Nylon and other high temp plastics - share your experiences and tipps

After printing solid nylon parts for a while now I wanted to print parts with "normal" infills as well, as this turned out to be an unexpected challenge I thought I share some of my finding so others can save on time and filament.

If you read postings about nylon you might start to think it is the worst material out there you you can use for printing.
Partially this is actually right but it just the way this material is.
To clear things up:
Using a 0.3mm nozzle on a very old Stuffmaker mega prusa.
No fancy things like heated bed, special extruders or hotends - just a E3D knockoff for under 20 bucks and a glass plate.
And to stick with these poor basics and to stay in budget 3mm trimmer line is used here.

The biggest drawing card for nylon is the strenght and that it is not reacting with most harmful chemicals we have in our workshops.
On top of that it is also "self lubricating", meaning moving parts like gears or bushings don't need oil.
Impact resistance is on top of the board as well as flexibility in terms of bending without breaking.
But all these good things come at the price of bad handling properties while printing.

Some "myths" about nylon printing:
It is very hard to make it stick to the bed - well not really if you use the right glue.
Layer peeling can only be prevented with a heated bed and a closed build chamber - must have missed something as I work on cold glass with an open frame printer.
You need to dry it and once you think it is dry repeat it several times - did that, been there, don't really bother anymore with drying (more further down).

The facts about these myths:
Nylon does not like to stick to anything, that is true because of the chemical and physical properties of the material.
However on the bed the first layer does not bond like PLA or ABS through a sticky plastic, nylon needs to either melt into the material or it needs to be soaked it (like on cardboard).
Stuff like Bakelite allows nylon to bond with the resin inside while the fibers prevent the nylon from destroying the material - but Bakelite is extremely high temp resistant anyway.
Clear craft- or puzzle glue (alcohol as the solvent) works in a similar way.
Once dry it forms a thin plastic film where the nylon can melt into.
The dreaded layer peeling during a print or very poor layer bonding are only caused by bad print settings and nothing else - again I print on a cold bed with a totally open printer.
The drying is something that should not be required at all.
Nylon comes vacuum sealed and should be dry already (trimmer lines should get an initial drying though .
Unless you are in a very humid enviroment and leave the filament on your printer for weeks on end it should be fine.
Store together with a good amount of indicating silica gel and all is good.
I will explain more of this shortly.

So, how to actually print nylon with success? - Understanding the physics....
Seriously the best way is the same you use to avoid speeding fines, you go slow.
For me that was quite hard to understand as my solid parts printed perfectly fine with speeds of 50mm/s and higher.
But after reading up on the physical properties and how they are affected by temperature explained a lot.
Don't worry I won't repeat it all....
Long story short: Nylon is not like other plastics in terms of the higher the temp the more it turns to a liquide.
Sadly nylon has no real "soft spot" that makes it flow easy, it goes softer but once it is going to get really soft it starts to boil!
Boiling or bubbling nylon is the reason why basically everyone insists on totally drying it.
In theory this a right thing to do, in reality often a bit too much.
If you other filaments don't show moisture problems in your print enviroment than nylon does not need more than an initial check and drying.
Proper filament comes sealed with a bag of silica gel so it will be dry, trimmer line should be oven dried for a few hours or packed with a good amount of fresh silica gel for a few days.
You can check if your nylon bubbles from high temp in the nozzle or from water content quite easy.
If the nylon is dry and you extrude it quite fast the bubbling will stop and it comes out as a nice and clean string.
With water still in it this string will show exploding bubbles while coming out.
Once left hot in the nozzle both wet and dry nylon act in a similar way.
The dry nylon with come out bubbly and foamy but it it will not show signs of steam! You might still hear a crackling or boiling sound though.
Wet or moist nylon will bubble too but while doing so it also produces steam as water is forced over the boiling point inside the nozzle.
So you hear puffing noises and (especially when using a strong light) can see steam as well.
I think this weird "feature" of nylon is what is causing all the confusion about drying it....
At this point some of you might already realise that due to this boiling in the hotend we face another problem, but that comes next....

