Running a small product design and 3D printing business, shookideas.com, I receive questions about carbon fiber filament almost every week.
So then, what does carbon fiber 3D printing filament really have to offer to the desktop 3D printing consumer? When I’m analyzing new materials to stock in our shop’s inventory, I ask a few basic questions.
What is the filament made out of? Most carbon fiber filaments are just PLA or another 3D printing plastic mixed with shredded bits of carbon fiber. Compared to the carbon fiber you see on a Ferrari or Porsche, we’re talking a completely different combination of materials. Those parts are high-performance components manufactured through the process of molding. This requires machining a tool, laying out the carbon fiber fabric, applying an epoxy resin and then curing the part in a high-pressure, high-heat environment.
So, aside from both materials containing little fibers made out of carbon, they are worlds apart in terms of chemistry and processing. To make matters worse, one of the main reasons why I choose other materials over PLA, the base polymer in the filament, is because it is brittle and prone to cracking. Once carbon fiber is added into the mix, the material becomes even more brittle. Things aren’t looking good so far.
Visually, how do the parts look after they’ve been 3D printed? This is the area where carbon fiber filament does best. In my opinion, the parts are aesthetically pleasing with a matte black finish. PLA and most other materials have a glossy shine to them, so this is a differentiating feature. But, I’m a self-proclaimed 3D printing nerd; and when I try to imagine this from a general public perspective, once again, things aren’t looking good.
Unfortunately, the parts don’t look anything like the beauty of molded carbon fiber. Molded carbon fiber parts have an iconic “weave” pattern that you can see from the carbon fabric frozen in suspended animation beneath the epoxy resin. So, if you were expecting people to recognize your parts immediately as “carbon fiber,” think again. You’ll have to tell them about it.
Next, what are the “printed” part properties? In other words, how could I use this material for an application in everyday life? I'm usually able to answer this question by simply searching on Google for products that already use the material in mass manufacturing. Once again, this is an issue because everything that comes up relating to the term “carbon fiber” points to applications I wouldn’t dare with fused deposition modeling (FDM) 3D printing. Would a normal hobbyist or small-business operator recognize this before actually buying the material?
Admittedly, I bought carbon fiber filament before I started to understand these issues. But, in almost every case I’ve seen, I’ve found there are huge differences in tensile strength, impact strength, durability and much more when comparing to the manufacturing methods we’re used to.
In general, desktop extrusion 3D printers make parts that are 30 percent to 40 percent weaker in tension than their injection-molded counterparts. I’m not aware of any specific data on this subject, but in the case of molded carbon fiber versus printed carbon fiber, I would guess that the strength difference is orders of magnitude less rather than a simple percentage. That’s a critical point of reference when I’m trying to engineer and test the parts I’m 3D printing.
Further reporting on issues not included in this article can be found here on Fabbaloo. Note: This article describes chopped carbon fiber filament, used most often with desktop 3D printers, and not industrial carbon fiber 3D printing technologies like those from Markforged, Impossible Objects and EnvisionTEC.