Don't calibrate, measure! SLIC3R

I did the standard steps per mm calibration for my extruder but was having problems when printing after changing nozzle. Printed interior hole sizes were not correct and surface was not up to snuff. It occurred to me that the Ebay nozzle that I bought may not be the exact size expected. Directly measuring extruded filament is not a great solution do to "die swell."

I used SLIC3R to slice a test cube in the vase mode (print settings, spiral vase check mark) specifying vertical perimeters as 1. After printing I measured the wall thickness and entered the actual thickness in SLIC3R's advanced extrusion width tab. This solved the my immediate problem but if I change filaments (different area) I am probably going to be in trouble as SLIC3R can not automatically adjust.

Any thoughts or suggestions appreciated.

Roger

Changing that number changes the width being extruded. So you should not be able to adjust it to match your actual extrusion unless it already matched at the beginning before changing it. If you want to extrude a single wall thickness and measure it to calibrate you need to change the extrusion multiplier until the extruded width matches the width the slicer is trying to produce which is what slic3r's calibration instructions say to do.

The method of calibrating that Slic3r recommends and is required for Slic3r should not be required if your hardware works correctly and the slicer is doing its job correctly.

My recommendation would be to get a better hotend. Make sure your hobbed bolt is well made, Make sure your idler tension is correct. Use a different slicer (Kisslicer, Cura, Skeinforge or SFact). If you do those things you should never have to calibrate in any way other than setting your steps per mm correctly.

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How would you go about measuring your exact Nozzle size?

Do you just extrude into air and measure the swell?

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ShadowRam
How would you go about measuring your exact Nozzle size?
Do you just extrude into air and measure the swell?

No that would be the die swell size. You need a set of small feller gauges or small drill bits to test the hole size.

To test against your results you measure a single wall print ( cube printed with a single wall, no infill and no top or bottom layers ). Then you change the extrusion multiplier to produce the wall thickness specified in Slic3r. Or at least this is how the Slic3r instructions say to do it.

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The nozzle size entered in slic3r has no effect in whether the extruded width which affects surface fills is correct. Slic3r uses the nozzle size to automatically determine the extruded width. Slic3r calculates the volume required to extrude the correct amount of plastic using the filament width and the extrusion multiplier (fudge factor).

If the nozzle size entered in slic3r is smaller than the actual nozzle size, it ends up stretching the extruded filament too much. This could lead to bridges and sparse infill breaking. If the size entered is larger than the actual size, bridges tend to sag more as too much plastic is extruded. I've found that I can tweak bridges by changing the nozzle size entered in Slic3r using this rule. My j-heads with 0.35 mm nominal nozzle size usually work best with a nozzle size entered as 0.34. In one, I had to lower it to 0.32, perhaps because of crud buildup in the nozzle.

Edited 1 time(s). Last edit at 02/15/2014 11:48PM by brnrd.

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Sublime

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ShadowRam
How would you go about measuring your exact Nozzle size?
Do you just extrude into air and measure the swell?

No that would be the die swell size.

I realize that, but could you not derive the nozzle size from the swell size?

what factors affect swell size?

ambient temperature, extruder temperature, extrusion speed, filament composition, filament density, moisture content, infinity times etc.

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ShadowRam

Quote
Sublime

Quote
ShadowRam
How would you go about measuring your exact Nozzle size?
Do you just extrude into air and measure the swell?

No that would be the die swell size.

I realize that, but could you not derive the nozzle size from the swell size?

what factors affect swell size?

You could make some assumptions and get close but as brnrd said the actual nozzle diameter does not matter that much. It only really matters when you start going down to really low layers and bridging.

The main things that effect die swell from my experience are: Temperature, Extrusion speed, Moisture level in the plastic and of course the plastic being used.

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