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Problems getting started with 0.25mm nozzle  

Active Member
Problems getting started with 0.25mm nozzle

First, let me say that I have changed nozzles many times - but only going UP in size from the standard 0.4mm nozzle. I've used 0.6mm and 0.8mm nozzles with good success for a few years now. I only mention that as I have competently changed nozzles maybe two dozen times (between the aforementioned 0.4, 0.6 and 0.8 sizes) and I use an (automotive) feeler gauge to get a pretty near-perfect (for me anyhow) half-millimeter gap between the nozzle and heater block.

But now I am trying to use a smaller 0.25mm nozzle and I'm having early problems. When I say early problems, I mean even before trying to print any models or worry about slicer settings or profiles or anything. Literally, I am having problems just trying to load the filament and get it to extrude properly in the printer itself. If anyone has any suggestions for special steps I need to take (again, pre-slicer) for a smaller nozzle, kindly let me know. Here's the process I followed (which is what I do when I change back and forth between 0.4mm and larger nozzles):

1. Heat up the filament (PLA) and then let it cool down and do a good cool pull before changing nozzles

2. Heat up whatever previous (brass) nozzle was in there to around 230 degrees and remove it. 

3. Installed the brand new (E3D OEM) 0.25 nozzle leaving only a small (0.5mm) gap to the heater block

4. Change the MK3 printer settings to tell the printer there is now a 0.25 nozzle on it

5. Load the PLA (keeping it at the 230 degree temp to give it a little extra initial melt)

Expected result: PLA extrudes properly and I can move on to a first layer calibration (which I usually do after changing nozzles)

Actual result: PLA barely extrudes at all. Maybe 7mm. Then the hot end makes the clicking sound like the extruder gears are struggling to get hold of the filament. Played with slightly losing and tightening the screw as well as opening up the door and confirming that the Bondtech gears are aligned (they are). I don't have this non-extrusion, filament loading problem with the 0.4mm or larger nozzles - just this new 0.25 nozzle.

Other Info

I've done several subsequent cold pulls and there doesn't seem to be a clog. I've also used the end of an acupuncture needle in case there was a tip clog. There is no leaked filament around the heat break or heater block. The filament doesn't seem to be getting down to the heater block - or at least not much of it, even if I answer "no" when the printer asks if the filament is extruding and the right color. Just lots of clicking from the extruder.

Since this is all pre-slicer, I am not sure what to do. I assumed that when I set the printer settings to tell it I had a 0.25 nozzle installed that the firmware would automatically adjust the flow rate and speed to something that the smaller nozzle would tolerate. But the way it is behaving as if that hasn't happened.

Any ideas?

Thanks in advance!


Posted : 29/03/2022 1:51 am
Eminent Member

I've had similar issues using a 0.25mm nozzle.  I can typically get maybe 15 minutes of printing out of it before it clogs and the extruder starts skipping.  I've never really figured out the solution, unfortunately.  To be fair though, I've not really delved deeply into the troubleshooting, as I can usually accomplish what I want with a 0.4.  And if I can't, I use my resin printer.  🙁

The best suggestion I can make for now is to suggest that you jack the temperature of the nozzle up near the top end of the filament's rating.  Hotter material should flow easier (in theory).  Careful though, as overheating can actually harden the plastic.

Another suggestion is to perhaps increase your extrusion to 100%.  I won't admit to fully understanding that part, but to my mind, increasing flow rate would increase the pressure within the nozzle.  By increasing the temp and making the material more fluid, as well as increasing pressure, I'd imagine that would ensure a steady flow of material and wouldn't give it time to back up in the nozzle.

Please realize that these are theoretical suggestions with absolutely no basis in practical testing.

This post was modified 2 years ago by Dave
Posted : 29/03/2022 2:16 pm
Illustrious Member
RE: Problems getting started with 0.25mm nozzle

That sure sounds like a partial clog. I've had this happen with cheap nozzles with poor internal finish, but not with better quality like E3D or P3-d. Can you try another 0.25mm nozzle?

You could try adding 10C temp to make the filament more fluid. Hopefully it's a conditioning thing that will clear up with use.

Coated nozzles might help.

On my non-Prusa printer with overall poorly finished parts, I did have to "season" the hotend with a bit of vegetable oil (1-2 drops) to get things moving. Definitely cover your bed if you try this, as any oil will really screw up PEI adhesion.

Other than that, 0.25mm are easy enough to work with. There will be more back pressure, so higher temps or slower speeds may help.

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Posted : 29/03/2022 2:45 pm
Prominent Member

Going downwards in nozzle diameter is a bit trickier than going up. At 0.25 mm clogging can become an issue with filaments which have absolutely no clogging issues at 0.4 mm. There are substantial differences between filament brands even of the same material type. 

  • Finding out which brands have a nice and easy flow and low tendency to clog even under more difficult circumstances is key. Have a try at a few different PLA brands with your 0.25 mm nozzle, maybe not the cheapest ones (doesn't mean expensive ones can't clog though).
  • Increasing hot end temperature to higher values than those you'd use for 0.4 mm can help, but one has to balance that with print quality. In case it's needed, compensate the higher temperature with slower printing speed. Can't hurt anyway as you'd probably want to have fine high quality prints which aren't too huge with a 0.25 mm nozzle. 
  • If problems persist, have a look at retraction. In the worst case reduce or even turn off retraction. Doesn't make the print look nicer but can help against clogging. 

As crazy as it may seem. I had the experience that if you are using an 0.25 nozzle together with an MMU that the MMU can actually unclog the nozzle during color change. Not that this is a practicable thing in most situations it is maybe of help for the one odd situation. 

This post was modified 2 years ago 3 times by Thejiral

Mk3s MMU2s, Voron 0.1, Voron 2.4

Posted : 29/03/2022 2:49 pm
Active Member
Topic starter answered:
RE: Problems getting started with 0.25mm nozzle

Realized I never tied off on this thread.

Even though I used a quality E3D nozzle - SOMEHOW it just wouldn't extrude from the get-go. As I mentioned, I couldn't even get to a test print - it was already FUBAR as if there was a clog from the factory. Sounds unlikely, I know, but that's how it behaved.

Maybe it was defective. Anyway, I spend way too long trying to clean it and clear "the clog" to get it to work, but to no avail.

Ultimately, I ordered and received a second 0.25 nozzle (also from E3D) and had no issues after that.


Posted : 18/07/2022 12:23 am
Eminent Member
RE: Problems getting started with 0.25mm nozzle

I print on .25mm on multiple printers for days on end with no issues. Use PETG, + increase temps a bit. 

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Posted : 19/07/2022 4:55 am