So, how to actually print nylon with success? - Basic extrusion calibration....
Problem with nylon is that it expands and shrinks not only while printing but it can be "pressurised" as well.
As with water in your pressure cooker, this means the boiling point for nylon (both dry and moist) changes with nozzle pressure!
Sounds to make thing complicated? It does
You already have working print settings for other materials of the same diameter, use your best as start but do not even bother if you can't get really decent prints in PLA and ABS.
Temp references go from exact values like 242°C for some fancy products to useless refences stating "230-270°C depending on print settings".
I am not going into bed calibration, adhesion or other basics.
The key is speed and flow rate.
So we cover that in the next step, for now just increase the extruder temp until the nylon starts to slowly bubble out of the nozzle - this temp is your baseline!

So, how to actually print nylon with success? - Actually printing it!!....
Start by printing a solid testcube of your choice with a layer height of 0.1mm, 0.2mm for the first (or higher if your bed requires it).
Speed settings about 50% of what gives you really good prints with PLA.
Did I mention SOLID? Meaning 100% infill or for Silc3r, Solid infill every single layer.
This will give you maximum pressure and the least pressure drops inside the nozzle.
Watch the layer forming and adjust the extrusion multiplicator until you get nice and smooth infills for every layer.
If you can't adjust the rate on the go, abandone the print, change multiplier and start over again until it comes out perfect to the top layer.
You now got the correct multiplier for 0.1mm layers - if you need higher layers as well you shoul save the profile and start over as nylon often needs different multipliers for different layer heights.
If during these prints you notice a foam like surface quality even though your nylon is totally dry then you have to increase the print speed a bit.
If you first layer does not come out clear but foamy once the skirt and brim are done decrease the temp until it does.
Quite often at this stage you encounter the problem that perimeters look bad while the solid infill looks great.
Check the speeds and try to get them all on the same level, extrusion widths should also be all the same.
As said nylon behaves not nice if something like movment speed or pressure changes
Once the solid cube looks great repeat it with two cubes and increase the print speed until the quality suffers.
You might have to increase the temp if you have bad bonding first
Printing 100% solid means you should have the least amount of troubles with nylon, so if possible use this to your advantage.

Before we move on to printing normal models with less than 100% infill a word on speed, pressure, extrusion width and model sizes (details)...
The one thing you don't want to do is printing fine details or tiny parts with nylon.
As long as you are working with 100% solid models this is only an issue in terms of having enough objects so they can cool down between layer changes.
But normal prints can drive the operator into sanity (assuming we are already insane trying to print nylon) as the former prefect testcube might come out as a fluffy, foamy spongue instead of a clean looking cube.
Nylon simply does not like very short print moves and it really needs enough pressure and time to properly bond!
Where a lot of people dry their nylon again and again without getting rid of the bad quality we simply reduce our speeds and accept the limitations so other materials can be used where possible.
3 perimeters are a working value for most materials, for nylon you should consider 5 to get a really good surface and good strength.
With just 3 perimeters the first two only define the basic outline and only the last perimeter can provide accuracy - that does not leave much for the increased needs of nylon
We all want to print as detailed as possible, so we use extrusion widths as thin as possible, at least for our perimeters.
Again, nylon is different, to give it enough time to bond and also enough pressure for this a wider extrusion is much prefered.
So if 0.36 work just fine with PLA use at least 0.4 for nylon.
You can only build up pressure inside the nozzle if the filament has nowhere to go.
For our infill this means disaster and is the reason why so many people complain it is a pain to work with.
But partially the same is true for our outer most perimeter - there is nothing to stop it from expanding to the outside!
At this point we can start to run in circles trying to get at least a semi-decent print....
Whatever you do or change always keep this mind while tweaking:
Nylon starts to boil if it is too long in the melting chamber, especially if there is no pressure!
Means you always have to make sure the flow rate when printing areas without nozzle pressure is high enough!

