The Oak Ridge team has a lot of capabilities in materials and processes to help in formulating the right type of materials with carbon fibers. Last year, the lab established a carbon fiber composites consortium. Since carbon fiber composites made out of autoclave with FDM represents a major shift, development will proceed in stages.
During the first 18 months or so, the partners will determine how to put milled, or chopped, carbon fiber in thermoplastics in an FDM process, and how to tailor the material's mechanical properties. The next stage will extend to the three-year mark and perhaps beyond. This will focus on laying down continuous carbon fiber on a center line of plastic wire, depositing that and growing it with the FDM process, and cutting it. "Since you can lay fiber in multiple directions, we'll take advantage of all the known statistical composite analysis tools, and integrate them into the FDM process," said DeGrange.
FDM is better suited to this project than other additive manufacturing techniques because it's one of the easiest to bring new materials to, especially multifunctional or filled materials, and for delivering them as a filament feedstock, said DeGrange. "It's easier to put carbon-loaded materials in a plastic line and maintain homogeneous repeatability than it would be to try this in a powder bed, for example."
Both methods have advantages, but when filling up a powder bed system with most plastics, the materials typically can't be recycled. The spectrum of thermoplastic materials that can be run in FDM is broader than with powder, and there's very little waste.
Jim, thanks for that very specific injection molding example. Since Stratasys and Oak Ridge are at the beginning of the 3D-produced carbon composites research project, they're still defining parameters and performance targets. In composite manufacturing, there are a lot of variables and everything's contextual.
Recalling a particularly high-volume job I once designed, being a fully-automated 2-cavity, injection molding operation which produced a thin-walled plastic cell-phone housing at a molding cycle time of about 20 seconds ,,,,, That's 6 parts/minute.
So the point raised about production molding cycle time vs FDM cycle time is a very valid point; and that 2 cavity example was a run-rate that I truly doubt any deposition process could ever match, (let alone, exceed).
But the tool cost of that set-up was around $280,000 as I recall, and the deposition process set-up is nearly zero by comparison; so we need to remember all of the variables in the equation for economy.
I applaud and eagerly watch the FDM experiments advance.
Since they're working on both materials and processes, like those researching non-3D assembly, the material will most likely not involve resins that need to be cured. Many of the attempts at automating carbon fiber composite production are either developing much faster-drying resins, or avoiding them entirely. Regarding increasing speed, well, that's the main point of this research.
A lot depends on how much, fast it can put material down. Unless very quick or only 1-3 units needed, it's going to be hard to beat using molds either either hand or machin layup.
Now with the mold making by machine/Cad, making a mold costs little inhouse leaving little start up costs in that technic.
Whether it needs an autoclave depends on the resin chosen mostly.
But even their the mold can be designed to be heated so spray fibered resin by hand or machine and be it's own autoclave taking little more room. It's how I normally handle faster curing. Since most curing produce their own heat just insulation could do with many resins.
The range of printed items from so many new materials including metals will change a lot of things but is likely too slow compared to well done mass production, at least for now.
Jim, considering all the hassles involved, not to mention costs, of producing carbon composites and all the R&D being pursued for faster, cheaper production methods, it boggles the mind that we could simply solve the problem by making them with FDM. But why not? This project is aiming not just dollars but some pretty creative and experienced brains at the problem. Maybe you're right: if we can solve this problem, then maybe FDM can be applied to a lot of other materials not considered before for AM techniques.
Really a fantastic concept, Ann. When I think back to the first days of rapid prototyping and remember wondering "who came up with the idea of solidifying liquid polymer with a laser?" Then, I look at this technology effort and am confident that it, too, will succeed as just one more example in our human journey of discovery. The explanation of the spindle-like carbon fibers being delivered via a filament brought a pretty clear image of intent, and I don't doubt they will eventually accomplish their goal. What a fantastic thought, really; perhaps we can eventually FDM virtually any material?
Yes, TJ, that's one of the biggest deals about this project. Autoclave ovens are big, expensive and slow. Getting rid of them in one way or another is one of the goals behind several different research projects on speeding up carbon composite production, including this one we reported on earlier this year: http://www.designnews.com/document.asp?doc_id=239474 "Out of autoclave" is to composite production a bit like "Open sesame" was for Aladdin trying to open the cave.
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