(Originally posted on Brace.design)
It's been a few months since I've dabbled with forged carbon fiber. So, I've had a fair amount of time to think about how I did it previously, and what I can do to improve it. I've also since come up with several more questions I want answered about it and what I can do with it.
The first time through was a success, but with several large drawbacks. The biggest of which was that the mold was not reusable after forging, and removing it from said mold was a process and a half in itself. (Breaking things should be easy, right?)
That is the biggest hurdle to overcome with test 2, so here's the plan:
Last time I was relying on 3D printed material to create the mold. While I won't completely disregard this method in the future (it could be useful for one offs) I'm not considering this an industrially sound way of forging carbon fiber. Another beef that I have with doing it that way was I wasn't entirely confident that my carbon fiber density was as high as it should be, or that I was applying the recommended 1400-1600 or so psi to the mold.
This time, I will be using a solid aluminum enclosure to forge the fiber, with a lot less extra fluff as before. What I'll do is take a 2 inch ID tube and and 2 inch OD rod and stuff one into the other. This way I'm more confident in my pressure range, and it will work better to study fiber density in the finished forging.
The first step was to make sure that the rod and tube fit nicely and could still be removed after use. I could just press one into the other just fine as is (it's soft squishy aluminum after all), but reusable is what we're going for. So I took some time to sand and polish the two so that they could slide in and out, while still maintaining a decent seal to keep the forging in.
One problem is that stock tube and bar stock are usually not perfectly round, so it took some time sanding down the high spots. I try and avoid lathes whenever possible (and I don't have easy access to one), so I did it all by hand.
I'm really happy with the way it turned out, and you can see in this clip how close a tolerance the two are; air pressure actually holds up the aluminum rod and slows its descent! (When it's not sitting on anything it falls straight through)
Now it's time to put this thing to work and forge some carbon fiber!
I lubed up and filled the cylinder up to the top with loosely packed, epoxy whetted carbon fiber strands so that I could derive some sort of compression value when I was finished. This all was then put in a small shop press so I could ram it home. This time I was able to generate the 1200-1500psi that Lamborghini and Callaway recommend for their forgings.
I did get some seepage out the bottom, so I may need to add a small flange and retaining disk onto the bottom to prevent that, but it wasn't that bad really. Removing the forging out of the cylinder was a little tricky. I ended up having to trim all the excess carbon fiber off around the edge and pushing the aluminum rod all the way through to get the newly formed "puck" out.
Now it was just time to clean it up into something presentable. I wet sanded it by hand to a reasonable finish, and it looks great! This time I feel like I really got a correct forged carbon fiber finish, with the swirling and marble like look that it typically has. Next up on the agenda I will try to machine this puck and see how it handles in a mill, which presents it's own hurdles.
Thanks for reading, and stay tuned!
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