What step/mm to use for wormgear ?

[omar23]

Hello everyone, so a week ago i've start building my first ceramic 3d printer i've started by building the ram extruder it uses :
nema 23
R60 microstep driver
30:1 gearbox
1mm pitch screw +nut
duet 2 wifi
?
and my problem is the step/mm or the ram extruder is too high 280000 step/mm
because of the gearbox.
When i use 280000 step/mm the extruder extrude the right amount but i won't change speed
so i've change it to 100 step/mm and i'm thinking change the extrusion factor to 4000%
What do you guys think ?

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[Toinvd]

Are you forgetting that the ram movement of 1 mm will give more mm material because the surface of the RAM is bigger than the surface of the nozzle output.
Nozzle 0.2mm ram 5 mm gives already 625 x more length of material output compared to the ram movement.

[omar23]

yes you're right it dosent need to move that far, but how did you calculate it ?
i have a 5mm nozzle and the piston is 70mm in diameter
thank you

[Toinvd]

Surface of the 5 mm nozle is 2.5 x 2.5 x 3.14 ( Pi ) = 19 mm2 ( roughly )
Surface of the piston is 35 x 35 x 3.14 = 3846 mm2 ( roughly )
So one mm movement of the piston will give 3846 / 19 = 200 mm length output ( roughly again )

[omar23]

ok i see, thank you so much for your help