Remixing a d20 countdown dice holder in Blender - BoltFactory plugin

I figured I would share some of the remix process of my latest project.

The final result - whoops, where is my d12?

You can find the final results here on Thingiverse. The original version was done by the user kittka on Thingiverse, a little larger and using magnets.

My original remix that I didn't share, was scaled down and using different magnets. Sadly, the thin magnets I normally use for my projects did not hold the d20 together, as it jostled around in the gaming bag. Remix #2, I used more powerful magnets in the base where the d20 had more room.

As this wasn't a major remix, I didn't bother posting it. There were still minor issues - knocking the d20 at just the wrong angle, it would spill all of the dice out. I considered replacing one set of magnets with a post and hole, so you'd have to pull it apart vertically...but it was in a design backlog.

Enter the Puppy

My friend hosting D&D has a pup that likes to chew. Alfred climbed into my bag, pulled out my d20, and chewed on the lid...breaking off part of the top. Fortunately, none of the magnets were swallowed, no PETG was eaten, but I now needed a new d20.

Post-Alfred

Enter the BoltFactory plugin

Blender 2.8 has a bunch of plugins, most of which I had played with in the earlier versions. I had not experimented very much making bolts in the past. I did make a screw thread once using arrays, but...it was work. Boltfactory is stock, just needing to be turned on. Edit>Preferences>Add-ons, then type in "bolt".

Once that's turned on, you can shift-A to create a mesh, and select "Bolt" at the bottom, which gives you this handy bolt creation menu.

I used the default bolt generated. To get the corresponding nut, just change the Model: BOLT to Model: NUT.

I scaled them both up at the same ratio, to fit to the die. From there, I made a wide-but-not-tall cube to boolean-intersect a thread section from the bottom of the bolt (slightly bigger than the nut part I was cutting out), and a boolean-intersect from the nut. I printed a prototype, to see if my .24 mm layer height and .5mm nozzle would provide good enough tolerances for the scaled-up threads. Success!

Orange nut, purple bolt, with a longer orange test bolt

Scaling up the nut/bolt gave me a really "chunky" thread. Easy to print, as well as not needing a lot of turning to open. (Turned out to be about 108 degrees of turning.) Enough to have a tight seal, but not enough to make it too much effort.

The Real Work

It gets tedious and ugly after this. I dissolved all of the vertices that held the magnets, and made smooth edges to merge with future bolt/nut sections. There were three design issues to overcome, and in my first time doing this, I didn't come up with a clean system.

1. The top needs to be flush with the base, plane to plane (bottom of the top, to the top of the base)
2. The number faces on the top need to match the "spin" of the bolt into the nut
3. The number faces on the top need to be flush with the number faces on the base

The first one was awkward — the top and base needed to be rotated the exact amount. I probably should have just reimported the original, but I continued my original remix. They needed to be the same z-plane coordinates on each facing plane. I checked the z-coordinates of the vertices, and rotated on x/y axis to balance opposite sides. After that was flat, I merged the bolt and nuts (skipping some finer details here). 

I printed the d20 bottom, as the nut part wasn't going to change. Printed a top, testing the "right amount" of bolt.

The second design issue should have been more manageable in Blender, but I didn't trust virtual tolerances. To match up the faces, I would rotate everything BUT the screw portion. It's easiest if you dissolve the unnecessary edges on the bottom of the top - otherwise the spin might get some of your edges cutting into other edges. Again, printed a couple more to get the alignment of faces correct.

The third design issue, I noticed that the top wasn't completely aligned with the bottom, on the x/y axis. I could run my fingernail up the face from #6 into #5, but it would catch...and there was one millimeter-ish gap on the #2 to #10. A couple of printed tops later, it matched.

Closed