What is the best nylon/polymer filament for a foldable platonic solid with living hinges?

[1drman]

Hello friends!

Just wanted to ask the professionals about what is the best nylon/polymer blend for a product that has living hinges. There are several brands out there that do not specify the nylon blend. Some I have tried are Nylon Pro, NylonX, Overture, Sunlu, and Taulman Bridge. I found out that any filament with additives such as carbon fiber, glass, etc.. makes the material stronger, but less flexible that plain PA/Nylon. Nylon Pro from Matterhackers works great, but is way too expensive. TB has been disscontinued, so I have decided not to use it any longer. I really liked the properties of TB and wish I could find that in another filament. I have tried Overture and Sunlu as a replacement, but they need annealing after printing. Some of the living hinges crack after printing, but after a couple of days exposed to humidity, they absorb water, become more flexible and dont crack when they are bent. So I'm currently at a standstill as to which is the best polymer to use. I'm hoping someone can shed some light on this issue and potentially guid me in the right direction in terms of what is the best nylon blend/brand for the job. I am greatful for any advice/suggestion that may be related to this topic. Wishing everyone a happy holiday season and new year!

Best,
1drman

 

[btrueblood]

You are talking about 3d printer (fused filament) polymers, I gather from the brand names mentioned.

Most nylons do need to be water conditioned after melting - easy enough to do by just soaking in warm water overnight.

I've always thought polypropylene makes the best living hinges (the act of bending creates a strain-hardened area at the hinge line). The same strain hardening technique is used to make high tensile cloth and rope filament.

 

[1drman]

Hi Btrueblood,

Thank you so much for sharing some insight into this issue. Yes, I am using FDM as a 3D printing method. Polypropylene is a good option for injection molding, but im looking for a budget/user friendly, 1.75 mm BLACK filament like Nylon Pro/Taulman Bridge or similar. The model I am trying to print, does not require continuous bending or repeated back and forth action. Once the hinges are bent to form the intended polyhedra, they stay in that position. The part is printed flat, but then forms into a polyhedra once it is assembled. I hope that makes sense.

I'm looking for plain BLACK, 1.75mm nylon with no additives. Ideally, it would be PA-11, 1.75mm, BLACK, as it offers better elongation at break than PA-12. Please let me know what you think and if you have any advice/guidance as to what path I should take or potential brands you might recommend for the job.

Have a great rest of your day!

Best,
1drman

 

[btrueblood]

I think the toughest part of 3d printing with nylon would be ensuring that the filament is utterly, perfectly dried prior to printing, and then trying to maintain it dry as the print progresses. Wet nylon foams and becomes very brittle if heated past its glass transition point and into the melting zone.

 

[btrueblood]

Intersting you want nylon 11. It is a fact that it's much more hygroscopic than nylon 12, i.e. it would be more problematic to 3d print in a humid environment.

 

[1drman]

Hi Btrueblood,

Yes, I have taken all of the precautions to ensure that the filament is dry before and during printing. The issue is not the humidity, as I leave the filament in the active dryer until the spool is completely used. I also have an enclosure. Sometimes I leave the filament in the active dryer for a week until the printer has finished the spool. Sometimes I wonder if I have left it in the active dryer too long. Maybe you can shed some light on how long I should leave the filamnent in the active dryer after it has reached its drying point.

Best,
1drman

 

[btrueblood]

I don't think you can "over-dry" nylon. Just do realize that after printing, you need to either let the part equilibrate to normal humidty levels, or force it to re-hydrate by soaking in water.