How to calibrate the extruder

Brmatt

I have found that my extruder is WAY over extruding. It pushed out a little over 14 inches of filament when instructed to push out 50mm. Seems its over extruding about 7 times too much. I believe this is the parameter I need to change however I am unsure about the formatting of it. Is it a set up as E(steps):(mm)?

Stephen6309

@brmatt The extruder is calibrated for the amount of filament going into the hotend.

Brmatt

And? Sorry I don't follow what you are saying

Brmatt

For reference I am using a bowden tube set up and while testing this I was not feeding into the hotend, just out if the end of the open tube. I told it to extrude 50mm at 5mm/sec. Instead it extruded around 350mm.

aidar

Have you ever read documentation? specially section https://duet3d.dozuki.com/Wiki/Step_by_step_guide#Section_Initial_configuration

Stephen6309

@brmatt You calibrate for how much filament fed into the extruder, you don't use what's coming out of the nozzle.

Phaedrux

@stephen6309 I dont think he has the nozzle on, so as long as you're measuring from the right points it's a totally valid way to measure e steps.

Phaedrux

@brmatt M92 E###:### refers to two seperate extruders. If you only have one extruder, you can remove the colon and second value.

The number itself refers to the steps needed for the motor to move 1 mm.

I just noticed that the guide in the Duet documentation is not yet written (I should fix that) but here's another guide that gives a good overview on the general procedure.

https://mattshub.com/2017/04/19/extruder-calibration/

It's specific to Marlin, but the math is the same.

You can use this formula if you have a known gear ratio extruder to get you close to the ideal steps per mm.
e_steps_per_mm = (motor_steps_per_rev * driver_microstep) * (big_gear_teeth / small_gear_teeth) / (hob_effective_diameter * pi)

Then you can use the actual extrusion measurement to fine tune it with this formula.

New e steps = old_e_steps * (100 / (110 - distance_to_mark))
M83; to set relative extrusion
Make a mark on filament 110mm from the top of extruder
G1 E100 F100; extrude 100mm at slow speed
Measure distance from top of extruder to mark.
If it went below, estimate how many mm it went down, and enter a negative number.

The longer you extrude, the more accurate your final result would be. 100mm is a good start. You may need to repeat the process a few times.

dc42

If an E steps/mm of 663 is about 7 times too much, then I guess you are using an un-geared extruder. Is that correct? Those usually have around 100 steps/mm.

Brmatt

@stephen6309 as Phaedrux said I don't have the nozzle on that's what I meant when I said "not feeding into the hotend, just out if the end of the open tube"

Brmatt

@dc42 That is correct it is un-geared. Thanks for the advice. Ill start messing around with the number.