3D printers

A FlexMendel 3D printer, operated by open-source software on an Arduino digital controller.
A FlexMendel 3D printer, operated by open-source software on an Arduino digital controller.

I’ve been working with 3D printers lately. Built one, in fact, during a workshop at Open Source Classroom. The printer is designed so you can see all its working parts, and I’ve been heartened by student and faculty interest in it. They’re fascinated to see a digital file, which has no mass or shape or form, be fed into a machine along with some plastic filament, and out comes a solid object you can look and hold and experience.

There’s a lot to say about the social and industrial impact of 3D printing, but my favorite questions are the ones on how it works. Because this is actually very familiar technology to all of us. We see it every time we hit “Print” on a report or picture.

Explaining the 3d printer

I started out explaining it this way: “It’s basically the same as an old-style dot-matrix printer, with one extra axis and substituting hot plastic for an impact print head.” After a few blank looks, I realized that most students had never seen a dot-matrix printer. Only older professors, who got their start printing mainframe jobs on a big dot-matrix line printer, could visualize what I was talking about.

(Excuse me, I’ll just be over in the corner here, feeling really old.)

Fortunately everyone today has seen an ink-jet printer, and the only difference between an inkjet and a dot-matrix is the type of print head. Inkjet printers move an ink-squirter over the paper. It goes side-to-side (the “X” axis) and top-to-bottom (the “Y” axis) to deposit an image. The printer is controlled by a built-in controller circuit, translating the image on your computer. Simple, right?

Back-of-envelope sketch of a 3D printer. Most of it is actually pretty old-fashion tech.
Back-of-envelope sketch of a basic 3D printer. Most of it is actually pretty old-fashion tech.

Now suppose you added a third axis; “Up and down”. Straight up, off the paper. Call that the “Z” axis, so you have an X, Y, and Z axis. And replace the ink squirter with a device that squeezes out hot plastic. Now you can not only print a pattern, but you can build up layers; that’s a 3D printer.

Layers on layers

“Print” a plastic circle for your first layer, and then another one on top of it, and one on top of that. Keep it up for 300 layers and you have a cylinder 12cm long. Change the pattern a bit from one layer to the next, and you can make “arbitrarily complex” shapes. Some of them, impossible by conventional machining methods.

Combining old tech with something really new

You could have built a 3D printer in 1970; all the components already existed. Step motors (that turn in discreet steps, instead of just spinning round and round)? Check. Precision machined rods and oil-soaked bronze bushings? Check. Control circuitry? Yep.  Meltable plastic? Sure. Computers and machine control language?  Um…

An arduino processor with some extra modules connected. The future is here, and it's not all that expensive.
An Arduino processor with some extra modules connected. The future is here, and it’s actually pretty cheap.

OK, all that stuff existed, but the price would have been way out of reach. Your descriptor file would have been encoded in a punched paper tape, or on punch cards, or on huge reels of magnetic tape. Your computer would have been the size of a refrigerator. You would have had to hire an engineer to do the translations and programming.

Today, think open-source software and an off-the-shelf Arduino processor you can hold in your hand. You’re talking less than $200 for a control circuit that would have required a Pentagon (or Bruce Wayne) budget just 45 years ago.

Hobbyists are building printers out of recycled parts, and with economies of scale, there are many complete models available for under $500. That’s the low end of 3D printing, but the technology is bustin’ out all over. There are 3D printers the size of houses, ones that use liquid polymers and UV lasers, and electron-beam printers that compose objects out of charged alloy molecules. The SpaceX corporation prints their Dragon rocket engines, and just delivered a printer to the International Space Station. (I suppose that makes sense: if you need a new part for something, and you’re in orbit, it’s a bit hard to just “Add to cart” on Amazon.)

But the biggest impact of 3D printers may be in the Third World. More on that, later.

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