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  • Writer's pictureNed Patton

3D Printing - AKA Additive Manufacturing

I thought this week I would spend some time on a field that is up and coming and seems like it is going to rapidly take over a lot of other methods for making things – especially out of composites. I’m talking about the emergence of 3D printing – aka Additive Manufacturing. Just in the past few years, this technology has matured from the hobby shop level (think Lulzbot Taz – I had one) to large frame 3D printing machines, some of which are capable of printing metallic parts to high precision. 3D printing or Additive Manufacturing of composite material parts has become mainstream just in the last few years.

One of the first companies that made a big deal out of printing continuous composites was – according to Composites World – MarkForge with their Mark One printers. These were announced at the Solidworks World conference in 2014 to great fanfare. Then came a company called Arevo with a full 3 axis continuous fiber composite 3D printer that could print with continuous fibers along contours. Then there was Orbital Composites who worked with the Composites Technology Center in Stade, Germany and makes very large scale machines that can print continuous fiber composites void free. Even Oak Ridge National Labs has one of these machines.

But another company started printing continuous fiber composites in 2012 that needs to be mentioned – Continuous Composites in Coeur D’Alene Idaho. These folks have really perfected the art of printing continuous fiber composites in all three directions, and can even incorporate copper wire, nichrome wire, fiber optics, pretty much anything that is fibrous in nature. That’s why a pic that sort of advertises them is to the right above.

The materials that can get printed span a complete range from chopped fiber thermoplastic composites to full continuous fiber thermoset composites and everything in between. If the resin is a thermoplastic and the fiber is chopped, almost any 3D printer can handle that as long as the nozzle of the print head can accommodate the length of the fibers. And these printers tend to align the chopped fiber in the direction that the nozzle is printing, so you get an aligned fiber structure even with chopped fiber.

For continuous fiber composite printing, mostly it is done using the process shown to the right where the fiber is laid down from one spool and mixed with the thermoplastic feed wire in the print head itself. The fiber is fed in while the thermoplastic is melted around the fiber and laid down on the part. This creates a structure in 2D – essentially laying down the composite layer by layer – in essence mimicking how a part would be hand laid. The resins that can be used for this process are somewhat limited because the resin needs to harden very soon after it is laid down on the part or the fiber moves around and ruins the part.

That’s the way most of the continuous composite 3D printing happens. Continuous Composites, on the other hand, has developed a means of 3D printing continuous fiber composites using multiple spools of fiber ( shown to the left), and using both thermoplastic and thermoset resins on the same part. What they call their CF3D (Continuous Fiber 3D) process can print as many as 16 tows wide of 12k carbon tow using a thermosetting epoxy resin.

That’s 12,000 fibers per tow, and 16 tows wide, or 192,000 fibers at once. That’s a lot of fiber to be 3D printing at one time. That sort of laydown rate is what is catching the attention of aerospace manufacturers, auto manufacturers, even the Federal Government in the National Labs. The top center pic is an airfoil that was made by this process, and you can see that it has very complex shape. What isn’t quite so obvious is that this is a continuous fiber composite part.

Another example of continuous fiber 3D printed parts are the bicycle frame lug the pic to the right that connects what looks like the seat post to the top tube and the rear stays, and the parts that you see in the pics below that one.

One more thing of note in the pics here is not necessarily 3D printed composites, but it is 3D printed tooling for making hollow carbon/epoxy parts for the automotive and aerospace industries. There is a company that has created a 3D printed “sand” that has a water soluble binder that gets printed with the sand (which makes it a composite material now that I think about it) that can be easily washed out of the completed and cured part. This has also cut the cost for manufacturing of these very complex hollow shapes and removed the majority of the hand labor from making the molds.


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