0.25 nozzle PLA, extruder skips  

RE:

Posted by: @bob-3

Never have this problem with the 0.4 HF nozzle.  It appears the small nozzle puts strain in the filament causing the extruder gear to wear into the filament until it skips.

Any ideas?

Check if the nozzle is clogged by doing a cold pull. Is there a reason for such a small nozzle vs a 0.4mm?

RE:

Cold pull (twice) looks good.  Some of the detail parts I am printing look much better with 0.25 nozzle (0.25 and 0.4 comparison photo).

RE:

OK. I suspect though it's just the nozzle getting clogged from time to time.

I can't tell how large these are from the photo but if you need fine detail in prints then the way to go (in my opinion) is a resin printer. I picked one up a month ago because I couldn't get the detail I needed from FDM prints. A resin printer typically has 4x the details achievable from a FDM printer. One major downside of resin printers, is that they require handling liquid resin (which is a skin irritant and gets everywhere) and prints have to be post processed. 

RE: 0.25 nozzle PLA, extruder skips

The blue tape in the background is 1" wide, these are small parts.  I figured a resin printer was the way to go for the fine details but I already have a FDM.  😉

RE: 0.25 nozzle PLA, extruder skips

What temperature are you running the nozzle? What layer height are you printing? What is your print speed for perimeters, etc.? Cooler nozzle temperatures and small layer heights can increase back pressure and cause extruder skips especially with high print speeds.  Most PLA can be safely printed up to 230C and a few tenths of a mm difference in layer height will not be likely to have a significant effect on the exemplar models in your picture.  Are you starting with a Prusa .25 nozzle profile or building your own?

From the numbers you cited in your original post you appear to be referring to retraction and de-retraction speeds, those likely have little effect on nozzle clogging, you might want to try reducing retraction length slightly (note this might result in stringing).

Finally, you can increase pressure on the extruder gears by tightening the two screws in the latch on the filament  lever.  Don't add more than a 1/2 turn or so though or you are likely to create new problems with filament feeding.

Regards,

Steve

RE: 0.25 nozzle PLA, extruder skips

I am using the Prusa Nextruder 0.25 nozzle with Prusa Core One slicer settings (only a few modifications).  230 C nozzle temp, 0.12 Structural layers, 70 mm/s perimeters.  The only changes I made to the settings were to reduce the retraction/detraction speeds and slow the entire print speed to 75%.

As you suggest, my next plan is to slightly increase pressure on the extruder.  The filament does not look too bad when I unload it, slight grinding.  I will also try overall speed of 50%.

Thanks for the suggestions,

boB

RE: 0.25 nozzle PLA, extruder skips

Just a sanity check, are you using a high flow nozzle in 0.25 or a normal nozzle? One way to cause extruder gears to slip could be a high flow setting on the printer and profile with a normal nozzle not accepting filament the same speed. I think it is unlikely though since you don’t mention problems with the print itself.

RE: 0.25 nozzle PLA, extruder skips

I need frequent sanity checks.  😉

The 0.25 is a normal nozzle (afaik that is all Prusa has in that size).  Fortunately the printer checks the slicer settings and alerts us if the slicer (0.24, normal) does not match what the printer is set for (my usual 0.4 high flow).

The 0.25 prints look good right up until the filament stops extruding.  One idea is that the frequent retractions are wearing grooves in the filament until it slips.  If so I may try printing a big spiral (no retractions) at intervals to use up 20-30 mm of filament and get it to a new area without grooves before it starts printing the next part.

RE:

I wasnt aware there are no 0.25 mm high flow options but it kind of makes sense in that small diameter. The way I usually mess up is switching the nozzle to a standard and forget the hf setting on the printer, then it still matches between the slicer and printer setting but the nozzle is different.

RE: 0.25 nozzle PLA, extruder skips

One more photo to show what occurred.  It all printed nicely until the extruder stopped extruding, about 15 minutes into the print.  It seems like the filament became either too difficult to extrude/too difficult to retract and then the extruder started grinding into the filament.

I am going to keep working on it.  🙂

RE:

The reason I ended up getting a SLA (resin) printer was precisely this problem. I was printing doll house furniture for my niece and she commented they "don't look nice". At this time (last year) I was using a 0.25mm nozzle on my MK4S with Prusa PLA and beating my head against the wall getting decent results and dealing with constant nozzle clogs. 

I also run into the problem that when I'm not paying attention... I insert the wrong nozzle. When I do, chaos ensues. It would be great if nozzle assemblies could just snap in with RFID tags to automatically set the printer. I think Bambu has this feature... of course... 🙄 

RE: 0.25 nozzle PLA, extruder skips

Update: I have printed many parts with Jessie beige and the 0.4 mm nozzle, no problems.  With the 0.25 mm nozzle this filament just does not work (I tried changing temperature, retractions, speed..., maybe some combination would work but I ran out of patience).  Printing with Prusament Vanilla White and 50% speed works just fine.  Printing at 100% speed still seems to be too much.

RE: 0.25 nozzle PLA, extruder skips

Sorry to hear of your probs.  I did my first nozzle change today (CORE One) and the 0.25 nozzle performed absolutely perfectly, 1 long and 2 shorter prints done. Very pleased with the quality.  I made *no" changes to slicer or printer settings beyond telling the printer I'd changed nozzle size.  The prints were deliberately done with very thin layers to see the most benefit. 

RE: 0.25 nozzle PLA, extruder skips

have you checked thermal compound for improving contact in the "cold" area of the nozzle? I found this only yesterday, and it seems a logical improvement. 

I know from electronics that thermal resistance without thermal compound is usually hit-and-miss because air is a fairly good insulator across a largely uncontrolled gap.

RE:

Please have a look at my settings to create the "perfect" carbon sheet 1st layer.
I had a lot of issues, very similar to yours.
It's a combination of trying too high flow, not enough temperature, heat creep due to too low flow etc.

My solution: print very slowly, set the target heatbreak temperature down from 36°C to 32°C and: open the door a little bit or raise the chamber fans A LOT.

The filament in the extruder becomes a tiny bit too soft to push it through the tiny nozzle.
So you need to reduce the flow, but also keep the filament from becoming too warm inside the extruder, which is caused by the heatbreak fan running too slow, intake air not being cool enough or the filament staying too long in the heatbreak (but you can't increase flow with the 0.25 nozzle).

You can download my 3mf at the bottom of the thread and also: have a read on how to enable the heatbreak temperature reading for the display.

https://forum.prusa3d.com/forum/prusa-core-one-how-do-i-print-this-printing-help/my-perfect-carbon-look-build-plate-settings/

RE: 0.25 nozzle PLA, extruder skips

I believe you are on the right track.  I tried a slower speed and left the door open, that worked for some prints.  Lowering the heatbreak temperature seems like a good idea.

I will reprint some of the failed ones and see if this works, thanks!