Do all metal hotends only work well on direct drive?

Hi all,

I would like to modify one of my printers for high temp printing, I dabbled with a v6 clone years ago and found all metal heatbreaks quite troublesome and prone to clogging.
Most likely low quality kit and heat creep, all the fancy modern hotends look as if they have a very short transition between the hot and cold side.
Does this mean that they only work well with short retractions? (1mm or less) I assume if you retract into the cold side you instantly block the hotend?
And so do all metal hotends really need to be direct drive to be reliable?

plus, does anyone have any experience with the Creality E·Fit Extruder?
[www.creality3dparts.com]

Thanks.

All metal hotends will work fine in a bowden configuration with larger retraction. Quite a while ago, I used to run a 800mm long bowden tube with an all-metal clone volcano. It printed beautifully with only a few quirks that were more related to the bowden than the all-metal. Newer style hotends should work quite well.

Edited 1 time(s). Last edit at 11/17/2022 12:18AM by obelisk79.

Retraction is typically very short for direct drive extruders, usually under 1 mm. Longer retractions will pull hot filament into the throat of the heat break and cause jamming, as you have found out.

You can print with flexible filament with a direct drive extruder, something you can't do with a Bowden extruder. However, direct drive extruders can create a specific type of print defect that isn't usually present in bowden extruders. The defect looks like wood grain in complex shaped prints and like regularly spaced stripes in the walls of things like square sided vases. That defect is caused by the filament drive gears in dual drive gear extruders like the Bondtech BMG and many others. See [www.youtube.com]

Here's an example of the defect from a print made on my printer- it has a Bondtech BMG extruder:

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

Thanks for the replies,

Oh great, that's good to hear.
Wow almost one meter bowden! out of curiosity, can you remember how much retraction you needed for that setup?
What sort of extruder did you use?

Ah, I have seen this video! such a shame an official bondtech product does this.
As the youtuber mentions, I wonder if changing the design to Helical gears could possibly fix the issue.
I assume this affect is only seen on direct drive setups?

Its strange I've been running a dual gear direct drive extruder on one of my printers for many years now and have never seen this effect.
Its a BQ HeatCore DDG, Like this -
[orballoprinting.com]
So it must be down to something specific to the bondtech gear design.

Quote
Plecc
Oh great, that's good to hear.
Wow almost one meter bowden! out of curiosity, can you remember how much retraction you needed for that setup?
What sort of extruder did you use?

I was using a cheap single-gear extruder with blue capricorn tubing and my retraction was 6.5mm if I'm remembering right. I've since switched to my own design based heavily on this direct drive extruder: [github.com]

Shameless sharing, because I'm proud of it. I've nicknamed my take on the extruder as Spritsail and it's extremely light (roughly 100g). Here is what it looks like, along with a recent print using this extruder.


Edited 3 time(s). Last edit at 11/18/2022 01:15PM by obelisk79.

Apologies for the slow response,

Ah, not too outrageous then. I thought it may have been something like 15mm retraction.

Ohhh, very nice design!
Quite a bit cleaner than the Sherpa mini, how do you find the little nema 14 performs. Does it tend to run quite hot?

It runs hot, but not outside of it's expected operating specifications. My assembly isn't in an enclosure so I printed it in PETG, I have no complaints.

Edited 1 time(s). Last edit at 11/28/2022 10:26AM by obelisk79.