Saturday, October 6, 2012

Printed Fins, Futures Base

Here's a project tangent: 3D printing fins.

When I first got this buggy plastic extruder a year and a half ago, I printed a couple tiny fins before the original motor began to fail. Just recently I pulled the contraption back out and fixed it up enough to print out some replacement/upgrade parts to make it much more reliable (the white gears in the picture). So now I'm back in the 3D printing game, with this extruder temporarily bolted onto the CNC router.

The quality with this setup is just good enough to start making mechanical parts for surfboard-related schemes I'm working on - but also good enough to play around with printing small fins.

I've got about 4.25" of vertical travel with this setup. So a fin with a half-inch deep Futures box base can only be about 3.75" tall. That's what you see here:

Anybody see the big problem with this fin? No - not the little crack at the trailing edge. Not the slightly textured surface. There's something wrong with the base. The base is almost perfect. But ...

it's backwards. That's right, I designed the base with the notches switched around. But it does fit nicely in the box, and only took a little touch up sanding work. So, yeah, fail, but success anyway.

I've only got this one early board with Futures boxes, and the box mount job itself is a bit funny. I mounted too shallow and sanded too much, so the boxes aren't as deep as they should be. That's why the base sticks up a bit here. The grub screw pins it down though, and the fit is tight, so it's secure.

Now, about 3D printing: the technology to print a surfboard has been here for a while. It's probably been done, though I haven't seen it. Maybe you have? Maybe secret prototypes are out there incubating, and we'll see the printed surfboard start-ups emerge soon.

What I'd like to see is some cheap, tall, RepRap-derived 3D printers built in garages, apartments, dorm rooms, able to print a 6' board overnight from maybe $50 worth of biodegradable - maybe even self-recyclable - plastic. It looks like that's possible today. Maybe a first step would be to build a printer with a 12"x4"x6" envelope, and print a board in sections.

Add that to my tangents list. The main focus now is on building a laser cutter, so I can develop more detailed cardboard core designs, and designing and printing parts for a servo-driven coelostat, for the SolarCNC project.


Gaspard said...

The printer uses plastic filament, right? I would have it deposit the material perpendicular, not paralel, to the surfboard. That way the layers don't suffer from shearing or peeling stresses caused by the water pressure when doing turns in the wave. Love your work by-the-way. Very inspiring.

Cantilever said...

I would bet money you can ride with that "backwards" fin and not feel the difference. I would be great to get it in the water and see how it holds up- @Gaspard has a good point about the layer orientation.
Great work, thanks for the post!

Helge Munk Jacobsen said...

Awesome! Could you make the CAD files available?

I have been searching elsewhere, but I can only find these two:
..but I guess I would have to add the base myself, and I have no clue how to do that.

Anonymous said...

Wow - my blog gets real comments! Sorry guys - I didn't see these right away.

@Gaspard - Yeah, different orientations should be tried. It's a pretty simple clean toolpath to print like I did, so the surface quality has a decent chance of coming out okay. But yeah it has the "grain" going in a weak way.

Probably the best potential here is to print fin cores that get hard-coated/glassed later, so the core doesn't need much strength, just good form.

@Cantilever - Still looking forward to trying that fin like that. I'm with you - I don't think it's going to be a problem. Or let's just say it will be the least of my problems.

@Helge - I've got a system for making fin STLs with different box bases (just Futures and Bahne for now.) Hopefully I'll get back to developing that a bit more so I can publish it. Or it might be neat to try make this work with the Thingiverse customizer.

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