Last time we assembled, tested and calibrated the steps per mm of the printer. Now we’ll continue with the calibration steps by pushing some filament through and adjusting the printer profile.

Per Filament Calibration

  • Filament Diameter: Average at least 3 readings from a good caliper and enter that in your slicer’s filament profile. I got 1.75mm as expected.
  • Shrinkage Ratio: Plastics often shrink as they cool. Last time, we measure the physical movement of the print head and adjusted the STEPS PER MM in the firmware configuration file. Now, we’re going to print some test strips and adjust for material shrinkage.

    The math isn’t that hard.
    • If you ask for 200mm and it prints smaller, like 190mm, you will want to increase the size of the print. Simply create a ratio > 1, like ( 200 / 190 ).
    • If it measures long, like 210mm, then you want to shrink the print, so that would be a ratio < 1, like ( 200 / 210 ).

      Then multiply the current setting by your ratio (making it larger or smaller as desired) to get the new setting.

      In Cura 4.3.0 the Shrinkage Ratio seems to have been “locked” in the FLSun QQ-S Profile. I don’t know if that’s a repetier thing, or a delta thing, or what. If dimensions are critical to the print, you can still “Scale” each axis of a model upon “Preparation”.

Note: I had to use that huge scraper they provide to get the first print off the bed. That was scary. I don’t want to do that every time, so I started using the sugar water method shown by Mysimplefix.

Prints stick tight, release when cool, and it cleans up easy.

  • Hotend Temparature: Printing a temperature tower can show what temperature will work best for each filament.

    TechnoGeek 3D shows us how to modify the G-Code in Cura to change temperature at different layers.

What I learned: If you ask for draft quality, you’ll get draft quality. The default setting of 200°C for PLA was good. There was no obvious benefit to changing it.

  • Flow Rate: Now, with the ideal temperature set, we’ll print a cube shell with 2 nozzle widths for wall thickness, 0mm top and bottom, and no infill.

    Measure the wall thickness in the middle of the sides rather than near the corners where filament can build up. For a 0.4mm nozzle, you should get 0.8mm at 100% flow rate in the filament profile.

    Mine measured 0.8mm exactly in at least 3 places, so that looks good.


  • Extruder Gear Tension talks about getting the extruder gear tension correct.
    • After you have your Z Offset set, and you have measured your filament diameter and set it in your slicer, it’s time to focus on that first layer.
    • Print something like my 200x10x0.2mm Test Strip. While it is printing, watch that first layer for gaps, bubbles, ripples or globing.
    • I slowed my print speed down to 20mm/s and adjusted the spring tension on my extruder from end to end while printing. I found a setting around 90% of full tension to produce the smoothest first layer.

That’s all for this time. Stay tuned for updates.

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