Prrinting in Nylon

[HO RacePro]

I have just ordered an all-metal hot end for my Ender 3 Pro printer. Said hardware is required for the high temperatures needed to print Nylon. I already have Nylon filament in house.

I am anxious to try Nylon as a printing material. It is one of the oldest and most versatile of the true engineering thermoplastics. It is especially tough and strong. It is what I make Slide Guides out of.

It is also highly hydroscopic (absorbs moisture). And that propensity to absorb moisture has a significant impact on its physical properties. From the printing point of view it means the filament has to be dry. Otherwise the internal moisture will turn to steam and create bubbles in the molten plastic.

Among other things, it means you can color nylon parts with fabric dye.

So here I go, charging off in a new direction with vast enthusiasm and scant knowledge. I'll be back when I have something to report. The first thing, most likely, will be how the installation of my new hot end goes.

Ed Bianchi

[Wet Coast Racer]

The first thing, most likely, will be how the installation of my new hot end goes.

Indeed, be sure to post pictures.

[MrFlippant]

Set up some kind of dry box.
Also, nylon is worse than ABS when it comes to warping. You'll probably need some kind of enclosure for reliable printing. That can be as simple as a cardboard box big enough to cover the whole printer, or as complicated as a fancy case with clear walls and doors and such.
If your prints are small enough (guides), then you can probably get by without the enclosure, but you'll still want to do everything you can to reduce drafts and to keep the printer nice and warm while it's printing.

[Kevan]

I've been thinking of enclosures for my Ender, I don't like the idea of enclosing the power supply and control panel in that heat so probably best relocating those outside the enclosure.

[MrFlippant]

The control panel will probably be OK, but the power supply is best if taken out of the heat. Nothing wrong with doing both.

[HO RacePro]

I have been using a PrintDry brand filament dryer -- the original model -- to feed filament to my printer. That dryer has features that allow you to feed filament from it while it is running.

I keep the dryer set for 45C, monitored with an old Radio Shack digital thermometer. I don't use the features that allow it to hold and feed a second reel of filament. Instead I place two bags of desiccant on top of the one reel, where they can ride around without interfering with the filament feed. That helps keep both the filament and the desiccant dry. When I am finished I put the reel and the desiccant bags in a one-gallon zip-lock freezer bag. At least in theory that will keep the filament dry.

The desiccant bags are made of fabric and have draw-strings. I bought them from McMaster-Carr. Each bag holds maybe two ounces of desiccant -- which I purchased in bulk. The desiccant is blue when dry and turns white when saturated. I can see the color through the fabric.

The desiccant has always been blue. To date I have had no issues with moisture.

The PrintDry dryers are not cheap. Mine cost substantially north of US$100, But on total it seems to have been a worthwhile purchase. I feel I got my money's worth.

It came with a plastic Tupperware-like container that will hold a 1kg reel of filament. It is designed to be vacuum-sealed, and comes with a plastic pump that does seem to draw a bit of a vacuum.

On total I'm not impressed with that container. I think a zip-lock freezer bag and a couple of desiccant bags probably does as good a job, and a lot cheaper. I use it, but I'm probably not going to buy any more of them.

To date I have not had any issues I feel are due to my printer not being enclosed. But I do mainly print small parts and my basement isn't drafty.

Ed Bianchi

[Kevan]

You can re-use that desiccant, at work we used to stick all the saturated (white) in a low temp oven for a few hours and the moisture would evaporate leaving ready to use blue crystals again.

[HO RacePro]

Thanks for pointing that out Kevan. Yes, desiccants can be restored by heating them to drive off the absorbed moisture. Think of them like sponges. They can be used and re-used indefinitely.

I received my new hot end -- an e3d v6, 24 volt -- yesterday. Very quick shipping from MatterHackers!

It came with no instruction sheet. You can find detailed assembly instructions online. Installation is not a simple process! No less than 31 steps!

I haven't taken the time to read through it all yet. I need to build up my courage a bit. Once I dive into it I'll be committed, and won't come up for air until I finish, or I break something. That's how I do these technical jobs.

One thing I noticed in glancing through the instructions. The nozzle needs to be installed while the hot end is at temperature. This is a requirement that I hadn't been aware of when I replaced the nozzle on my existing hot end. I did that cold, and to date nothing has blown up or melted down.

That hot-assembly requirement has a whiff of urban legend to it. It doesn't seem to make much sense to me. Hot assembly is something that is done when parts need to shrink-fit for extreme mechanical strength or very tight clearance. It can turn a press-fit into a slip-fit -- a good thing when assembling large parts without a huge hydraulic press. Those of us who do their own work on motorcycles are aware of some jobs that require it. But it is not typical for threaded assemblies.

