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Calibrate Extruder with restrictive nozzle

rgandhirgandhi
in Questions & Answers
Hello, thank you for producing this software.  I've been using it about a month and it is very respectable.

I'm having trouble printing good prints.  I was given a Prusa i3 (probably Heacent variant).  My filament is 1.75mm, natural PLA.  Using manual feed, extruded PLA is 0.37 to 0.40mm (probably depending on temperature & pull); therefore, I believe my nozzle is 0.4mm.  However, if I try to slice & print with 0.4mm then the quality is poor.   Slicing and printing telling the software I have a 0.3mm or 0.2mm nozzle works much better (hardware is unchanged, 0.4mm nozzle).

I've tried calibrating 'Extruder steps per mm'.  With the nozzle removed (extruder warm), then the default setting of 95 steps per mm (PLA input) is correct within 2%.  With the nozzle in place and hot (200C) then the result is way off.  That is, I might get 65mm of filament pulled-in to the nozzle when commanding 100mm.  In fact, I could boost steps per mm by 200% and the result will still be 65mm pulled in to the extruder.

I've tried changing settings in EEPROM (steps per mm and max mm/s), feedrate, flowrate, speed but can't find a consistent way to calibrate the extruder.  The "best" results lately were feedrate = 100, flowrate = 150 and set the speed much slower in the slicer.

What is the correct way to calibrate extruder to compensate for the restriction of the nozzle?

Thanks!

Comments

  • RepetierSupportRepetierSupport
    The nozzle diameter has no influence for calibration, the amount of the extruded filament is always the same.
  • rgandhirgandhi
    Thanks for the reply.  I appreciate it.  

    There's something I don't understand about the system.  After slicing a model (Slic3R), if I use fast settings and watch the print... I'll see that the extruder can't always push the filament and instead slips (actually, a metal gear chips small pieces out of filament).  In this case, the volume of material extruded is actually different than the slicer thinks it should be.

    Alternately, at a very slow speed, the filament never slips and quality is much better.  Of course this makes my prints take 2x to 3x the time I think it should. 

    In my observations, best quality is when I configure the nozzle to 0.2mm (hardware is really 0.4mm).  I'd think that I should match software configuration to actual hardware configuration rather than fake-out the software in multiple places.

    Is there a way to optimize for speed and quality?  
     - EEPROM
     - Repetier (in ways that affect the slicer)

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