I'm looking for a cheap geared dual drive 3mm/2.85mm extruder



  • Alot of different designs for 1.75mm on aliexpress, but nothing with 3mm. I can't invest in an original bondtech right now.

    Closest thing I could find was this, but I prefer a version with geared extruder, not a geared motor. https://de.aliexpress.com/item/32956895566.html?spm=a2g0s.8937460.0.0.6b492e0e5t6HWK



  • 3mm filament is becoming less and less popular.
    all the new hotends are 1.75 only. (mosquito,hermea, etc.)

    the bondtech one is the only 3mm i know of.

    maybe consider switching?



  • @Veti Even if its offtopic. Is there some info why 1.75mm was chosen?



  • @PCR

    3mm has the following issues:

    • requires extreme force to be pushed through, especially in bowden setups, thus requiring geared extruders.

    • it is FAR stiffer than 1.75 which in combination to brittleness of some materials (PLA) makes it really REALLY easy to break. and i mean really, up to the point it is barely usable.

    • it takes longer in the melt zone to melt, thus limiting printing speed

    • it requires a bigger melt zone, increasing oozing by several order of magnitudes compared to 1.75

    • due to the reasons above, you have to have way slower retractions than 1.75, which means more oozing, more risks of clogging etc.



  • @Veti I know the benefits of it 😉 Only want to know where the number 1.75 came from? 😉



  • propably has to do with the availability of 2mm ID and 3mm ID pneumatic tube back in the day when there were no 3D printing specific products, at least this would be my guess.

    ...aside from the bondtech QR there's also the bondtech DDG that is an upgrade for the Ultimaker but should be able to be used separately?


  • Moderator

    @rhklein See my post: https://forum.duet3d.com/post/168110
    I'm still working on it, just haven't had much time! I've pretty much done the Wade/Bondtech gears mashup, but still haven't got around to printing it and testing it out. A 3mm BMG-style from DDG parts is some way off.

    Ian



  • @Veti said in I'm looking for a cheap geared dual drive 3mm/2.85mm extruder:

    @PCR

    3mm has the following issues:

    • requires extreme force to be pushed through, especially in bowden setups, thus requiring geared extruders.

    • it is FAR stiffer than 1.75 which in combination to brittleness of some materials (PLA) makes it really REALLY easy to break. and i mean really, up to the point it is barely usable.

    • it takes longer in the melt zone to melt, thus limiting printing speed

    • it requires a bigger melt zone, increasing oozing by several order of magnitudes compared to 1.75

    • due to the reasons above, you have to have way slower retractions than 1.75, which means more oozing, more risks of clogging etc.

    Those are all valid points if one uses "conventional" size nozzles. We could also add that 3mm diameter filament has a cross sectional area that is almost 3 times that of 1.75mm diameter filament so if one wanted to maintain the same resolution, the one would need to use roughly 3 times the steps per mm for the extruder - say 9:1 gearing instead of 3:1.

    Of course, we don't know what the OP's usage case is. If he wanted to use a nozzle diameter greater than (say) 1.75 mm, then 3mm diameter filament might be the better choice (providing he can melt it a sufficiently high rate and also cool the resultant volume of extruded material at a fast enough rate to prevent the part from sagging).



  • I can confirm that a 2mm nozzle on a 2.85mm system is fun (Bonddtech DDG on UMO+ with UM2 extrusion kit here). At the resolution of larger nozzles (1mm+) no extra gearing is is needed.

    It's worth noting that the DDGs esteps are much lower than the original Ultimaker extruder, with no noticeable differences in extrusion quality to be detected by my Mk1 Eyeball (and maybe the dual gear setup compensates a bit).



  • Interesting points about 1.75mm vs 3mm.

    Originally plan was to use 3mm for some experimental printing, because it seems cheaper nowadays.
    But building my own extruder isn't worth it, been there with a 1:5 belted extruder for my diamond hotend, but the bondtech extruder work more reliable.


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