And if there are critical sealing issues I'd expect that a wrap of Teflon tape might be used to fill the interstices. Teflon is rated for continuous use at 260C, and intermittent use to 316C. According to MatterHackers Nylon prints at 260C max, so Teflon tape should be good long-term.

Teflon is also a great lubricant, so assembly of the nozzle to the hot end should work at lower torque -- less likely to strip threads.

But I suppose it's not worth fussing about.

Oh I'll do it... But I'm going to hate myself in the morning.*

Ed Bianchi

* One of Bugs Bunny's racier lines.

[MrFlippant]

You have to ASSEMBLE it cold, but then when you get it warmed up, before running filament through it, tighten the nozzle. Things expand when heated, and there will be a gap created if you don't do the hot tightening. Trust me, this is not urban legend at all. If you don't, there will be slow leakage of material ABOVE the heat block, and it will eventually drip all over your print, or worse, create a blob.

All metal hot ends work differently than the kind you have on your Ender. There's no such thing as hot tightening, but if your PTFE is not properly pressed into the nozzle, then you'll have problems. If you haven't had that happen, then good for you! It's quite common, and there are a lot of things that can be done to reduce the likelihood of it happening.

I'm glad that you will be following the directions on the hot end assembly. That hot tightening step is the one most commonly missed or forgotten, and also the most common reason for problems later on. Remember, back off the nozzle a half turn, tighten the heat break to it hand tight. Then heat it up and finish the job. Some people forget to back off the nozzle from the heat block, and then aren't ABLE to tighten it any more, and end up with a gap they can't fix unless they rebuild it... usually after getting filament all over the place.

As for teflon tape, well, hot PTFE (Teflon) is the whole reason you're moving to an "all metal" hot end... to get PTFE AWAY from the hottest part. If you're ok with teflon tape on those things, why bother switching? Since you won't be exceeding 260, and the PTFE can (supposedly) handle that, there's no reason to switch. Or maybe there is, and that same reason is why you shouldn't put teflon tape on those things. ;-)

[Kevan]

I use a smear of copper grease on the nozzle thread, working temperature of over 1000°C and makes nozzle swaps much easier.

[HO RacePro]

Copper grease, also known as anti-seize. I use it on spark plugs and exhaust nuts. Prevents stripped threads.

The copper is in tiny balls dispersed in the grease. Keeps the threaded parts separated by a very small distance. Since the copper is annealed it will shear long before the threaded parts are overstressed.

There are other grades of anti-seize that do not contain copper, for applications at even more extreme high temperatures.

I've also heard that milk of magnesia can be used as an anti-seize. Rumor has it that aircraft mechanics use it. I bought some once to try, but never have.

Once again, Teflon tape might be a good solution. Acts as an anti-seize, is a gap-filler, and can withstand the modest temperatures of 3D printing.

Ed Bianchi

[HO RacePro]

Let me take that back...

Teflon would insulate the nozzle, reducing the heat transfer that is key to the nozzle's function.

The copper beads, in contrast, are superb heat conductors.

It would be interesting to compare the amount of metal-to-metal contact with and without those metal beads. The fact that the annealed copper beads will 'moosh' when the nozzle is torqued may actually increase the metal-to-metal contact. That might sound counter-intuitive, but at the microscopic level the contact area between hard metal parts is actually very small. Their very hardness makes that so. Softer materials deform more and achieve better contact.

I suspect I am talking far too much on a subject where I have little expertise. I'm going quiet for a while.

Ed Bianchi

[MrFlippant]

Makes sense. You want GOOD heat transfer between the heater core and the heat block, between the heat block and the nozzle, and between the heat break and the heat sink. You do NOT want good transfer between the heat block and the heat break. We want the heat break to stay as cool as possible, so if you were to use something with insulating properties, it would be on that connection.

However, it's not wise to put something in there that has a listed limit of 260, when you're going to be printing at that temperature. Why? Well, there are times when you'll want it to be higher, such as to loosen a clog, but also hot end parts aren't always right on the money. You might set it to 260, but it might actually be running 270. Without a contact thermometer, you'll never know. Better safe than sorry, and make sure anything you're putting into the hot side (e.g. pastes and whatnot) has a much higher limit.

The hot tightening alone requires you to crank it up to 280 or so.

[Kevan]

You don't need extremes to print Nylon, my machine copes with it at 250°C but the bed needs to be 80°C.

Layer adhesion is unreal with Nylon so consequently cleaning brims/supports can be a right royal PITA!

BUT...Nylon has it's place, not sure a Slot car is that place apart from the guide, the problem being printing Nylon accurately as it needs 0.2mm layer heights and 0.4mm nozzle as minimums. I may revisit guides but more along the lines of a traditional guide rather than a modern RTR car guide which is a bit skinny in places.

This guide for instance: https://www.thingiverse.com/thing:1400313

[MrFlippant]

Figured I'd post this here, too...