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More Adventures in 3D Printing

The D&D boardgames come with plastic miniatures. They’re not especially nice, but neither is anything else out there.

So, I started playing the D&D boardgames with my kids. The games are pretty good (I initially bought them as a way of getting a buttload of materials for playing regular D&D, but that went nowhere).

But, my game designer brain won’t shut down… I had already toyed with the idea of a card-based RPG system, but couldn’t quite get it working. My (minor) frustrations with the D&D games gave me an idea. I’ll get to that in another post.

Anyway, in a nutshell, D&D boardgames with miniatures led me to think about custom miniatures which led me (back) to HeroForge which led my to think about 3D printing, and thus I discovered that SLA (stereolithography) printers have suddenly gotten a lot cheaper and by all signs are actually good.

So, I bought a Voxelab (or maybe Voxellab? — they can’t make up their minds) Polaris resin printer for about $160 plus tax, and a couple of 500mL bottles of resin for about $15 apiece.

This all arrived on News Year’s Eve. Woohoo! Champagne and 3D printing!

The printer didn’t come with any resin, and the instructions make reference to items not included: e.g. a container to dip prints in denatured alcohol, denatured alcohol, and a curing box. I made do with old jars, ordinary 70% alcohol (more on this later; a costly mistake I think), and paper napkins and the initial results were amazing.

Setup is amazingly easy. You basically:

  1. Place it somewhere level(ish)
  2. Plug it in
  3. Pull out resin tray
  4. Place a sheet of paper over the spot the resin tray occupied
  5. Loosen two screws on the print head, allowing it to move
  6. Run the print head down until the paper is flattened
  7. Setting this as ZERO
  8. Raise the print head
  9. Replace the tray
  10. Pour in some resin (word of warning: it’s really hard to tell how much transparent resin you’ve poured in).

This would have been quicker if the instructions weren’t in broken English and were decently organized and/or had an index. Even so, not bad at all.

The software is provided on a USB stick, which is big enough to serve as a file transfer device (this printer doesn’t do WiFi, so you save models (in *.fdb format) using the included Chitubox (free) software.

Chitubox is a semi-nice program. The buttons are all non-standard, tiny, nearly indistinguishable, and have no tooltips. So that’s nice.

My single biggest frustration was figuring out how to import the profile (on the USB stick) into Chitubox (once installed). Turns out there’s a video that more-or-less explains the process on the stick.

To print a 3D model (or several):

  1. Export models as OBJ files. (Ideally a model should be “water-tight” and clean, but it’s very forgiving.)
  2. Import one or more obj files into Chitubox.
  3. Scale, rotate, position the models to taste.
  4. Go to the supports tab and click Add All.
  5. Go back to the first tab and click Slice. This may take a while
  6. Drag the slice slider (not to be confused with the view slider) up-and-down to look at the cross sections and check they seem correct. (The view slider shows you a quickly calculated cross-section of your model, the slice slider shows you the actual rendered cross-section that will be used to print a layer.)
  7. Save the model (as FDG) to a memory stick.
  8. Put the stick in the printer.
  9. On the front panel pick your model (a correctly saved file should display your model; ignore weird Mac hidden files and such) and press Play.
It’s definitely worth scanning through the layers after slicing to sanity check before spending hours printing something that makes no sense. One annoying mistake I’ve made is making hollows with no place for the fluid to drain (or rather making them in the wrong place).

Printing

Here’s the printer in action. The curved thing is the print platform—a solid hunk of aluminum—and it is bathing in transparent resin (you can see bubbles in the resin towards the top-left). After each layer is exposed, the head is pulled up 5mm (this is adjustable) which draws more resin under the print, and then lowered 0.5mm above its previous exposure position, and so on.

Printing is slow (but it’s dictated by the height of the print, not the volume, so you can print a bunch of miniatures in parallel just as quickly as you can print one). It’s printing your model 0.5mm (?) at a time (with antialiased voxels!—or maybe just pixels) and each for each layer, the model is lowered to 0.5mm above the glass plate (at the bottom of the resin chamber), exposed, then raised to allow fluid to seep in. Lather, rinse, repeat.

Each layer is being printed by shining a UV lamp through an LCD displaying the bitmap cross-section for that layer (as seen in step 6, above). That’s it! (The printer displays the layer being printed on its color touch screen.) Mechanically, this is much simpler than an FDM printer, and the quality of the output is dictated by the resolution of the LCD screen and the quality of the resin.

The printer is quiet compared to FDM (still, a pretty loud fan) and it doesn’t cause noticeable vibration (it’s only moving the head up and down with a screw drive).

When it’s done, it beeps and raises the print clear of the resin basin.

