24, 2016 by Guest

[yellowshark 153]

Lol somewhere in the loft I have a fantastic replica plastic cheeseburger. It used to sit on my desk, holding paperclips inside, and people would walk by, stop and ask if it was real! I will have to use that in my ketchup demo to my next customer

Hi @cloakfiend I think you are wrong because you are changing the speed. This all hangs on the other parameters from nozzle size/wall size staying the same.

For the moment I retain my scepticism; to me increasing the pressure increases the speed of flow, not the dimensions - formula or no formula . And there have to boundaries to all of this, i.e telling the system your .4 nozzle is .1 is nonsensical whereas .39 is reasonable.

Now yesterday I did some more testing. Rather than worry about stringing etc for the moment, vs a flat surface, I focussed on dimensional accuracy, which for me as we produce mainly engineering stuff is the most important factor from our printer.

All settings were the same except for nozzle size and resultant wall size, 2* nozzle. All layers including initial layer were .200. I set nozzle sizes of .34, .37, .4, .43, .46. The result was interesting/strange and needs additional and confirmatory testing.

The .34 setting gave noticeably better dimensional accuracy, for the one piece a square, i.e. not thorough enough at this stage but nonetheless. It hit 10-20 microns, my callipers are rounded to 10 microns. I use the word strange because we guarantee an accuracy of 50 microns (one the x/y axes) but the .4 setting which we have always used was out by over 100 microns.

This result, whilst perhaps questionable in my mind at the moment, has made me a LOT more interested in the subject and motivated me to put more effort into it to try and get proven perspective.

[cloakfiend 995]

I like being wrong, it means i learn things, but im still confused here. I print with all setting the same apart from nozzle size at 0.6 insead of 0.4 with the 0.4 nozzle. All i was saying was that my bridging was improved as such. I printed with the same speed also. The top was not flat and smooth though but that was my reasoning behind thinking the 0.46 size being better than smaller. I am aware that the dimensions will be incorrect from a measuring pov but the quality i felt was great other than extreme plains. I only do this to save time on givaways though. I dont feel 0.46 would save me much time though. And 0.35 would take even longer? I could be completely missing the point though and totally misunderstanding this entire thread? Ive printed many things like this and as the nozzle size is false then so will be the dimensions. a friend has asked me to print something with some accuracy however so it will be my first real micron accuracy test. I doubt i will get it right first time but will try this 0.35 nozzle. My question is that do i need to set the wall size to. 0.7, as i've only used 1.2 for the past year and a half? Have i lost the plot?

[gr5 2,170]

@cloakfiend

Bridging

Bridging likes thicker lines/strands of filament. It tends to break near where you started the bridge because the strand gets too thin and sometimes breaks there. People have requested that Cura somehow (maybe in combination with a special gcode and marlin) over extrudes the first bit of bridge (maybe the first 5mm on a 50mm bridge span? different distances for distant spans?). Just doing thicker layer height or thicker nozzle helps also. Setting nozzle to .46 just for bridging purposes seems - well - like sacrificing one thing for another.

Accuracy

Definition of "line width": Cura's goal for the width of the lines - if your shell is an integral multiple of nozzle then your nozzle width is your line width.

Cura prints inward from the edge of your model by half the line width and spaces the lines by the line width. So line width SHOULD NOT CHANGE ACCURACY. But of course it probably does as @yellowshark claims.

Just to clarify - this is easy to test by slicing a simple cube say 10mm on the side (slice it hollow and with zero top/bottom infill and one shell pass so it's easier to read the gcode). If your nozzle and line width is .4mm you will see that the X and Y lengths of the sides are 10-.4 or 9.6mm! Not 10mm! Cura prints .2mm inwards from the edge on each side. If you change the nozzle/line width to .5mm Cura will accordingly change the lengths of travel for an outer side to 9.5mm (.25mm inward on all 4 sides). Cura does this not just for cubes but for all surfaces.

[cloakfiend 995]

Thanks gr5, so if im getying this right. Then whatever im printing with a 0.35 nozzle entry will be better from an accurate point of view? Regardless of the shell other than being a factor of the nozzle x2? how about x3 as i use that often for strength when printing hollow?

these are with the .4 at .6. Apart from the obvious flat hatched areas and shallow inclines, i really cant see much improvement from .35, as even with .6 its very clean. i cant see how .46 would really make any difference (better or worse) unless it was not a factor of the shell.

Edited March 26, 2016 by Guest

[yellowshark 153]

Lol @cloakfiend, do not worry, I am sure I am as confused as you are! Just trying to get to the bottom of it. Really interesting post by @gr5, which I need to read again to get my brain around before asking any questions/commenting on George.

[gr5 2,170]

Shell can be 3x nozzle size. That's fine. Or any multiple as long as it's an integer (not 2.5X nozzle). But if you ever set shell to a value not an integer of nozzle - well it's just a bad idea. Then you have to go through the code way above in that black code post and figure out what Cura will decide to do. So just don't do it ever. Even for experts. For experts you can lie about your nozzle size but don't mess with "shell/nozzle = integer" rule.

I'm not sure I understand the rest of your post. Physically using a .35mm nozzle should give you more details on your prints. My favorite example is the corner of a cube will (best case) have the radius of curvature of the same as your nozzle. So the smaller the nozzle then the less rounded the corners. and the more other sharp details you can get e.g. wrinkles on someones face.

As for dimensional accuracy - how far apart walls are on a cube - those should only be affected by shrinkage factors. Should. In theory. I don't know what else would affect them. Nozzle width shouldn't affect that. You can use 1mm nozzle and print a 10mm cube and it should be the exact same dimensions (side to side) as if you use a .25mm nozzle. Just the corners will be more rounded.

[cloakfiend 995]

I was talking about a value not the actual 'special edition' .35 nozzles. Lol. I find this topic interesting but will just lay it to rest as i dont think im going to actually bother playing with it too much as im happy with my prints as they are.