Wednesday, July 09, 2014

Cleaning up the SLA printer design

The stereolithographic printer described in my last post works, but it has a lot of room for improvement. Two obvious improvements are to use a stepper motor to raise and lower the build platform, allowing for automated operation, and to accept standard input files such as the STL file format.

In this post, I'd like to look at improvements in the overall mechanical design, specifically intended to make this printer easy for other people to build. I envision this as a printer that could be easily and affordably built by an after-school club, at a price of less than $600. The projector I used cost me $350 and I'll assume that's the same price for others. Likewise I expect others would pay about $75 for a couple of bottles of UV-cured resin. That leaves $75 for everything else. You have a stepper motor, a stepper control board, and a Raspberry Pi. I have a little wiggle room left for laser-cut plywood, and a 5-gallon bucket from Home Depot. I get my laser-cutting done at danger!awesome in Cambridge, MA. The bucket is bright orange, and that's the color I've used in this design, where the plywood is yellow and green (the green pieces having gear teeth that mesh). The pale blue stick-things are 1/4-20 threaded rods, cheaply available at Home Depot. The brighter blue thing is the stepper motor. The three green gears surrounding the threaded rods have captive nuts, allowing the stepper to raise and lower the threaded rods in lock-step. I'm kind of pleased with this design and I think this is what I'd like to show at Maker Faire NYC this year.

Looking down into the bucket, we can see one more circular piece of plywood which is the build platform. When we raise the three threaded rods high enough, the build platform comes up out of the bucket, which holds a layer of resin floating atop a salt water bath (a trick I borrowed from the Peachy Printer). And in fact, you could use this setup with a Peachy Printer rather than a projector, and you'd save money by doing so.

These gorgeous pictures are courtesy of It's a pretty wonderful thing if you're doing 3D design. One last picture, showing the projector bouncing light off the mirror to illuminate the resin.

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