  1. Rinse it in alcohol
  2. Pull it out of the alcohol and let the alcohol drain
  3. Leave it to cure somewhere well-ventilated

So, how good are the results?

Fresh out of the printer, transparent prints look amazing. This is all covered in liquid resin—goop Gwyneth Powell might be proud of—probably not. Below the toroid you can see the support platform (from which the model hangs during printing.

It’s hard for me not to be hyperbolic and create unreasonable expectations, given my previous frustrations with FDM (fusion deposit modeling, or “robot glue guns” as I call them), but here goes.

This is the first inexpensive 3d printer that I have found not to be disappointing.

This is the first 3d printer I have used that produced a good model the first time I used it. (And, no, it wasn’t the demo model that came with the USB stick.)

This is my first print, 36h after it emerged from the resin. It is perfect. (The support platform looks nicer than anything I’ve seen out of an FSM printer). If you pixel peep you can see “sedimentary” layers in the print surface, but this is not reflected by the surface feeling rough. The only blemishes are tiny nubs where the supports were broken off.

I compare this to the first time I saw printed output from a laser printer, or the first time I used a good color flatbed scanner, or the first time I captured video from a broadcast quality camera with a broadcast quality capture card. In terms of output quality, this shit has arrived.

In a nutshell, the output is smooth (wet, transparent output almost looks like glass, but it becomes cloudy as it cures) and the prints feel rigid but a little flexible. The way I describe it is “somewhere between plastic army men and lego”. Prints feel about as durable as a nice plastic manufactured item of the same form (perhaps slightly nicer than the plastic D&D miniatures that sent me off on this tangent).

I should add that the printer estimates the cost of each print based on the volume of resin to be used and the cost of the resin. So far, my models have “cost” less than $0.25. But they’ve all been quite small. (But wait to find out about other consumable costs…)

Flies in the ointment

New printing method, new failure modes. This print of my omnidude model mid-run looks great at first glance, but turns out to have a defect—partially visible here (most of the right leg is missing, as is the back of the base. I believe the cause is deposits on the PEP film blocking uniform exposure or possibly the a portion of the print base failing to adhere to the head.

Let me begin by saying that most of this is a result of user error. I couldn’t get pure isopropyl alcohol on New Year’s Eve at 10pm and I wanted to play with my toy!

Let’s start with nasty chemicals—the resin smells bad, and is viscous, sticky, slimy, hard to clean off, and probably bad for you. One bottle of resin arrived having leaked a bit inside its container. The prints—perhaps because I’m not using pure alcohol and/or don’t have a proper “curing box”—are slightly tacky for hours after printing. Nevertheless, my first print has lost almost all its tackiness 36h or so since printing.

Recovering unused resin using the provided paper filter is horrible, and cleaning the tray is painful. But then there’s some really gnarly issues…

First, my second print had some odd, minor flaws in it, which I ascribed to my modeling, but turned out to be much nastier.

Next, we had a power failure while a print was in progress and the printer lost track of where it was. I tried to recalibrate by just moving the print head down and fiddling (rather than draining all the resin and cleaning everything and recalibrating properly, and so on, but it didn’t work.

My weasel character was one of the two figures in progress when the power failed. (Shown here atop a quarter and an old two pound coin for scale—this thing is tiny.) It shed a few layers from the back of its tail, and there’s that small blemish on the front of his abdomen (which I don’t see with my eyes). I added some very fine detail to the eyes (an indentation on his right (cyborg) eye, and a pupil on his left eye. The latter isn’t visible.
This profile shows the flawed fail, several layers of which sloughed off at a touch.

My first print after the power outage and my dodgy recalibration was a disaster. The model fell from its supports and became a nasty blob, lightly stuck to the PEP film at the bottom of the tray.

After draining and filtering as much resin as I could (and spilling a fair bit and cleaning that up—ugh!) I cleaned the tray and found little bits of solid resin stuck to the film all over. It looked to me like one stuck deposit had been the cause of missing volume in two of my prints.

One of the stubborn spots left over after my initial attempts at cleaning the resin tray screen.

“Fixing” this involved alcohol and careful scraping with the—included—plastic scraping tool, and then wiping away the alcohol and detritus and allowing it to air dry. The results looked pretty good, but on inspection the PEP screen is quite scratched up now.

So, with this in mind, I decided to track down a decent amount of pure isopropyl alcohol, replacement PEP film, and more and—I hope—better filter cones, and then I will try it again.

(These links are not an endorsement. I provide them because I found identifying suitable items on Amazon to be quite tricky—and getting them from China was going to be slow and quite exensive.)

To be continued…