Printing a Nylon part with dissolvable PVA as support material

[tvaughan34 1]

Hello,

I am new to printing with Nylon, but I heard it is best/strongest for production parts, so I am testing it out. I am trying to use PVA as a support material and then dissolve it away afterwards. However, Nylon is hydroscopic so I am having issues. At first, the PVA dissolved away fine and the print worked well. After a few days, the nylon (which I now assume had water absorbed internally still) became very soft and weak and broke very easily.

My question is, if I want to use Nylon with a PVA support material, can I soak the print in water, and then dry in it an oven right after and not lose any strength? Or is it a case of Nylon never having the same strength after soaking it in water, therefore making Nylon and PVA an incompatible print combination.

ABS warps a bit too much for some of the parts I am using. PLA seems a bit too weak. I also have CPE, but my understanding is that CPE is used more for high temp applications.

Thanks for any advice or tips in advance!

Taylor

[gr5 2,265]

Nylon and ABS are a whole level harder to work with than PLA. It took me about 100 prints to feel really comfortable with PLA and then another 100 to feel comfortable with ABS. I'm still not comfortable with Nylon.

I have printed nylon with pva support and that works very well. Even better than pla with pva support. I soaked the part for about 24 hours and it did not affect the nylon in a bad way at all. I did not dry the nylon in an oven or anything. Besides it only takes a day or so to reabsorb water from the air.

I have no idea what you mean about the nylon getting "soft and weak". Was it in heavy usage? Did you use it for a gear or something? Nylon is much more flexible than PLA or ABS. If you use it to make say a link in a chain that is a good thing as it distributes the forces better and makes it as strong as hell. Much stronger than a chain link made with PLA or ABS. That is not so good for say a quadcopter arm or a gear. Or in uses where it gets above 90C due to friction (even if only the thin skin surface of the part gets to 90C it's a problem eventually).

PLA should be stronger than ABS for most cases (it's complicated). The main problem with PLA is not strength but that it can't handle > 50C very well. If you need higher temp but want a material almost as easy to print as PLA then go with nGen.

If you want something you can drive a truck over, then nylon is best. It is soft so it will just flex and return to normal after. No damage done. You can drop nylon parts off a tall building and they probably won't get damaged when they hit rock. Not so true with ABS or PLA.

For warping of ABS I can definitely help you there but I recommend staying away from ABS. Fixing the warping issue is easy. Making it as strong as PLA is hard. Very tricky. In fact you will have to do some destructive testing until you know that your ABS is bonding properly. There's no other way to tell. With PLA it always bonds properly.

[tvaughan34 1]

Nylon and ABS are a whole level harder to work with than PLA.  It took me about 100 prints to feel really comfortable with PLA and then another 100 to feel comfortable with ABS.  I'm still not comfortable with Nylon.

I have printed nylon with pva support and that works very well.  Even better than pla with pva support.  I soaked the part for about 24 hours and it did not affect the nylon in a bad way at all.  I did not dry the nylon in an oven or anything.  Besides it only takes a day or so to reabsorb water from the air.

I have no idea what you mean about the nylon getting "soft and weak".  Was it in heavy usage?  Did you use it for a gear or something?  Nylon is much more flexible than PLA or ABS.  If you use it to make say a link in a chain that is a good thing as it distributes the forces better and makes it as strong as hell.  Much stronger than a chain link made with PLA or ABS.  That is not so good for say a quadcopter arm or a gear.  Or in uses where it gets above 90C due to friction (even if only the thin skin surface of the part gets to 90C it's a problem eventually).

PLA should be stronger than ABS for most cases (it's complicated).  The main problem with PLA is not strength but that it can't handle > 50C very well.  If you need higher temp but want a material almost as easy to print as PLA then go with nGen.

If you want something you can drive a truck over, then nylon is best.  It is soft so it will just flex and return to normal after. No damage done.  You can drop nylon parts off a tall building and they probably won't get damaged when they hit rock.  Not so true with ABS or PLA.

For warping of ABS I can definitely help you there but I recommend staying away from ABS.  Fixing the warping issue is easy.  Making it as strong as PLA is hard.  Very tricky.  In fact you will have to do some destructive testing until you know that your ABS is bonding properly.  There's no other way to tell.  With PLA it always bonds properly.

First of all, thank you for your detailed response. The part I am trying to print from Nylon is an interface between a linear screw actuator carraige and light load of less than 1lb. I will try to upload my solidworks model or .stl file when I am back in the office tomorrow.

I printed two of these pieces. The first one failed 80% of the way due to pva not extruding. The second one I got the PVA to properly extrude and it came out well. I soaked the second/completed print in water to dissolve the pla (probably a week ago). Today I was messing with the actuator and noticed the nylon actuator interface piece was extremely weak. Flimsy, very soft, and bendable to the point I broke it pushing on it pretty lightly. No way this would have happened right off the print. I compared it to the failed piece which was nearby, and it was a world of a difference. The failed (non-soaked piece) was still hard as a rock and not bendable or flimsy.