Ok, let's finally try a normal print for real
If you soild tests got to really good, high speeds - forget everything about these speedss right now.
Normal models that require good bonding and bubble free extrusions throughout the model need turtle or even snail speeds to come out properly!
Did I mention the weird properties and special needs of nylon already?
Seriously though, once there is nothing to keep the pressure up in the nozzle the speed and temp need to be drastically reduced.
For example I can print a 20x20mm testcube solid with 60mm/s or more @ around 270°C.
Trying the same settings on the same cube with just 20% infill and all that comes off the bed is a fluffy mess.
To get the right and totally different settings for normal models we have to first reduce the temp and speed.
Heat up to the high temps that worked great on solid models and turn the extruder by hand.
Now reduce the temp and check how much harder it is to get the filament through - you don't want to break or overheat motors while printing so take your time.
Try to get the temp as low as possible to prevent boiling in the hotend.
For me that meant going as low as 232°C.
With this temp as the baseline for all after the first layer which should still be printed hot so it bonds, you can try a testprint of the cube @ about 20mm/s.
The first layer will still be looking perfect, if the second has problems already increase the temp by 5°.
Use the first solid layers to adjust the speed for a clean print with good layer bonding.
Once they look clean and bond well to each other move on - so until now no need to finnish the test cubes and waste filament
You might have to go as low as 15mm/s for the speed and the temp range should be between 230° and 240° - lower if the solid layer show bubbles or look foamy.
The line width for the normal infill might need be set up to 55% higher than the thinnest working perimeter as otherwise you only get dots instead of lines.
Using infill patterns like honeycomb is prefered for nylon as here we don't one layer gaps between the infill lines - drastically improving the look and binding of the infill.
Once you reach the first solid top layer you will find out if you need a more dense infill or if you prefer more layers to get a good finnish - depends wether structural strength and / or stability of the top is important.
In any case be prepared that you might need a few more layers to get a prefect finnish as first you need a good solid base under the last layer.
With a 20mm testcube that is reduced in height to a few mm you can also check if the bridging works.
This is the final clue for the temp and flow rate as here we have nothing at all to help the nylon stay in place or to stick to something.
I still find it very hard to get this right as due to the nylon properties all settings that worked fine before are void.
And you can only tweak the flow rate and speed for the bridging.
Big overlaps, even lower speed and flow rate tweaking until it looks usable is my best advise here.
Depending on the bridging length and how much space is left for big overlaps running realy fast can help bridging with nylon.
With a reduced flow rate and really high speed you can form spiderweb like lines instead of a "solid" bridge, with low layer heights it can be enough the support the next layer - if the bridge is not too long, then it will just sag and fail.

What to do and what to avoid at all costs.....
As said, solid is better, so if you can print your nylon model solid - it really does give the best results!
Do not forget that a change in layer height might need adjustments of the extrusion multiplicator, so use the infill at every single layer and don't skip it to save time.
Avoid fine structures, best example I can give is a house key.
There is not enough width in the model to allow for proper bonding. And don't mean the general height of the object but the details at the working end.
At all costs avoid single structures!!!
Pillars as a support or model details that are less than 4 times the extrusion width will give you a headache!
There are lots of models out there, like dragons and statues that have fine details like spikes, fingers or even flag poles - they won't print properly unless you have a lot of time on your hands.
If you have problems getting the settings right always start with the lowest possible temp and speed to work your way up - never start at insane speeds that caused a fluffy print.

The all important first layer, heated beds and fans - a little extra...
Before you start messing with the heated bed get the nylon to print without it!
You don't want to mask issues with a heated bed that might cause you headaches once the print hight is out of reach for any benefit of the heated bed.
If in doubt print your test objects on a piece of cardboard to make the first layer stick.
Unlike other filaments nylon does not forgive you any mistakes, so the first layer should be as close to perfect as possible.
Over- or under- extrusion caused by a wrong first layer calibration can haunt you through the entire print depending on the part you do.
If the first layer is impossible to get perfect because the bed isn't either, the second layer should correct most of it and the third must be flat and even.
I am still not sure if a cooling fan on is better than a cooling fan off.
For solid parts it does not matter too much but a lot of detail and finer structures will benefit from cooling as nylon can store heat for quite some time.
Again, use the extras of your printer only to improve things but not to make them possible!
If you need 120° on your bed to make a testcube stay intakt without peeling than your print settings are simply wrong


Warning when using trimmer line!!!
I just wanted to try a new, yellow line and noticed that it was extremly stiff compared to the other nylon I used so far.
The one now was given to me for free as a sample of just a few meters.
After cutting it I noticed it one of those "core" lines where you either have a special material in the center or a harder coating on the outside.
I did a check with a lighter and a piece of nylon on an old spoon.
The inner core has what I think is glass fibres in it.
Might still work fine in a 0.7mm nozzle but not risking it on my standard 0.3mm one.
So as good advise to prevent painful clogging or even fatal hotend failure test your trimmer line before use!!!
Heat it up until it goes very soft without burning and spread it around - if it feels crunchy or you see "hairs" sticking out do not use it in your printer!!
I used several trimmer lines with special coatings or core materials and the results are often really good but using something that has other stuff than plastic in it can not be good for the hardware.

Edited 1 time(s). Last edit at 12/21/2015 07:42PM by Downunder35m.

