Back-pressure problems with a 0.25 nozzle
I changed my 0.4 nozzle to a Steel E3D 0.25 nozzle and have a big problem since then.
I think it's a back pressure problem, since the first centimeter of the print goes ok, then i can hear the extruder skipping for a good long while.
Then after one or two layers of the material are missing, it goes back to extruding again. (after it has space to flow out again it seems)
I've tried prusa's stock settings, and my settings that i print since a good year now with (changed to the 0.25 nozzle in printer and print settings). Nothing works.
My extruder is a E3D Titan (with the 3:1 gear ratio), and a good 900mA are applied to it, compared to Prusa's stock 600mA on the stock stepper.
Also a weird thing is, I print in an enclosure, with the door closed (chamber heats up) the back pressure problem comes much sooner; with the door open, the back pressure problem comes much later.
I can rule out a software problem from Slic3r, but that makes me wonder, what is going on... 😐
Tried:
- using all sorts of settings in Slic3r
- cooling down the stepper motor with a fan
- disabling retraction and Z-hop
- trying different first Z layer heights
- repeatedly dis-/assembling the Extruder completely
I spent a good week now with this problem, and i can't even print Benchys correctly (there are always some layers missing, mostly around 1cm in height)
Halp!
Re: Back-pressure problems with a 0.25 nozzle
A few things I would try:
Reducing the filament feed tension
Reducing motor power by at least half
Increasing temp by maybe 15 degrees
Doing a few cold pulls.
Reverting to a 0.4mm nozzle just to check.
Junking the steel nozzle; there's no point most abrasive filaments won't go through it anyway - switch to plated copper.
Peter
Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…
Re: Back-pressure problems with a 0.25 nozzle
A few things I would try:
Reducing the filament feed tension
Reducing motor power by at least half
Increasing temp by maybe 15 degrees
Doing a few cold pulls.
Reverting to a 0.4mm nozzle just to check.
Junking the steel nozzle; there's no point most abrasive filaments won't go through it anyway - switch to plated copper.
Peter
Reducing the filament feed tension - already at the lowest setting, also tried the middle
Reducing motor power by at least half - i kept increasing the current, up from 800 that the titan regularly needs to 950mAh now
Increasing temp by maybe 15 degrees - tried that too
Doing a few cold pulls - today i did about 20 of them throughout the day
Reverting to a 0.4mm nozzle just to check - will try this next. everything worked wonderfully up to the point in switching to the 0.25 steel nozzle.
I have the same printer setup at work (i3 MK2 + Titan + 0.25 nozzle) and got the same problem there too.
Will copper nozzles perform better than the steel ones?
Re: Back-pressure problems with a 0.25 nozzle
Swapped to a 0.4 nozzle now, no problems whatsoever.
Strange. i can't get the 0.25 nozzle to work right on two printers now. even with 3 times the pressure of the e3d titans
Re: Back-pressure problems with a 0.25 nozzle
...
Peter, just a thought.
If i set the extrusion multiplier down by a few percent (like 95%), it could get rid of the back pressure.
What do you think?
Re: Back-pressure problems with a 0.25 nozzle
No changing the extrusion multiplier will only reduce the volume of filament being fed.
I presume that your extrusion width is set correctly? (between 0.25 and 0.3mm)
Copper has much better thermal properties than steel (and brass) so plated copper nozzles should be able to work better. Yes, they will wear out quicker (I change mine every 2 months or so) but unless you are printing with abrasive filaments (which you can't be) you can print at lower temps and for me, they do work better.
A 3:1 reduction will reduce speed and increase torque (by a factor of 3 assuming no losses) so you should only be using one-third of the power. The standard motor gives enough "push" to melt 10 mm^3/s of most filaments (with temps at higher end of that recommended for the filament).
Using a 0.25mm nozzle, layer height should be around 0.1mm (maximum 0.2mm) and width of around 0.26mm (max 0.3mm). So in theory, you could print up to almost 400mm/s, but the printer can't handle that (100mm/s is about the maximum), so you are well within limits and you really don't need to heat up the motor.
Peter
Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…
Re: Back-pressure problems with a 0.25 nozzle
A 3:1 reduction will reduce speed and increase torque (by a factor of 3 assuming no losses) so you should only be using one-third of the power. The standard motor gives enough "push" to melt 10 mm^3/s of most filaments (with temps at higher end of that recommended for the filament).
Using a 0.25mm nozzle, layer height should be around 0.1mm (maximum 0.2mm) and width of around 0.26mm (max 0.3mm). So in theory, you could print up to almost 400mm/s, but the printer can't handle that (100mm/s is about the maximum), so you are well within limits and you really don't need to heat up the motor.
Peter
The Titan won't budge at all and only skip with a current of under 650 mAh. (Motor is a Wantai 0.9 degree 1.2Ah stepper)
I think the back pressure problem is also temperature related. Like i mentioned in the first post, when i close the door to the case, a blockage of some sort is forming up.
With the 0.25 nozzle, it started after about 1cm in height.
Yesterday evening, i put in a 0.4 nozzle and hit print, today morning the print stopped at around 10 cm in height.
This was with the door closed. Temp inside the case is around 42 degrees.
With the door open the same print is still going now reaching 16cm and going.
I don't get this problem.
The exceptionally good e3d Hobbgoblin gear eats itself into the filament because of this, but only if the room temp is 10 degrees warmer than usual.
This also only occurs with PLA, printing ABS and PETG are fine.
Re: Back-pressure problems with a 0.25 nozzle
Maybe your PLA is softening way too early. You should vent the enclosure for PLA prints.
Re: Back-pressure problems with a 0.25 nozzle
Maybe your PLA is softening way too early. You should vent the enclosure for PLA prints.
Could be part of the problem.
I noticed a couple of times when i yanked out the filament via a cold pull that it had a weird squished shape where the hobbed gear is. Not just eaten away at the filament, but slightly melted.
i strapped on a fan onto the Extruder motor so that the heat from it goes away (which was transmitted to the hobbed gear), and it seems better now.
Still not fully gone though.
Pondering a place where i could put a fan setup that also absorbs noise. Perhaps a HEPA filter block with a fan behind it.