The piece in use was in the same enviroment as the failed print, with very little usage/wear on the completed print. Only difference was that I soaked it in water.

I then came across another piece which I soaked the previous night (nylon with pva support, no production usage) and it seemed "swollen" and distorted in every direction. The piece looked nothing like when it finished printing the day before. Also noticeably softer/weaker.

I was very suprised I could not find more info on this topic, but it seems most people dont have this problem? Perhaps the industrial water I am soaking the nylon in contains a chemical that affects it?

I am at a loss as to what is going on. FYI I am using an Ultimaker 3+ Extended with Ultimaker spools.

Thanks again.

Taylor

[gr5 2,265]

This is very strange. Maybe you got a bad batch? Maybe the "nylon" is actually pva? But if it was it would be completely gone after a day or two.

I have only done I think one nylon/pva print and it came out amazing. I had to soak it a long time - I think 12 hours. It's still in great shape now - about 6 months later. I have done many nylon prints without pva. But I was so impressed with the nylon/pva combo. More than pla/pva combination.

Maybe soaking for more than 20 hours is a problem?

Maybe you got a bad batch of nylon? You can certainly dry it quickly - it takes just a few hours in the oven - I forget temp - but around 90C should be good.

Maybe you have some kind of acid or something reactive in the water?

Oh I just realized - one nylon part I printed - it's in a bathroom - in the shower. There have been easily 50 showers with water splashing on the nylon part each time. It's still as good as new.

[gr5 2,265]

What you describe by the way sounds like pva. You soak it in water for 10 hours and it gets very very soft. And you can just pull it apart like snot.

[tvaughan34 1]

What you describe by the way sounds like pva.  You soak it in water for 10 hours and it gets very very soft.  And you can just pull it apart like snot.

Definitely not PVA. The actual PVA dissolves and pulls apart like snot. My "nylon" holds together but just becomes very soft, bendable, and seems to lose most its strength properties. Doesn't completely fall apart however.

[geert_2 558]

Nylon absorbs a few percent of water, but then it should stay in a sort of equilibrium. And it definitely should not dissolve or decompose. A lot of clothing is nylon, and you can wash it without it falling apart. Also in industrial all-weather applications, you often find nylon blocks and rods being used for bearings. I have seen them here in automatic bridges from ships to the wall (dutch: "loopbrug").

Are you sure you have real nylon? I seem to vaguely remember that there do also exist some sorts of "biological nylon", based on plants instead of on mineral oil, which might indeed decompose? Maybe you need to google into that?

Or maybe you use incompatible lubricants in the system? In model trains I have seen nylon gears swelling (just swelling so they would not rotate freely anymore, but no decomposing), but that was due to incompatible oils.

Also, maybe you could ask your maintenance staff what they use in the industrial water? Usually this is just plain tap water and collected rain water that is stored in a big tank and recycled, with a desinfectant added (chlorine?) and or with UV-light treatment to kill bacteria? It shouldn't be corrosive, since then it would eat away all rubber seals too. Unless you would work in a recycling environment where they do clean sewer waste water by using plastic eating bacteria, and your watertank has been infected with these...

[kmanstudios 1,120]

I have not seen this with my nylon prints. I am with gr5 to see if you got a spool(s) that are inferior. Mistakes do happen in the manufacturing.

For instance I have 3 spools of PC, all labeled transparent, on the box and on the spools, and one is the black PC material in actuality despite all the labels.

I also have some Cheetah and Armadillo and I swear they print, feel and behave the same way.

but so far, my nylon prints are not problematic.

[Gigi 43]

https://ultimaker.com/en/community/39568-printing-large-parts-with-nylon-and-pva?page=1&sort=#reply-179522

[geert_2 558]

I have a spool of Ultimaker nylon, but I haven't printed with it yet.

Out of curiosity I cut off 10cm of filament and put that in water for a couple of days. After some time it does get more flexible, and it gets a sort of waxy feel: feels more like low-density polyethylene (LDPE) now than like nylon.

A lot of 3D-printing materials are chemically modified for easier printing, to have less warping and better bed adhesion. Maybe one of the modifiers changes properties in water? Maybe one of the UM chemists could shine a light on this? I guess other brands may show similar changes?

Since this is just one strand of 2.85mm filament, not printed, I don't have any idea what this would do to the strength of a print, and to layer bonding.

I am gonna dry it at 60°C and see if it changes again.

Edit: it has been drying for two days now, and it seems to recover to its original stiffness. At least to my subjective feeling, since I haven't done any scientific strength tests.

Edited May 24, 2017 by Guest

[AreDigg 8]

Nylon does not like acidic or hot water, but clean room temperate water should only swell it slightly.

[JstWantoRide 2]

Sorry to bring up an old post but I am having this same problem. My nylon is extremely soft after soaking the PVA off of it.