Hi DU,

thanks for writing that up, it was an interesting read. I couldn't resist the temptation to have a go with some spare trimmer line I had. Pretty pleased with the initial results, even if it is just a 20mm test cube.



Settings were: single perimeter, 0.28mm layer height, 0.6mm width, 247C extruder, 85C bed, and a very tedious 15mm/s print speed.

Inter-layer bonding is still poor though - it broke as I took it off the bed

Edited 1 time(s). Last edit at 12/21/2015 10:58AM by JamesK.

I pushed the temperature up a few degrees to 251 and that seems to have made all the difference. I tried out your suggestion of using honeycomb infill, with all the widths and speeds set to the same values to try and keep a constant extrusion rate. This test was going really well until it started on the solid top - I'd forgotten to set the bridging speed so it leapt up to 60mm/s and promptly jammed the extruder. This yellow filament is only 1.2mm and so it readily bends and folds up between the gear and the throat if the extrusion rate (and hence feed pressure) is too high.



Getting over-excited, I decided to hit the local shops and see what other trimmer line was available. Turns out trimmer line is 'seasonal', and this isn't the season, but I eventually managed to track down some 1.6mm blue filament. It works a treat, and looks rather good too

This thread was great timing, as the next thing I want to add is a pair of part cooling fans. Unfortunately, the fan duct is rather tricky to print in pla without a fan duct (!). It gets too hot at the top and fails in a gooey mess. I was able to print a pair of them in nylon with only minimal stringing between the two which easily cleaned up with a sharp blade. Once I work out the design for the mounts I'll do those in nylon too, and then I wont have to worry so much about them getting warm and softening.



I was just reading about the new auto-speed feature in slic3r. It's supposed to maintain constant pressure, so it sounds ideal for nylon - time for more testing!

[edit - fixed typo on max volumetric speed]

OK, so the auto-speed feature seems to work well. I set a default width of 0.6mm and all the other widths to 0, all speeds to 0 except the auto-speed max print speed at 20mm/s, and did a back of the envelope calculation for max volumetric speed at 5mm³/s, and it worked out fine. I gradually increased the feedrate to 150% through the print with no obvious negative affects, so I've revised my max's to 30mm/s and 8mm³/s. I also increased temperature to 255C. I'm printing on glass with Elmers purple glue stick. I'm really pleased with that so far, but I know these are only small models. We'll see how it goes when things get bigger.





Edited 1 time(s). Last edit at 12/21/2015 07:00PM by JamesK.

Nice to see that someone jumped into the cold waters too
That blue looks awesome, much better than my pale green
One thing with bigger prints is that it can be tricky to keep them on the bed.
As a last resort I do a "double print":
First I let just the brim print and stop the print half way through the brim.
Before the real run I increase te brim a bit and put another layer of glue on either side of the half printed brim.
Give a really ugly look if there is too much glue but does help a lot with the sticking.
Tricky bit is to get the stop at the right position as you want it close to the perimeter but not that close so the glue is pushed into the perimeters.
I noticed that most big or slim prints start to peel not because they start to bend but because air is getting between the first layer and bed.
So far really big prints with more than 12cm side lenght and nothing round I actually print the first layer, pause, add very diluted glue on the print and once totally dry I continue the print.
Sometimes I loose the bottom layer when taking the part off but at least it won't pop off the bed premature.

Any chance you have a brand name for that nice blue?
Would love to add a roll or two to my collection

It's Power Care: [www.homedepot.ca]

It's not actually round, although I didn't notice in the shop. It's not a really obvious twist like some of the trimmer lines, but some sort of edged cross section. It doesn't seem to matter as far as feeding through the extruder, but it makes measuring the diameter a bit hit & miss. You have to fine tune the calibration anyway...

Seems I have no chance to get that in AU, would have been nice though.
Another thing I noticed that would be nice with nylon in Slic3r would be to set upper and lower values for the volumetric extrusion in conjunction with the print speed.
Small details or tiny gap fills can be a pain in the §$*'% if the nozzles start moving so fast that the nylon refuses to bond and goes all fluffy again.
So far the only chance here is to lower the overall print speed, which for big models can mean more than doubling the time of an already slow print.
Could not figure yet how to get proper infill, perimeters and fine details in one print with good results.
Where PLA just flows everwhere nylon always needs to be pushed, pressed and slowed down.

