Nylon filament arrived Friday afternoon. Have been running test prints, off and on, all weekend.
I was surprised at how soft and flexible the filament is. It's obviously nothing near as flexible as TPU, but it's more like TPU than PLA or PETG in flexibility. I've had three "jams" this weekend. None of them were a blocked nozzle, but anything that makes extrusion a bit hard (like trying to extrude too cold) will almost certainly jam up the filament at the extruder gears. In one case, the gears just ate enough filament away that they couldn't get a grip. In another, it started to spit filament out the side of the extruder gear opening, like can happen with TPU. In all the cases, releasing the extruder gear spring tension and pulling the filament out (with the nozzle heated) was all the was needed.
The big take away from the weekend of printing -- glue stick for teh win!
The Prusa Mk3 has a PEI coated build plate. Nylon doesn't stick to it. Period. However, simple glue stick coat solves that problem very effectively. In fact, almost too effectively. Elmers white glue is contains PVA while sticks to the PEI. The white glue sticks use a cellulose filler and the nylon sticks very well to that. So well that if I let things cool, it will separate the PEI from the steal plate, if I'm not careful.
Moisture. Go read up on nylon and everyone talks about how hygroscopic it is, and drying, and storage. It rained all last week, and Friday and part of Saturday were overcast and definitely humid. I haven't had humidity related issues, with one exception -- oozing. For now, I'm chalking it up to printing with a 0.25mm nozzle and a fairly slow print speed. The result is that the filament feed rate is quite slow. This means that it spends a fair amount of time (relatively) above 100C. So I'm thinking that the extruder is effectively pre-drying the filament. The purge line printed right at the start of the print has a very high extrusion rate relative to normal printing, and it does show signs of moisture in the filament. I'm not seeing any surface or other print defects one would expect from moisture in the filament, especially a filament that has effectively been sitting in reasonably high humidity for three days.
Oozing... Nylon oozes like crazy. Damp nylon oozes even worse. This is the one place that I have noticed the moisture.
The "mohawk" on that part it due to ooze happening as the print head moves from another part, across the build plate, to start the next layer on this. The print was of nine identical parts and this was the first in the layer cycle. The individual hairs line right up with the layer start/end points. Another example:
Again, all the hairs line up with start/end points and the rest of the part surface is in pretty good shape. The photos above are the two worst parts. From the print of the cylindrical part, that was the only one that was not good enough to keep, once the hair was trimmed off with an exacto knife. I'm actually re-running a print of the ball shaped parts printing them sequentially, instead of in parallel, to see how that impacts the print quality.
I do plan to dry the roll of red nylon I've be running test prints with, and I'm also picking up a cover that I can place over the filament spools on the printer to greatly reduce the moister absorption.
I'm printing with Nylon 6, and it warps if you look at it crossways.
Enclosed printer is a must. I'm using a 90C first layer and 95C subsequent layer setting for the build plate. Even so, I had one of the ball pieces warp badly. The other eight were fine. Trying to print larger flat surfaces requires you to pay special attention to adhesion, or you'll have a corner pull up, especially if you build plate temperature is a bit on the low side and/or particularly uneven across the surface.
I'm using Kodak nylon 6 filament, which is listed at having 240-270C print temperatures. I have found the higher end of that range to work best for me. I've settled on 260C as working well. I imaging the higher temperature helps contribute to the oozing problem, on top of moisture, but the layer adhesion, bed adhesion, and surface finish are much better and printing sequentially, rather than in parallel stops the oozing from being a factor.
My replicated parts on the left. Originals on the right. The stop spacer (tall cylinder), I don't have an original for.