3D Printing Forum

I had some really interesting experiences with XT-CF20 lately.
We are testing some new hard nozzle concepts at the University, it is part of a student project, and we used the XT-CF20 as a reference material.

After some initial testing with a normal model I went ahead and decided to design a "nozzle killer" model.
This model however had the opposite effect, it only caused about 10% of the wear that the normal model caused (!)

It appears like the wear the XT-CF20 causes comes from when the nozzle is changing direction rather than from the shoulder of the nozzle scraping along already printed surfaces.
The length of the carbon fibers might play a role here.
Here is how the fibers look when printed at 0.05 layers with a 0.4 nozzle at 50 mm/s
The fibers appears to be about 5 micrometer in diameter and 50-100 micrometers long.

Next up is to test print "nozzle killer V2"

Does anyone know what nozzle material Markforged is using on their printers for the carbon fiber filament?

I usually print at 40 mm/sec with ColorFabb PLA/PHA

Did you have to tweak the flow any?

I made this thing last year, lasercut the wood on my laser, and printed the handles in CF20 on my E3D V4. The paddle itself was modeled after an old Joola model which I had when I was a kid. Turned out pretty well, the photo shows the handles after sanding and a coat of lacquer. The thing I like most about the CF20 is how well you can sand it. If you're doing stuff which has big flat surfaces the finish is really amazing.

Superb

the print I did, a phone case, with XT-CF20 was pretty amazing! That surface looks and feels real impressive! The best phone case I made so far. All the others would split along the horizontal lines, like flex and woodfill.
Settings:
layer height: 0.16
speed: 30 mm/s
temp: 250
bed: 70
no retractions
no fan
printed on the UMO-HB with normal brass nozzle. I had a few meters of filament as demo, so I guessed that would not ruin my nozzle instantly...
Having no retraction was a precaution for a constant flow of the material, as the strings are really easy to remove afterwards, and to prevent the heat creating up. Do this also with the metal filaments (brass, bronze, copper).

Good information to know, I have been trying to get some Cura-settings info from ColorFabb and didn't get much that was helpful.

You didn't have to mess with flow at all?

I am a bit surprised at 30 mm/sec since others indicated it had to be faster.

You've given me a good baseline of what to try. Did you use glue stick or just glass?

flow was 100%, for the metal filled filaments I use a 105%.
I remember I had some blue tape on the glass (and heated bed), because the touch surface is small, only a few lines wide. Added a little brim to help there, 5 lines, which are also helpful for the leveling at the start. Hardly do any bed leveling, just add a few brim lines and turn the bed screws, if necessary.
A lot of the settings depend on the shape of your model, so going slow here and turning of retraction made a nice even surface.

What's your take on the strength of XT-CF20? I know they printed a bike, but other tests I have seen seems to indicate that it isn't that strong when compared to other filaments. So I haven't been able to understand if this filament really is strong or if it just has a nice look and some other improvements when printing certain type of models.

The one who printed the bike indicated that you should be using a .8 nozzle for strength.

We have done some tests, like printing the torque wrench in XC-CF20 and comparing the torque to pure XT.
It then appears that the XT-CF20 has a higher flexural modulus (is more stiff), just like the data sheet says.

We have not tested the tensile/flexural strength (how much load it can take before it breaks).
The data sheets suggests it is not stronger than pure XT though, which makes sense because the carbon fibers are very short and are thereby only glued to each other by the plastic, not entangled with other fibers.

Another experience I have with filled plastics is that many of them suffer from creeping (they permanently deform when kept under load). This makes them unsuitable for designs where they are under a constant high load strong enough for the construction to bend.

XT-CF20 is popular for manufacturing for example chassis for drones, where high flexural modulus maker sense, but I think most users use it for the looks.

One thing a friend mentioned for this filament and r/c is that it can block signals! I didn't know that

Thanks for sharing your findings so far. My main use case would be using CF-20 for playing with R/C stuff. I didn't really expect the carbon fibers to produce a lot of additional strength since, as you mention, it only contains small fibers. I need to put this filament on my to-do list to try once i'm up and running

nilrog wrote: My main use case would be using CF-20 for playing with R/C stuff.

I am not convinced about that... I don't really trust it is strong enough for my R/C applications (in the sense not much stronger than other materials), so I am using regular PLA for prototyping and mill 'real' CF plate when I am happy with the result...

But yes, you can't do 3D shapes with CF plates

I wouldn't expect it to be strong enough to build a big car that you race hard in terrain. For that I don't think there is anything available for consumer 3D-printing yet. But some smaller models, and prototypes, that are more just for fun I hope can be done this way.

Yes...

I do have a couple of 3D printed parts on the 1:5 scale car, but no critical pieces (cable holders, ...) and that's fine.
On the 1:10th I printed some spares (in XT), they do brake, but the injection-molded original parts are breaking as well

For things like spacers etc, it does the job...

XT-CF20 Vs. Carbon