Did another test last night without the volumetric extrusion but similar low print speeds.
Result was unusable even after making sure all extrusion widths are the same
The g-code has totally different values too, so I guess Slic3r is using a bit more than just flow rate control to make it work so much better.
Funny thing is that all these extrusion bugs seem to disappear with volumetric extrusion too.
So far I have not encountered a bug in my prints.

Added a little warning to the first posting in reagard to trimmer line with cores or outer coatings.

Edited 1 time(s). Last edit at 12/21/2015 07:43PM by Downunder35m.

I did a scaled down Julia vase just for fun with the yellow line. That one went all fluffy - it's weird how it just flips from normal to fluffy, there must be some wild chemistry/physics going on.

This weird stuff going on is a nylon speciality.
PLA and ABS don't really care too much if they stay hot inside the nozzle, nylon start to "collect" the heat until it starts boiling.
Problem here is that the pressure inside the nozzle is greatly affecting how much it boils.
Retractions are still a pain, even though I was able to lower them down to under a mm.
I don't even bother anymore trying to the sprial vase thing or other thin walled objects, it just does not work unless you work with really thick nozzles (even then it is tricky).

Did you ever try nylon-forming?
Every now and then it hits me and I print a thin sheet of nylon trying to find easy to use ways to put it into shape.
But it is quite hard to impossible to do anything that would require the remove material, like bending the outside of a disc up to form a seal.
Even tried to use it to waterproof a piece of cotton as a test.
Thin material works quite well, like an old pillow case, thicker stuff like jeans requires a mounting block to keep it all flat and under proper pre-tension.
With this and an adjusted start height for the print the fabric is moved around by the nozzle too much.
Would be nice to have a much bigger printer and use nylon to re-inforce and waterproof things like camping chairs - they always fail after just one summer and most of the time you fall through them getting stuch in the frame ROFL

That is a close up of nozzle for a bottle rocket, 35mm in diameter, 55mm high.
Printed with 0.2mm layers @258°.
To get that soft touch surface and an overall more flexible part I used "wet" nylon.
So instead of drying it fully it was actually put in a bag with wet paper for a few hours.
The moisture causes the fluff up which actually helps the layer bonding.
Downside of printing "soft" nylon is that you have to adjust the extrusion multiplicator down a bit if you require accurate parts.
I did an earlier test of this without the inner core and nozzle and was able to squeeze the threaded part that goes onto the bottle without breaking or layers seperating.
Mind you the hole diameter was a bit 20mm and the squeezed wall were touching.
Could be quite nice for parts that require both flex and stability without stretching, where the flex filaments would fail.

This trimmer line is continuing to impress me. I printed up a pair of these brackets to mount the part cooling fans today, and they worked a treat

Is that printed solid or does it really look that good when printed with partial infill?
But I notice you get the solid color for the first layers and then more pale color, same here unless printed 100% solid.
Searched through all the home depot shops around here today to find something like your blue line.
Between 1.6 and 2mm I can get a pale blue one, don't like the color at all.
Nothing blue between 2.6 and 3.2mm, only red, yellow and silver.
Might get a 10m roll of the silver one day to test it but onyl if I can find a supplier with better prices for a big roll.
At almost 16$ for 10m it is quite a bit more expensive than my bulk billed 400m of green trimmer line.
But apart from some problem with big parts sticking properly I think the superior qualities of nylon could make it my default filament for printing.
For delicate and detailed stuff I might use PLA or ABS but for everything that should actually last nylon is the way to go.

Coloring nylon is no problem with acid based colors.
But getting clear or at least natural nylon that is not overpriced for 3D printing is a tuff thing.
Maybe one day I find a way to remove all the color from trimmer line or try to color the green line with some additional red or blue.

Yes, you're right, that pale area is pretty much the only bit where there was enough space for the 20% infill to kick in. The vertical and the yoke is almost completely solid.

The small rolls work out pretty expensive, fortunately this 250' roll works out about the same as buying the real stuff from our local supplier, but I can pick it up from home depot and only have to pay $10 a time which doesn't feel so bad

Enjoyed reading this thread, keep it coming

Quote
chngyian
Enjoyed reading this thread, keep it coming

Well, seeing as how you asked

I'm still really pleased with the prints I'm getting with the blue Power Care trimmer line. I've just been printing some legs for the LCD case. They are 94mm along the long side, and they printed fine with 10% infill. Apart from the slow print speed, I'm preferring the prints I'm getting with nylon to the ones I get with PLA.