Tag Archives: korean barbeque

B-(A+C): Booleans and We The Builders

3D printing luminary Todd Blatt is of late heading up his second bit of crowdsourced Americana with his We The Builders project, Ben Franklinstein.

I missed out on the first pass at this with George Crowdsourcington, and since Todd overtipped our server for his share of Korean Barbecue the last time we met IRL, jumping in to help out with Ben Franklinstein seemed like The Right Thing To Do.

Here’s how this works. Everyone who wants to be involved downloads a piece of a scanned Ben Franklin bust. We print it, scrawl the piece’s coordinates on an inward-facing side, and ship it to Todd and others who assemble all the pieces somewhere in Baltimore.

The result’s a nifty pastiche of plastics in the form of a Founder. A quilt of quadrilaterals, if you will. Here’s what George Crowdsourcington looks like, all assembled.

I’ve printed two blocks for the latest project. My gold block is plain Jane, but I decided to do a little shenmeshenme on the blue one.

blocks

The first order of business was carving out a hollow inside the block. One’s first thought is to make a perfectly cubical void, but that’ll cause the roof to sag when printed on an FDM printer. So a peaked void it is, tapering to a single vertex at the top.

cut

Maya models surfaces, not solids, so subtracting the void (A) from the main geometry (B) isn’t a valid operation; B minus A equals B in this case. Printing B will get you a solid block, which is not what We The Builders want in this case.

The solution is to model a thin snorkel (C) connecting the void to the outside. This snorkel is mathematically legit, but too small for the printer’s resolution. The end result will be a printable void with no visible snorkel. We’re doing B-(A+C) here. Woo! Booleans.

You can grab the model here if you’d like to inspect this snorkel for your own mean self.

Midway through the print we do the old pause-the-print-and-drop-an-object-in-the-void trick, in this case a golden zheng. You can’t see the zheng from the outside of the printed model, but it does rattle a bit.

zheng

And then it’s a simple matter of finishing the print, boxing it up, and shipping it off to Todd and company.

The crowdsourcing phase of We the Builders is scheduled to wrap up in mid-September, and they’ve still got a few blocks to go. It’s free and a lot of fun, so go ahead and add your 3D printed stamp to this creative endeavor.