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dwardio

Cura settings for Olsson block w/ 0.8mm nozzle?

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Received my Olsson block upgrade kit and got it installed last week, but ran into an odd situation: I decided to test printing with the included 0.8mm nozzle by (re)printing the Nozzle Torque Wrench ( https://www.youmagine.com/designs/nozzle-torque-wrench ).

I made sure that the nozzle size was set to 0.8mm in Cura and that infill was set to 100% as per the instructions. Print preview looked fine, but the "vanes" or "fingers" on the internal piece did not print.

It this a case where the x/y thickness was just too small to be printed at .8 mm, or have I perhaps missed something else?

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I think you got it in one. The "shell width" is more important than nozzle width so leave nozzle width at .8 and try shell width at .7, .6, .5, .4 and look at layer view and see where the vanes come back in. You can print with a .4mm nozzle down to about .3mm shell and you can print a .8mm nozzle down to about .6mm shell. But of course the quality will be reduced a little. It may appear to be a bit underextruded. Of course you can then bump up the flow but now you may have bad tolerances when you try to put the torque wrench tool together.

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Ok — mind officially blown — it never occurred to me to set shell thickness to a value less that the nozzle. 99% of my prints require two shells for strength, and since Cura doesn't seem to have a separate "number of shells" setting, I've always set shell thickness to 2x the nozzle diameter.

Re-ran the layers view in Cura and it would appear that .7 is the max shell width that will work, but will run a couple of tests this evening.

Thanks again for your help! I printed out 4 Raptor Reloaded hands ( http://www.thingiverse.com/thing:1033475 ) over the long weekend using the 0.6 nozzle and it saved me at least 2 hours per print at 130% scale. If I can get the .8 nozzle to print some of the "fiddly bits" such as the finger pins, I should be able to really cut down production time...

I think you got it in one.  The "shell width" is more important than nozzle width so leave nozzle width at .8 and try shell width at .7, .6, .5, .4 and look at layer view and see where the vanes come back in.  You can print with a .4mm nozzle down to about .3mm shell and you can print a .8mm nozzle down to about .6mm shell.  But of course the quality will be reduced a little.  It may appear to be a bit underextruded.  Of course you can then bump up the flow but now you may have bad tolerances when you try to put the torque wrench tool together.

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If you have a .6mm nozzle then that would be better than the .8mm nozzle for this tool.

Anyway it will probably come out okay - not sure. The tolerances are important to get the right torque - or reasonably close.

In general there is a formula in Cura that determines "line width". The line width for an entire print is always the same which is weird because I would think the infill should match the nozzle width. But it doesn't. The line width is how thick the line is (the goal thickness) when it lays down a line. The line width determines 3 things: the spacing of lines, the amount to extrude, how far in from the edge to print (half line width) such that the part is dimensionally correct.

 

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

 

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I can never remember the above formula but the general rule is, if the shell is very close (within 20%) of a multiple of the nozzle width, then it takes the shell width and divides by that multiple to get the line width.

So for example if nozzle is .4mm and shell is .7mm then it will do two .35mm lines.

If nozzle is .4 and shell is .8mm then of course, two .4mm lines.

If nozzle is .4 and shell is .42mm then one .42mm line.

If shell is thinner than nozzle it pretty much always uses shell - exceptions above for example if < .01mm. Best to go through above code for a specific example. It's pretty simple to run through the above code with a specific nozzle and shell size (shell is called wallThickness).

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