December 10, 2017

I’ve been passively playing with the idea of getting a resin 3D printer for the better part of the last year. Initially, I was considering picking up one of the Wanhao Duplicator 7 machines, partly because that machine could be had for as little as $400. However, I heard enough troubling reviews about the machine to wave me off. Apparently, the Duplicator 7 uses what is essentially an LCD screen with a bright UV backlight to cure resin in the vat as the machine works. From what I’ve read, the LCDs are not really prepared to deal with the effects of prolonged UV exposure, and start to break down over time. Compounding that is the fact that replacement parts can apparently be fairly tricky to track down.

Enter Peopoly. I watched their Kickstarter with the typical cynicism I reserve for such endeavors and did not pledge, but this is one of those projects that beat the odds and became more than vaporware – much more, apparently. Every so often I’d see a post go up on r/3DPrinting with some ludicrously high-resolution part that was apparently produced by this unlikely machine, which would end up with me doing more investigation into whether or not it was a credible option. I joined their Facebook group so I could spectate a bit, which only ended up fueling my interest in the machine much more substantially once I saw the quality of prints people were consistently producing.

Then Black Friday came. I didn’t actually see much in the way of promotional deals on Peopoly’s site, but had the machine at a discounted cost of $1,179.00. Not the huge incentive I would have liked, but it was enough to make me pull the trigger on the machine. I also purchased some resin (because, note, the machine doesn’t come with any from MatterHackers. What the hell?) and a spare vat, which is basically a container with a rubber layer on the bottom that the parts build off of.

The machine arrived about a week ago, and I spent an evening getting it built and calibrated. The process took probably about 5 hours in total, and I filmed my way through it, though Twitch was kind enough to selectively mute or delete some parts of my video because I had the nerve to listen to background music as I worked. The instructions were decent – though not quite enough to save me from building a few parts wrong as I went, which then had to be deconstructed and fixed once I realized my error(s). Still, nothing too tricky about the process. Just screw the frame together, plug the various electrical parts together with clearly labeled wires, offer up the necessary blood sacrifice to ensure the machine is properly leveled and calibrated, attach the slick black casing on the outside of the machine, and off you go. I’m joking, but the calibration process looks like it could use some work. Practical Printing on Youtube has a very good video tutorial on the process that I was able to follow that basically got me up and running on the first try, though I have a bit of cringe-by-proxy at the faux enthusiasm and constant use/abuse of “aloha” in every video. Whatever, he’s clear and concise about what needs to be done, and it’s not like my own videos are any less awkward.

For a while, we did a pretty brisk business on our Etsy Shop selling cold cast copies of our Immortan Joe medals. The unfortunate reality with rubber molds is that over time they will start to degrade and wear out, leaving you to re-make them periodically. I managed to somehow lose the copies of the original medals, which meant that if I wanted to make new molds, I’d have to re-print the medals. I adore my Makergear M2 and it has basically been my workhorse printer for these past three years. Even so, it would have been super annoying to try and re-finish those prints to remove the print lines from a whole new set of medal masters. It seemed like a good first use case for the Moai, so I set about getting everything printed out of the new resin monster.

The approach to setting up resin prints is completely alien to me after years of doing FDM printing. The layers print in reverse, for one thing – the parts get pulled up out of a vat upside-down, rather than built bottom-up like on a normal filament printer. The laser hits the resin where it meets a layer of PDMS rubber on the bottom of the vat. This hardens the resin via exposure to the UV wavelength of the laser, and it sticks to both the rubber and the build plate (or subsequent printed layers) above it.

After each layer is complete, the entire vat dips down gently to one side in a wave/rocking action to peel the layer off the PDMS rubber, and the build plate moves up by infinitesimally small amounts as it builds the piece. You need the piece to be properly anchored to the build platform by enough supports to keep it from pulling apart during this peeling action.

The parts tend to be tilted up at an angle when you print with these machines. Part of that is simply because if you were to try and print the model with the flat side down, you’d be peeling a lot of material per layer off the bed, which can start to ruin the PDMS rubber layer. Moreover, printing it at an angle does a nice job of hiding what little evidence of print lines this method leaves behind.

Immortan Joe’s eagle badge was the first thing I printed after getting everything calibrated, and I think it’s safe to say it came out really, really nicely.

As amazing as the Moai prints come out, they still require some post-processing work. You have to scrub down the parts with 99% isopropyl alcohol to remove some of the extra resin that’s on the part surface, as it forms a viscous layer that would otherwise obscure detail. After you wash and rinse the parts down, you essentially need to give them a final ‘bake’ under a UV light source. I’ve opted for a pair of 36-Watt UV nail gel dryers which I position back-to-back to make a sort of ‘chamber’ for the parts to cure in. It seems to work perfectly, and the heat generated by the setup inside the chamber actually seems to help cure the parts, as well.

After this initial print, I actually decided to revisit the model and push my luck. The real medal on Immortan Joe’s armor has text in the oval area that reads “Easyriders”, but I left it off my initial model, as even Shapeways refused to print details that small. I added the text and other necessary small details, including a bit of a rippled texture behind the text to simulate the enamel:

The Moai printed these extra details without even a hint of difficulty, which I still find a little ridiculous. Here’s the version with text plus a coat of primer, to hopefully make things easier to see:

Encouraged by these results, I reprinted all of the master medal files in resin on the Moai. These were all printed at 50 micron layer height. I can push my Makergear M2 to also print at 50 micron layer heights with its filament, so I decided to print a set on that machine as well – something of a head-to-head competition. The Moai wins handily.

As impressed as I am with this whole thing, the resin printer is not without its downsides. Resin is substantially more expensive than filament – these parts cost 2 to 3 times what they’d be on the FDM printer. It is also more toxic and obnoxious to deal with, and somewhat limited in size. Still, the Moai does its job extremely well, and I’d strongly recommend it to anyone considering this type of printer.