Info:

I completed my 30ish hour print of UM Nylon and PVA. I did not thoroughly test or examine how hard/flexible it was as I did not know this would be an issue. I put it in a 5 gallon bucket then added water until there was about 2 inches of water over the part. The part floated to the top but did not stick out above the water so I let it float. I did not time it but it sat in the water for about 20 hours. The PVA completely dissolved and the part looks great but is very flexible and weak.

The bucket has been in my shop for many months and could have been used with anything. It looked clean but I did not wash it.

I noticed bubbles in the water when I pour the bucket out in the sink after the 20 hours. I figured that was the PVA dissolved in the water. But maybe there was some soap or something else in the bucket.

I am going to print again and pay more attention to how the part comes off the printer. Wash the bucket, and keep the part in for only 12 hours. I will post my results.

[gr5 2,265]

This is a fascinating issue to me.

Maybe an UM material engineer has ideas.

@Tomhe - does UM Nylon get softer if left in water for 24 hours? Or would this happen if the water was acidic?

@SanderVG - can you make sure Tom sees this thread please?

[SandervG 1,521]

@Tomhe is on a holiday right now so it will be (I believe) not until next week until he can read it.

@JstWantoRide, do you have a photo or any other way to determine how soft your print exactly is? That could help us determine if it is way beyond how it should be or what. On our site it says the following about Nylon: 'Good corrosion resistance to alkalis and organic chemicals'. I dunno what could affect Nylon that way. What does the surface look like? With holes or still intact?

[JstWantoRide 2]

I did what I said and the print came out the same, I even used distilled water in case my water had something in it. My part is thin so maybe this is normal for Nylon and I am used to using ABS.

@SandervG I can send you the part to print and we can perform the same test. Could you do that?

[kmanstudios 1,120]

Have you tried to anneal it?

[SandervG 1,521]

Sure, I can do it. Can you send me a dropbox link?

Nylon by itself is more flexible than ABS, but we can compare

[KristelB 5]

I would try to anneal the part as has been suggested:

After the removal of the PVA, to fasten the removal of the excess water, heat treat your model for 4-6 hours at 75C (Warning: do not use a household oven). You could use your buildplate for this as well.

Thin parts of Nylon can be very flexible and this increases after a water treatment. However, it does not dissolve like PVA does. Your part will improve again after the annealing procedure.

If you need a more rigid part, you can also try to print it in CPE in combination with PVA.

[gr5 2,265]

Thanks kristel!!! it's good to hear from a real material engineer!

>My part is thin so maybe this is normal for Nylon

Okay - that I think is the main issue. Nylon is quite flexible. If you print parts with thick sections then you might not notice so much. But Nylon is sooo much more flexible than PLA or ABS. That's mostly what makes it so strong and tough - you can usually drive a car over a part and it will just flex and bounce back to normal after.

It's not the tensile strength that is impressive about nylon. It's the flexibility combined with almost the same tensile strength as pla or abs. Never fear dropping a nylon part onto a hard floor. PLA - be a little more careful.

[JstWantoRide 2]

Thank you @KristelB! I put my part on my build plate, set the temperature to 77C and let it sit there for 6 hours. The part is perfect now, much less flexible than before but still a little more flexible than my ABS part. This is what I expected Nylon to be like.

Thank you all very much!

[titaniumapple 4]

I think this is an Ultimaker Nylon problem - I have used Nylon12 from Rigid.ink and it's WAY better, it performs like you would expect Nylon to perform.

I have found Ultimaker Nylon to be far too flexible, I printed a UMNylon cylinder with a flat base and UMPVA supports and after soaking it in water the flat base warped into a convex shape!! Rigid.ink Nylon12 is much stronger and stiffer.

[KristelB 5]

I think this is an Ultimaker Nylon problem - I have used Nylon12 from Rigid.ink and it's WAY better, it performs like you would expect Nylon to perform.

I have found Ultimaker Nylon to be far too flexible, I printed a UMNylon cylinder with a flat base and UMPVA supports and after soaking it in water the flat base warped into a convex shape!! Rigid.ink Nylon12 is much stronger and stiffer.

 

Please note that Ultimaker Nylon is based on Polyamide 6/66. It's therefore normal that the properties are different than Nylon12 from Rigid.ink. The choice of one of these nylons will depend on the application.

[Ajformosa 0]

I’ve had similar issues with nylon parts when washing PVA away with warm to hot water at pressure.  Room temp low to no flow, fo sho

[ov_darkness 0]

It's normal for polyamides to absorb water more in elevated temperatures.
PA6 and 6/66 or6/69 will have much larger water absorbtion ratio than PA12 or PA11.
Absorbed water molecules work like a grease -enabling long polyamide molecules to slide - thus it become more flexible.
That's normal and inherent property of all polyamides - but in some more pronounced than in others.
If it's an issue - design around that or choose other material.