OpenExposer, The DIY SLA Printer


Precisely applied ultraviolet light is an amazing thing. You can expose PCBs, print 3D objects, and even make a laser light show. Over on the Projects site, [Mario] is building a machine that does all of these things. It’s called the OpenExposer, and even if it doesn’t win the Hackaday Prize, it’s a great example of how far you can go with some salvaged electronics and a 3D printer.

The basic plan of the OpenExposer is a 3D printer with a small slit cut into the bed, and a build platform that moves in the Z axis. The bed contains a small UV laser and a polygon mirror ripped from a dead tree laser printer. By moving the bed in the Y direction, [Mario] shoot his laser anywhere on an XY plane. Put a tank filled with UV curing resin on the bed, and he has an SLA printer. Put a mounting bracket on the bed, and double-sided PCBs are a cinch.

The frame is made of 3D printed parts and standard RepRap rods, with the only hard to source component being the polygonal mirror. These can be sourced from scrounged laser printers, but there’s probably some company in China that will sell them bulk. The age of cheap SLA printers is dawning, friends. Video below, github here.

25 thoughts on “OpenExposer, The DIY SLA Printer

  1. Whenever I’ve seen projects that use a laser to scan across to expose a PCB the problem has been that you either need a very powerful laser or it takes a very long time. I can imagine the same might be the case for SLA printing too.

        1. Perhaps you mean beam quality? Coherence has nothing to do with focusing optics unless you’re really worried about preserving the wavefront quality in applications where phase stability is very important (i.e. fringe contrast for interferometric applications, holograms, etc.. )

          Diodes tend to have poor mode quality because the output beam isn’t symmetrical, and usually highly divergent. On top of that, the optics that come with these crappy little diodes are usually low quality (plastic) and not well matched to the NA of the beam divergence. In short, they’re not designed for any application which requires any of the ‘usual’ desirable qualities in a coherent light source..

    1. Ben Heck did a video on how to make PCBs by painting them, etching the paint with the laser, and then using a conventional PCB etching process to finish it. At Texas A&M, they did something similar for “rapid prototyping” PCBs, though I have to say that their process for making vias is anything but stellar….

    1. Most printed objects are hollow or contain very little volume. A gallon of water is approx 8lbs or 3.6kg. Given that most filament is sold at around $40 for 1kg, we’re talking $180/3.6kg or $50/lb of resin. – Not a heavy premium from filament-based printers.

    1. Is it the kind driven by a flat brushless motor? If it’s on the board then the driver chip is likely near by. Read it’s number and find it’s data sheet and that will tell you. Of course this depends on a lot of ifs, I’m not sure if your mirror is even on a board.

    1. It would make the software more complex, because you’d have to compensate for the acceleration/deceleration curves at the ends of the galvo’s swing (cf. the patent for the RTI displays used in the Nintendo Virtual Boy).

  2. Hi, last time I tinkered with one of these (Apple printer), they needed +8V.
    A lot of these also have outputs for position and motor phase which can be used for real time feedback.

    One big problem with the optics mentioned earlier can be overcome if the correct optics (ie glass) are used, plastics and UV just don’t get along.
    A big improvement could be to use multiple beams on different mirror facets combining at the end into one large but somewhat focussed beam, using beam shaping via cutoff slits and removing all but the last optical components also helps.

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