I’m starting to get the feeling that composites might not be such a good idea in a 3D printer, as they are stiff, but break more easily than the pure polymers. Have you been having any luck with them?
https://www.youtube.com/watch?v=7HDG7Ju9YOI
See this seemingly confirms my belief that the carbon fiber filled filament is a huge fad, and doesn’t have any practical uses.
Is their any glass filled filaments using the micro glass balls? I know it is common in plastic modeling and machinable plastics to increase melting points and rigidity. I don’t know much of advantage of carbon filled fullerenes as it is chopped so not like a full carbon composite?
One of my favorite filaments is BambooFill from ColorFab. It needs to be printed fast at 50 mm/s minimum but it prints really nice and does not need to be very hot. While not as flexible as pure plastic filaments it is not so stiff that it breaks… so far. I’ve got some very nice prints out of it.
To use fibers one needs to have a reason and a plan. I have done a lot of surfboard repair and made a composite bike frame, the benefits of the material are the surface area or curvature transferring stress. Much of the strength is in the resin. the difference in strength and material qualities of a none woven bundle of fiberglass versus a woven cloth versus a thick mat is enormous. In individual strands with significant material between, its just not going to do what one expects from a composite fiber product. Different physical arrangement limiting all the benefits of tightly woven fibers usually encased in a hard resin.
Closest thing I have done to a layered carbon fiber filament is hand wrap the gussets of a bike frame with carbon fiber strands using tension compression to make a fairly good tubing connection. wrapping it like that is sort of like a printers layers, except I was leaning into it to make it super tight on the frame in a bike frame jig and was applying lots of resin to fully saturate and bond all the fibers. Its a nice custom frame 
Edit: almost forgot working in a composite boat yard long time ago helping repair diveboats I worked on. Seen a lot of use of composites and also a huge amount of damage from various forms of long term stress and force damage from impacts. I just do not see how the normal benefits of composite fibers work with the typical additive process, not that they can’t, people are clever. But right now off the spool through a normal printer, its just gold plating on a hubcap assuming one can see it through the print somehow. Also a handy way to unzip a print and deconstruct it, same as used in Ethernet cable to pull on an strip the jacketing.
With additive printing I could see layers not fully mixing with previous layers since previous layer has cooled. So adding fiber or glass will not add full properties like injection molding.
Could doing post print oven heat treating make layers bond more fully. This would be hard to keep structures dimensions. Mabe well printing using heated bed and heated enclosure could keep allow better layer intermix.
Hmm I’m curious on your take of Nylon filled with CF. I think you need a really small fiber size to get good quality. The print I saw off of a MarkForged with Onyx was impressive, but not sure about strength
@Mike_Kelly_Mike_Make , what makes carbon fiber strong is the fibers. If you chop them up to be infinitely small in order to fit through a nozzle…they lose their purpose.
print at high enclosure pressure, whatever compresses 3mm filament down to 1.75mm… slow return to ambient pressure while annealing down from enclosure print temp. I wonder what would happen? Dense heavy strong prints or expanded cracked horrormess?
Apparently, a company is doing what I would think would be the ideal use case: “Markforged launched the first and only affordable 3D desktop printer that embeds continuous fiber into printed carbon and nylon for an end-use composite part” – no chopped fibers. Continuous carbon fiber. I’d love to get a sample part from them.
Only issue I see with continuous fiber is how to get inter layer mix. Layers are week point in additive printing.
@ThantiK Well there’s multiple parts to a 3D printed part that’s strong. the first and most important to improve upon is layer bond strength. Nylon for example has 95% strength in the layer bonding.
The next is rigidity. Nylon is inherently flexible and not very rigid, once you add CF the nylon gains some rigidity and makes it much more useful.
Short fibers help with surface finish. The Onyx part I saw was very pretty and looked like a normal 3D print, unlike other CF prints I’ve seen that tended to look more like a sand paper print.
You are correct that to get the best strength from a print you need to use long, continuous, fibers like on the Markforged. But you can improve strength characteristics by filling the right materials.
We printed some CF filled Nylon at work and it was insanely strong (not onyx) Granted this was with a .8 nozzle so some strength may have come from that. It still has some flex but damn if I couldn’t get it to snap by hand.
@ThantiK CF filled filament are really good but not as they are offered. If you check scientific articles even a CF nano-tubes dispersed in Epoxy resigns add no more than 20% strength which is hard to be detected within our usage adding also worse layer adhesion means no more strength overall.
The important point come from the surface and compression strength of such composites. This composite is extremely useful for integrating as support parts within composites as the rough surface create really good adhesion with Epoxy and create very good bonding without additional treatment. For example pure PETG is very hard to be bonded from Epoxy CF filled is superb. Also filled parts are lighter than the pure ones. So as integrated composite support this CF filled PETG is really good.
What’s the case then when someone else (your employer) bought it and you’re just using it? Is that still confirmation bias?
Hardly. Do you have any idea how expensive stratasys material is? this stuff is peanuts comparatively. There is actually benefit to CF filled nylons and I can throw it on our instrom and hardness tester once I get some base nylon to compare it to.
@ThantiK btw, i’ll get a sample printer from Markforged this week. Only borrowed, though…
Nylon already has 95% strength in the Z relative to Y, which is very good. You will increase hardness while reducing the plastic region of the material, but as Nylon is almost too flexible to be useful for structural parts it really needs the CF to bring it to a useful point. It’s a very useful material if you need things that have good Z strength with minimal deflection.
Not sure why you’re so opinionated about this if you haven’t actually used it.
@Thomas_Sanladerer , The Markforged is the only CF printer that I’m aware of that should have a benefit to having embedded carbon fiber, simply based on the way that they do it.
Also, I know the people working on it - but I’m still not sure if I’m allowed to say anything.
MF parts are good under strain along the fibers but don’t do well under torsion or strain between layers. The real downside of the MK1 was that the fiber strand length needed to be very long (cutter through bowden to nozzle). By putting the cutter on the carriage for the MK2 you can get a lot shorter strand length so you can get fibers in tighter areas. With pure Nylon you need a LOT of CF to make the part rigid/strong enough, but with their new Onyx media you get a lot more rigidity without needing as much CF strand.
Also their CF Strands are known to crack and the spool which is oh so much fun to fix.
I think laying fiber into the filament at the nozzle using a separate feed into the side and a cutter is a better path. I have done a bit of soft goods sewing, taken fabric and fiber technology course in college, industrial CNC looms, talk about well designed engineering! Taking a bunch of different experience and interests into account… I would suggest a different system.
A hole at angle in side of nozzle that allows fiber to be inserted for desired length and cut precisely. Separate fiber feeding extruder pushes fiber into filament where adhesion into the layer takes care of pulling the last bit after the cut into the layer. A servo like one for a bed probe cuts the fiber when needed.
Keeping a fiber one wants tensile strength from out of the filament production allows both to be as appropriate to the design needs as possible. Filament is disappointing enough at times with the various issues one can encounter, not sure trying to make it do everything and bring you an omelet in bed is really the best route.
For bonding composites to the surface as others mentioned, small strands and a hairy surface are great! perfect to wrap and epoxy. I think in the future Carbon Filament reviews should take into account the end use of the filament in the fiber. acting as a structural support is different than a bonding material and texture for further manufacturing methods.