Carbon Fiber Filament Roundup

Why Carbon Fiber Nylon?

The strength and durability of nylon is hard to beat when it comes to 3D-printable materials. The problem with nylon is that it’s difficult to print, and unless you are printing a bulky part with a lot of infill, nylon parts are usually more flexible that what you would want. Designing for the stiffness of PLA or ABS doesn’t always translate well to nylon.

Adding chopped carbon fiber virtually solves both the issue of stiffness, and print difficulty.

Without much debate, when you need to print a strong, durable part on a 3D printer, nylon is the most likely choice. A lot of folks will turn to ABS or PETG when they need a part that is more durable that PLA, but when you need strength beyond what you expect from a 3D printed part,, Nylon is the pretty clear choice. If you’re cleaning to ABS, it’s more likely because its easier to 3D print than nylon, and the trade-off in strength is worth the ease-of-print.

Adding chopped carbon fiber to nylon filament is a game-changer with respect to ease-of-print and reliability when it comes to 3D printing.

The carbon fiber adds stiffness and dimensional accuracy. Standard nylon material can be very stringy, and results in a part with a good amount of blobs and blemishes. Overall, every standard nylon part I’ve tried to print definitely sacrificed aesthetics and accuracy for the added durability gained. Carbon fiber filled nylon like MatterHackers NylonX, improves just about all aspects of the print properties: stiffer, stronger, better looking, more accurate.

 

We’ll look at a few brands offering similar materials: NylonX, CarbonX Nylon, and Markforged Onyx. We’ll also add a wildcard: Priline Carbon fiber filled Polycarbinate, and I’ll explain why that one is in included later.

 

Price

The first carbon fiber nylon material I can recall seeing was from Markforged in their Onyx product. Shortly after, Materhackers introduced their NylonX material, which seems very similar. Carbon X nylon from 3DXTech is similar but uses a different formulation of nylon and claims to have longer fibers embedded, theoretically making for a stronger parts.

Keep in mind that with any of these flavors of filament, they are nylon based and should be  significantly stronger most other filaments (PLA, ABS, etc). You can build functional parts out of nylon, while your PLA parts may function to your surprise. Let’s face it, nobody is that surprised with a PLA part snaps. Keep this in mind when we talk about price.

A budget PLA spool (2kg) can be as cheap at $20. Of course not all spools are created equal, and the carbon fiber filled material is less dense than PLA, meaning you’ll get more parts from the same amount (by weight) of material. Regardless, $20 or even $40 for a 2kg spool of PLA is still a fraction of the cost of the carbon fiber nylon materials. If the cost is so painful, use PLA to create the prototype and iterations of the part, then use a fiber filled nylon for the final product.

Let’s assume carbon fiber nylon is in the budget, here is a comparison between the three brands:

Based on buying ~1kg of material

Markforged Onyx – $189

MatterHackers NylonX – $116

3DXTech CarbonX Nylon – $91

Keep in mind, Markforged material is part of their closed ecosystem for Markforged machines. Though you can purchase the material and use it on other machines, its developed and intended to be used on Markforged equipment. Their high quality premium product can somewhat justify the price, but do consider that since all Markforged printers are essentially locked in to using Onyx, there is not as much market force to drive that price down.

Ease of print

One thing to consider about nylon and even plolycarbinate is that they are hygroscopic, meaning they will absorb moisture from the air. You have to keep them sealed from the air and ideally stored with desiccants to keep them dry. Once the material absorbs enough moisture, you start to see “drooling” from the nozzle, or even here hissing and pops while its printing. All of this can cause inaccuracies or blemishes on your printed parts. In the worse case, you could have pitted walls that simply crumble.

Moisture can be eliminated by using dryboxes for material storage, or by incorporating a drying mechanism like a PrintDry or modified food dehydrator.

Another aspect contributing the the ease of print (or decreased ease of print) is the abrasiveness of carbon fiber. Over time, carbon fiber filament can wear out nozzles, bowden tubes and even extruder gear teeth. Hardens steel options are recommended, and any brass components and bowden tubes should be checked fairly regularly for wear. Since Markforged printers are made specifically for use with carbon fiber, if you’re going to be printing a lot with this material, it would be a good idea to check their user guides for maintenance.

Compared to printing standard nylon6, the added carbon fiber helps a lot with keeping parts from warping, and enabling printing of finer details. Supports break away MUCH easier than compared to nylon, and dimensional accuracy overall is improved and better controlled. The fiber seems to cool the material more quickly, while standard nylon stays molten hot for longer.

These carbon fiber nylon materials do print at high temps, similar to nylon, so that layer adhesion is great, even if the material cools more quickly after being extruded.

Surface finish

The carbon fiber added to the nylon gives.a slightly textured matte finish that actually helps to hide layer lines well. For all three brands, this makes for a finished part that is much more suitable for an end-use product. The chopped fiber does limit the ability to effectively sand printed parts. Sanding the surface causes the material to turn gray and have an ashy look. Unless you are planning to prime and paint your parts, they are going to look their best right off the printer with no additional sanding or cleanup. If you’re not in to post processing your parts with a lot of finishing, its a great choice. If you prefer sanding to a smooth finish, this likely isn’t the material for you.

