Printing with El Cheapo Nylon

(All photos are thumbnails, click to biggiesize)

So after doing some extensive googling and poking Greg with a few questions, I decided to give printing Nylon a try with the theory that it might stand up well to damage. So I did two things, first, I ordered some expensive as heck Taulman's Nylon to print with, and then I ordered this:
Amazon.com : Maxpower 333665 Residential Grade Round .065-Inch Trimmer Line 1800-Foot Length : String Trimmer Lines : Patio, Lawn & Garden

According to what I was able to dig up, this is made from virgin Nylon-6, with no filler fiberglass fibers to strengthen or anything else funky, and then dyed blue, coiled up into 3lb spools, and shipped to you for your weed whacking enjoyment. Or for some silly folk, 3lbs of cheap Nylon filament for 22$.. if it works... Its cheap though and I'd rather mess up on cheap nylon than the Taulman's.

First thing I did was throw it in the oven overnight at about 'Warm' to drive out some of the moisture content of the reel. In doing so I discovered that one should allow for the expansion of the reel and had a fun time getting the reel and the upper oven element separated the next morning. I then bagged the reel up with some extra desiccant, took it to work and forgot about it in my desk drawer for a few weeks.

On to the testing. After some digging I found that it was suggested to run Nylon6 prints around 240-250C on a bed heated to 60-80C with a wide variety of bed surfaces suggested. Nylon doesn't tend to stick to much but it does like organic surfaces. Wood, fiberboard, cardboard, paper, cotton fabric were all suggested. I opted to give ye old glue stick a try and liberally slathered it on my printer's bed as it warmed up.

First I though, I'll print some boats, so I dropped two of @rcengr's whalers into cura and sent the job to the printer. Out came two little whalers, nice as can be other than Lesson 1: Nylon can get really stringy when moving between parts. I had 5mm retracts but I guess it wasn't enough.

Once the bed cooled down enough I pried them off, they stuck really well, I think I could have printed them easily without brim. Washed the glue stick residue off with a quick swirl in a mug of isopropyl alcohol.

With that coming out so well, I sent the files for the Potemkin turret base. I quickly discovered my extruder simply couldn't feed the nylon filament very fast or with a great deal of force and had to slow the prints down, and even then I still had problems with it slipping and the hotend going hungry a little as I tried to hand push the filament a little. I am still unsure as to whether I could help this by running hotter or cooler at this time After excessive amounts of annoyance, I got a series of turret bases printed, only 1 without significant losses from filament starvation though.



I wanted to test thin walled nylon structures to see if they would be able to deflect under impact and observe their failure mode if they did fail, and how well the surface itself would hold up. So I printed 3 turret bases. All have 2 shells, an inner and outer shell.
The first was 2.5mm shells with 0 infill, 1.92mm top and bottom. This was also the only one I got to print without major issues from my extruder.
Second - 1mm shells, 15% infill, essentially creating vertical ribs throughout the print. Also 1.92mm top and bottom
Last - 1mm shells, 0 infill, .96 top and bottom - this was the least successful one I printed, and had one failure where I lost pretty much a few layers entirely, so I saved half of it to test anyways'
Edit: Sitting here looking at the prints, I don't think Cura actually sliced them to the requested shell widths, they all seem to be around 1-1.2mm shells inner + outer, I'll have to look into what its up to

Why Nylon prints are cool:


My suspicion was that the nylon would in fact flex and deflect fire, but that they would end up splitting on the layer lines, especially given my cooler and draftier printing environment leading to less layer bonding than I would like. Ideally they wouldn't split on the layer lines, but I had ripped apart a few test prints with some leverage already and seen some bad layer bonding in spots.

Now, how to test? Destructively of course! Whats the most destructive but accurate test I can think of? Point blank range behind the dual sterns of my Derfflinger of course!

I didn't feel like taking a lot of time to rig up a way to mount them, so I just set a 12AH lead brick on top of the subject to hold it in place. for some things this is probably more resistance to movement than the piece would have once mounted on the ship, and I figured it might increase the damage, but hey, we're trying to damage things here.

First up was the 2.5mm shells.

After 3 blasts from the dual sterns the horizontal band where the impacts are occurring have split at the layer lines above and below. Not the performance one could hope for, but other than the split, the nylon shows no damage. I turned it around and shot the other side. Took half a dozen before the separation began.

