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E-steps for different knurled bolt size

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I was looking on the wiki: http://wiki.ultimaker.com/Marlin_Firmware_for_the_Ultimaker%20regarding%20the%20E-Steps%20for%20different%20kind%20of%20extruder%20gears.

Now it says that for Skeingforge below 40 and Netfabb the value is E14 regardless of the knurled bolt used, while for Skeinforge higher than 40 is changing between E926.5 and E865.888 depending on the gear.

I was thinking of making some tests using the old Geo Hangen Extruder and due all the changes in Cura and Marlin I'm not sure what is the E steps value I should set inside Cura's machine settings.

The diameter of the knurled bolt is 20mm (yes, 20), so would it be E5.2 ?

Or I did my math wrong?

Too many things changed both in Cura and Marlin for me to remember and keep up, so I'm asking the Gurus :)


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I presume this is an Ultimaker Original?

With a standard v2 bolt, the 'correct' value is about 830. So if the gearing is still the same, and just the diameter changed, you could calculate the new steps in the ratio of the circumferences of the two knurled bolts. If the new bolt is twice the diameter of the old one, the circumference will also be doubled, so the distance moved by one rotation will be doubled, so halve the steps-per-e.

Once you get in the right ballpark, load up filament and unhook the bowden tube, and use pronterface or similar to feed 100mm of filament in. Measure the distance it actually moves, and fine tune the setting accordingly.


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There is no 'exact value': it depends on the exact configuration of your machine, including the tension on the extruder spring (since that determines how far the teeth press into the filament, and hence the effective diameter of the bolt). 830 is close enough.

If you have an Ulticontroller, the steps value is shown, and configurable in the control->motion menu.

Otherwise, it might be displayed in the status output that gets dumped out when you first connect to the printer with pronterface.

Rather than configuring it in Cura and having it be written out to every file, it would be better to set the steps value with the Ulticontroller, or via gcode, and then save it to the EEPROM.

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You should do a test with print run or some other utility.

Disconnect the bowdentube at extruder drive.

Insert filament flush to top of drive.

Issue command to feed 100mm of filament.

Measure actual filament feed distance and compare to 100.

Alter E constant as a percentage of actual feed.

Example: If feed actual measures 95mm, (5% shortage) change E constant by 1.05X315 or vice versa if feed is too long.

Retest until your actual feed matches 100mm.


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I will, but the popping of the tube wasn't related to that.

I verified it's due a new kind of filament I'm testing which likes to get clogged in the print head (happens also with the normal extruder, but instead it starts grinding)

I am going to try to increase the print temperature from 200 to 210 and see how that works.

I am going to try and verify also the diameter of this new filament, it might be it's 3mm instead of 2.85, hence causing "overextrusion-like" problems.


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