Nylon frustrations...
I've got some parts that will be exposed to high mechanical wear, so nylon seems to be the logical choice. Picked up some red and black. Both nylon 6, Kodak branded. Specifies a 240-270 print temperature. Started with the red and worked through the expected nylon issues. Coating the print bed with a couple of layers of glue stick (still using the one included with the printer) addressed adhesion issues -- almost too well, actually. One of the parts is approx 58mm x 38mm x 1.5mm and it will warp like crazy if there are any adhesion problems. With two good coats of glue, I actually have trouble getting it to release from the bed after printing.
The stuff oozes like crazy, of course. I'm sure moisture is increasing the ooze, but to this point moisture hasn't been a problem with print quality. Surface is smooth and shiny and interlayer adhesion is good. Printer is in an enclosure and the filament is covered in a sealed enclosure on top of it. It isn't completely air tight as the filament path into the printer would still let some amount of air in.
To help keep stringing from impacting the prints, I'm printing multiple parts sequentially. The parts themselves are relatively simple and don't require much in the way of perimeter crossing for the part itself. So I might get a little string connected at the start of the first layer and maybe one coming off the end of the top layer.
All in all, I've printed over three dozen parts without issue (in red). One of the prints was nine copies of a part and took about 24 hours to print. No problems. Note, I'm using a 0.25mm nozzle and 0.15mm layer height, so prints take a while. I'll summarize my print settings in a moment. So then I switch over to black, as I needed to print a bunch of the same parts in black.
Making the assumption (incorrectly) that things would go smoothly, since the red was going swimmingly. Started a print of nine copies of a part, made sure things were printing smoothly and went to bed. Woke up to a blob the next morning. A bit into the second copy, it came unstuck from the build plate and caused a blob to print. This was my fault as I didn't get as good a layer of glue as I should have. I was lucky these were small parts and the blob hadn't really surrounded the hot end, so I could pretty much just pull it off. Had a bit of cleaning to do and put a new silcone sock on and was back to printing.
Now, for the real troubles with the black. Most of the time, the first copy of a part will print fine, but somewhere into the second copy, the extruder gears will start skipping and extrusion stops. It's acting like the nozzle is plugged, but it's not. I can pull the filament, trim the trashed part off, reload it and generally start extruding again without issue. Its almost like the temperature is too low to fully melt the filament, except that it just printed for an hour or more for the first copy of the part just fine.
Print settings:
0.25 mm nozzle
0.15mm layers(0.2mm first layer)
265C nozzle temp
90C bed temp(95C first layer)
20mm/s max print speed
1.25mm retract
30mm/s retract speed
retract 75% before wipe
Those settings work just fine for the red. For the black, not so much. After struggling with the black all day, I decided to go back to the red, to check and see if the blob had cause some problem that was the source of my frustration. Nope, printed six red parts without any real issue. As a second, baseline verification I'm printing a PLA benchy right now. It's about half way through and printing good as ever.
I tried printing a single part in black at 275C and it came out well. Still has a shiny surface and seems to be a good clean print. So I printed a second single part. That one came out ok too. So maybe the temps just need to be a bit higher, I think. Next single part? Didn't even get the first layer going before it stopped extruding.
So I've go no real idea where to go next. I'm sure that using the smaller nozzle is contributing to the problem since its a semi flexible filament and if I couldn't get either to print well, I might just give up. But since the red prints fine, I know it can be done and I'd really like the finer detail of the 0.25mm nozzle.
There isn't much to find on printing nylon in the forums, so I'm hoping someone with a bunch of experience can impart their wisdom.
RE: Nylon frustrations...
Replying to myself rather than editing... since edit times out so quick.
The high amount of retract was put in to help combat the ooze. I might try taking it out since the print path shouldn't actually have much of a problem with no retraction and even with the retraction, it still oozes like crazy anyway.
RE: Nylon frustrations...
Tried a print of three parts this morning. Sequential printing, no retraction. 265C temp.
First one looks great.
Second one, not so much...
The surface of the first one is nice and smooth and it printed no problems. The second one even started to print, as the first few layers look ok.
But then, a few layers in, something happens and the extruder gears start to skip -- game over.
I've got enough filament, for a print of three of the above parts, in the oven drying. I'll try again this evening.
RE: Nylon frustrations...
I had a very similar experience when printing with nylon (PA6/6.6 copolymer with carbon fiber). I took it out of the sealed bag and put on a printer in open air. It printed fine for a few days and then it randomly started clicking and intermittently stopping extruding. The surface was still very much OK, no discernible difference, no popping, no steam. The only other symptom was excessive oozing. I assume the vapor that's produced in the melt zone is pushing the molten filament both ways - out and back up the heatbreak, where it solidifies and causes temporary clogs. After drying at 65 °C (my dryer can't do more) for 24 hours, it was printing great again.
So hopefully your oven will also do the trick.
RE: Nylon frustrations...
I had a very similar experience when printing with nylon (PA6/6.6 copolymer with carbon fiber). I took it out of the sealed bag and put on a printer in open air. It printed fine for a few days and then it randomly started clicking and intermittently stopping extruding. The surface was still very much OK, no discernible difference, no popping, no steam. The only other symptom was excessive oozing. I assume the vapor that's produced in the melt zone is pushing the molten filament both ways - out and back up the heatbreak, where it solidifies and causes temporary clogs. After drying at 65 °C (my dryer can't do more) for 24 hours, it was printing great again.
So hopefully your oven will also do the trick.
I just started a print with filament that spent 8 hours drying at 80C. We shall see how it goes.
I was thinking about it this evening while driving and came to a similar conclusion. My thought is that slow print speed and the 0.25mm nozzle allows any moisture to completely vaporize well before it reached the nozzle tip. The filament reaches 100C well before the melt zone. This steam will generate an internal pressure that would force the filament in every direction. The 0.25mm nozzle creates enough of a restriction that it presses the filament out and back as much as down through the filament. As the filament becomes softer, the pressure will cause it to expand and generate extra resistance against the nozzle walls, acting like oversized filament. Combined with the back pressure, this may be enough to keep the filament from moving smoothly through the nozzle. Since its such a soft filament and the heat of the enclosure, plus the heat from the extruded motor conducted through the gears means that the gears will slip with very little back pressure from the extruder.
That's all just a guess, but if things print ok with dried filament, I'm going to go with that as an answer.
RE: Nylon frustrations...
The answer would appear to be: "dry you nylon filament, even if it doesn't appear to need it". The above picture is the first successful multipart print I've had with this black nylon. As noted elsewhere, single parts that printed showed no signs of moisture impacting the print quality. This was a fresh roll of nylon, straight out of the sealed manufacturers packaging and into an enclosure on top of the printer. Even so, it appears to have needed drying.