Sunday, July 06, 2014

Homebrew stereolithographic 3D printer

I've been interested in hobbyist 3D printers for quite a while. A friend of mine, Jeff Keegan has an exquisite blog about his several-year hobby of building RepRap-style printers. He has donated a printer to the Boston Museum of Science. I took a stab at starting a RepRap-style printer years ago, but my level of dedication was not equal to the task.

A RepRap-style printer (technically, a fused-deposition-modeling printer) works by squeezing molten plastic out of a hot nozzle onto the workpiece, where the plastic cools, forming the next vertical layer. One FDM printer can create some of the parts for another FDM printer, or to replace its own parts when they get worn. This was the idea behind the RepRap project, that partially self-reproducing printers could be very cheap.

Stereolithograhic 3D printers operate on a different principle, using ultraviolet light to cure resin. The video above illustrates this process.

The past few weeks I have been spending way too much time trying to figure out how to build a stereolithographic printer of my own. I looked at a lot of things other people have done and started doodling some ideas. A few times I made or purchased parts for a particular approach and later realized that it wouldn't work for some reason. But after a lot of tinkering, I finally produced the octahedron on the right.

My printer is pretty crude and is due for a lot of improvements in the days ahead. I had ordered a stepper motor controller board that didn't work, so I needed to manually rotate the threaded rod that lowers the workpiece into the resin bath.

Hopefully this picture isn't too confusing. A lot of this is stuff from the hardware store: a bucket, a lot of plywood, nuts and bolts, a piece of aluminum screen, a threaded rod, two straight rods. That black shape at the top held in place with a bungee cord is a pretty standard conference-room projector. When the thing is printing, the projector aims down into the bucket, which holds a quantity of resin floating on a much larger quantity of salt water. The ultraviolet light from the pattern projected onto the resin cures it in a particular shape, forming one layer of the product, and then the threaded rot rotates, moving the product down by one layer-height.

Currently I'm using a layer-height of 1/40th of an inch, which turns out to be quite visible to the naked eye, so I want to go down to something more like 1/100th of an inch.

I plan to post plans and software on Github and Instructables to enable anybody to build one of these printers for just a few hundred dollars. Most of the cost ($350) is the projector. I'd like to do the RepRap thing of using lots of pieces made by an identical printer, which would involve some redesign.


Jeff Keegan said...


(not to correct you but I don't want to take any more credit than I deserve - I've only made one printer for the Museum of Science - I gave it to them without an extruder for 3 weeks, took it back to finish it, and gave it back to them a while later - now it's on permanent display)

.25mm layer height is pretty typical for FDM/FFM, but you should be able to go way lower than that with a setup like this, at least if I remember what I've heard right.

Can't wait to see it! Keep up the good work!

--Jeff Keegan

Jeff Keegan said...

(I have however printed lots of RepRaps.. I printed and assembled my first mostly from a Makerbot Cupcake, printed one from my first RepRap for my brother that he has assembled and working, printed and assembled one for the Museum of Science from my first RepRap, printed one for a coworker Joe Werther from the Museum of Science's RepRap before giving it to them, and printed and assembled my own second RepRap from my first RepRap).

John Locke said...

Appreciated work best video for any viewers here i should recommend one of the best Ink and Toner Cartridges for all compatible and genuine printers.

George Morgan said...

So far, the Fused Filament Fabrication (FFF) and Fused Deposition Modeling (FDM) are the most popular and commonly used 3D printing technologies because of its cheap printer and materials used compared to the other methods. Also, it has many sources and filament sourcing is accessible. One 3D printing supplier that I recommend is