Easy E-Steps & Rotation Distance Measurement Tool + Instructions

Please don't forget to like - I want my Prusameters! 😄
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I love good tools, but got a little bit mad with using my nice caliper for calibrating e-steps / rotation distance, because I got inconsistent results on re-measuring.

This tool has for this task quite some advantages over a caliper, as it is much easier to hold & handle, forces always the correct base measurement point on the extruder, allows to set the marking points repeatedly precise, and provides much easier reading.

In more details:

• Channel for the filament. This forces the filament to where it belongs. There are also no measurement errors due to bending.
• Easy and precise marking thanks to an “entry point” for the marking pen. In contrast to the caliper, the marking pen can be placed exactly at right angles.
• Instead of a wide, unclear line, whose position with the caliper depends on the angle of the pen, you can set an exact point where it is always clear that its center is exactly the measuring point.
  It is designed to work with any CD-markers - no special thin marker neccesary.
• It is not possible to mis-measure on extruders which have a small raised inlet for the filament.
• Easy to read, thanks to the brightness of the tool, the cutouts that provide contrast, and the fact that the channel inevitably keeps the filament straight and close to the scale. I've experimented with different styles of the scala. This one seems to be the best-readable what's possible to print with a 3D printer.

How to print it?

• Slow. If it takes 2 hours that's fine.
• Ideally white, or maybe another bright color (haven't tried). Otherwise the scala's bright-dark-contrast for the (sub)millimeters doesn't work.
• Without supports.

How to use & calibrate?

I think the tool itself is so enforcing that it's hardly possible to use it wrong - almost. At marking, don't try to draw a line, just set a point:

There are insertion openings for the marker pen. Place the pen sideways and straight, then tilt it (straight) toward the center until the tip of the pen marks the filament.

If you prefer, you may also cut the filament at 100/110/120mm.

To calibrate E-Steps or Rotation_Distance:

• If you use the Klipper Printer Additions you can just click the button “Calib Rotation Distance”, and it will do the 100mm-extrusion and the calculation for you.
• In Mainsail / fluidd, set the Filament Length to 100mm.
• Set the Extrusion Feedrate to 1 mm/s (you don't want extrude fast!).
• Use the tool to mark the filament at 120mm distance.
• Extrude.
• Use the tool to measure the marked point. By the bright/dark-contrast you can even see down to 0.5 mm. :-) The middle of the white bars are the uneven millimeters (1/3/5/7/9) while the middle of the dark slots are the even numbers (2/4/6/8).

If the mark is below the 20mm mark, it's extruding too much. Let's say it's at the 16.5mm mark, so that's 3.5mm to much extruded, or equally 3.5% of the desired 100mm.

Simple calculation:

103.5 / 100 * <Your current value of rotation_distance>

Let's say your current value for the rotation_distance is 4.555:

103.5 / 100 * 4.555 = 4.714 is your new value.

It may be a bit counter-intuitive as the value needs to be RAISED if the extrusion is TOO MUCH, and vice versa. But as it is a rotation-*distance*, it actually makes sense.
(For adjusting E-Steps, it's just the other way around.)

So if the extruder would have extruded 3.5mm (Percent) LESS than desired, the rotation-value needs to become LESS too:

96.5/100*4.555 = 4.396 (rounded to the 3rd digit)

• You find the “rotation_distance” inside of your “printer.cfg” file.
• I advice to extrude 100mm, as this raises accuracy (some advice to extrude only 50mm), and it makes the math easier.
• It's good enoug calibrated if you are below 0.5mm deviation.

Feedback welcome. If you print it in other bright colors, please post a Make. Or maybe you use this even for something completely different? :)

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Christian 🙂