To sum up, adding carbon fiber to nylon gets it to print about as easily as ABS, but with less tendency to warp and curl. I still used glue stick on PEI to print all three of these brands.

Technical differences

Markforged Onyx material is based on Nylon 6, with a percentage of chopped carbon fiber.
The fiber is in a chopped powder form, so they aren’t making any claims about increased layer bonding or added isotopic strength.

3DXTech CarbonX Nylon uses a “Semi-Aromatic” Nylon, which they claim add stiffness and has lower moisture absorption. They also say the carbon fibers are longer, which theoretically could add strength along the X-Y axis, thought I don’t think we could expect any difference along the Z.

MatterHackers NylonX is based on Nylon12, again with a percentage of carbon fiber powder. There doesn’t seem to be any claim to fiber length with NylonX, so it seems its just adding density with the lightweight powder.

If we assume there is a blend of about 20% carbon fiber partials in these filaments, then the big difference is going to be what type of nylon they use. Since all three use a different nylon, these brands are certainly not just an interchangeable mix of the same material with different brand names. The recommended print temps are slightly different for each, though since they they all print at a pretty high temp, its possibly you’ll get decent results even if you use the same settings for all three materials.

Showdown:

Here are some examples of prints made with each material. These were all printed on a Prusa I3 mk2 printer. Obviously the Markforged Onyx is intended to be printed with a Markforged machine, but for this test, I’ve used the same print temperature as the Markforged, and did my best to tune print speeds, etc, for effective printing on the Prusa.

Onyx: Slight textured surface finish with slight gloss. This hides build layer lines well. The color is a pretty uniformed black, and the surface texture feels pretty smooth.

CarbonX Nylon: Slight textured surface with a dark grey matte finish. The surface feels a bit rougher than Onyx.

NylonX:

Print Quality:

The part printed in Onyx had the best surface finish and print quality. The slight sheen to the surface finish does a great job of hiding layer lines, and and the part feels like dense nylon.

CarbonX Nylon produced a good looking quality part, but does not look as “finished” as the others. The rougher finish and lighter color makes these prints look less like “end use” quality parts compared to the other two.

NylonX also produced good surface finish and quality, only slightly less quality than Markforged Onyx.

Strength & Stiffness

Of the three, CarbonX Nylon is the most stiff and brittle.

You can produce a strong part with this material, but unless you go heavy with the infill and perimeters, the part will snap pretty easily. In my opinion, this material misses the mark on the expected benefit of tensil strength and overall “bend before breaking” that you expected from nylon. The Onyx material and NylonX both do deliver in this area, where the stiffness of the part gives way under pressure, the part itself does not break.

We also saw more sheering and layer delamination with the CarbonX Nylon than the other two materials.

Onyx offers the most “flexibility”, though it doesn’t show visible signs of strain on the part unless it goes through a few cycles of a strong bend (where other materials would typically expect to break). Stiffness is about on par with ABS, maybe a bit stiffer, and you could certainly use another perimeter or more infill for added stiffness. Markforged claims this material is about 30% stiffer and stronger than ABS. I’m sure this depends on the geometry that is being printed. From my crude testing, I can’t find any results that debunk that claim.

Wildcard:

Carbon fiber nylon materials all offer good print quality and strength, but they come with a relatively high price. There are a couple key components to this type of material that I found attractive:

– Prints at a high temp for very strong layer adhesion

– carbon fibers add dimensional accuracy and reduced warping (Easier to print)

– Looks great, hides layer lines.

During my research on this material, I came across an affordable carbon-fiber-filled polycarbonate, made by Priline. I decided to give this material a try, at least to see if it was a worth low-cost alternative.

Here is what I found with the Priline carbonfiber PC:

• layer lines hid reasonably well
• High temp printing, great layer adhesion
• Low warping, but not quite as easy to print as CF nylon

The price of the CF polycarbonate was less than half of the carbon fiber nylon materials tested. The major difference between the materials is that the PC material is very stiff and not meant for use where you want to flexibility. Nylon by nature is resilient and able to bend before breaking.

Even though the PC material is very stiff, I’ve found a many parts work out just fine with this level of stiffness, and in affect, carbon fiber polycarbonate seems to be a good choice if you’re looking for a finished part that is similar in stiffness to PLA, but is Much more durable.

Polycarbonate is also hygroscopic, so you have to make the same accommodations for keeping the material dry.

The finished product printed with Priline CF PC is pretty impressive. There is a bit of shine to the surface finish, more like “glitter” than gloss. There is definitely a texture to the surface as well. The strength and toughness is impressive.

One of my usual tests when trying out a new material is to print a Bency and see how hard it is to break off the smoke stack. I’ve been unable to break the smoke stack from any of the Priline benchy’s printed with this material. So if you have a part with smaller features that need to be built along the Z axis, printing with this material will give much more strength than had you printed with PLA or ABS.

Conclusion

After using all these materials, I would have to say that if cost is a big factor, and you just need a strong/tough material – the Priline seems to be a very good choice. Parts seem as durable, and cost a fraction of the price.

For the absolute best quality and lights-out reliability, nothing beats the Onyx Material if printed on a Markforged printer. Basically, if you can afford the premium cost to print in Onyx, you can likely also afford to use Markforged hardware, which I would recommend if you’re printing high-end end-use parts.