So I moved on to the 1mm shells, 15% infill. The first side took 6 blasts before the split, only this time I noted a few spots where the split changed layers, indicating I likely had underextrusion issues affecting the layers cohesiveness. I spun it around and it took 10 on the other side, this time actually breaking through and making a flap of the two layers.

1mm shells, 0 infill. These didn't hold up for long. The layers separated after being hammered only twice. Since I was already having issues with this one separating from starvation in the lower layers, I didn't bother to test the other side.

I still had a 1mm shell, 0 infill upper half to test. Thinking it might be an interesting test just as an open top wall I set it upside down, with the half facing the guns free to flex by shifting the lead brick to the back half. I didn't really count, I just hammered at it till I saw a visible result. At this point I know it'll fail, I just want to see how.

That's kind of neat.

For a lark, I took one of the bottom layer pieces and set it up against the guns, backed by some wood and my lead brick and firing into it.. for absolutely no effect. I didn't bother taking a picture.

Lastly, what the heck, we're here and I apparently still have some bbs left, so i plunk the poor little whaler in front of the guns.

Apparently I only had a single shot left in each gun, and the little whaler went for a flight. No damage that I could find on recovery. Not being properly secured to anything likely prohibited it taking any real damage anyways.

 

I'm going to try to tackle my extruder problem and then try again, this time I'll go with solid walls (they seem to measure around 3mm thick total?) and repeat the exercise. I'm also going to try some smaller details and adhere them to a testing surface, and then rake them with fire and see how they fair. Bollards and boats and such.

Lessons I've taken away so far:
Nylon is super flexy and that makes for some fun potential - and incredible damage resistance if the bonding can be improved over what I had in my first go around.
Nylon is super stringy which may be an issue if the internal spaces are important to you, check the path the slicer makes closely.
Nylon needs to be printed slow so your extruder can keep up the feed.
Destruction is still fun!

The stringy nylon 'drool' from the printhead moving is so flexible I've been trying to think of ways to replicate it consistently and make use of it, just because it is that neat.
The experiment with firing perpendicular to the bottom layers, and their complete lack of damage from it, has me thinking of the potential to assemble printed sheet pieces into structures and armored features (casemates?). More work, but if fire doesn't impact the layer edges it can't attack the weakest spot...

 

Yeah, I figured out that the most it was giving me was 2 passes per shell, so cheating a bit with the expansion characteristics, 1.2-1.3mm at most per shell. I just finished the bottom 3/4 of one (bowden tube popped out before it
finished and it ran a few layers with no extrusion so I killed it, guess i didn't have the little retainer all the way in) that is 100% infill, so basically the full thickness, going to take some shots at it this weekend and see how it fares.

I know ABS can be printed with enough thickness not to crack, but I'm hoping with the nylon to avoid even the denting if I can. Then its just a matter of touching up the paint. I don't think its very practical for large pieces though like the QE superstructure that @Tugboat is doing given the slow speeds.

 

You might try running the hot end temp up 10C and see if printing a bit hotter helps reduce the interlayer separation...

 

The Night of Destruction continues... I clipped the cover to a piece of wood and then clamped it in place to simulate a turret cover or wall attached only by its base and let loose with the point blank twin sterns again.

Took about two dozen shots (so roughly 48 full power impacts all pounding pretty much the same spots) and I got layer separation again. No other visible damage though.

I can run up some more, but I'm already at 250 and not sure how much more I want to go up

Overall i am pleased at the potential here, but i have to address the layer issues. I might be able to help by getting the ambient temps in my printing area up and reducing drafts so the part will cool less, in addition to deciding how much hotter im willing to run

 

Ron, the issue for Nick not wanting to go hotter is overheating the PTFE in the hotend, not the nylon. This limitation is why people are slowly migrating to all-metal hotends like the E3D.

 

This is exactly my concern.

I had that exact problem in ABS and PLA on kapton alone which is why I printed them with brim initially with the nylon. I'll give them another go with 0 brim later, just to check it, but the nylon seems to stick to that glue stick glue like a nail to a lodestone, and I haven't always been getting the z-zero as low as it should be on the first layer.

 

No, I have not yet. Diminishing returns after a point. I have an all metal e3d v6 on now though, I could try printing hotter. The nylon stinks though and I don't relish fighting with its feed problems again.

 

I've tried the PCTPE. Seems pretty damage resistant, but at about 40$ for a pound I haven't been wild about printing a much to test thoroughly yet. It certainly doesn't qualify as 'el cheapo'. It also exhibits some warp characteristics which is frustrating and annoying.