Minecraft and 3D Printing: Skeleton Slingshot!

If there are three things my STEM students love, these are Minecraft, 3D Printing and ballistic projects (like catapults, rocket launchers, crossbows, and so on), so I decided to make something integrating these three concepts.

Actually, I like Minecraft, too. Even I'm Minecraft Edu teacher. I remember my first days, when I just started playing Minecraft and I said that to two of my students, 8 years old kids. They looked at me with fascination and said "Mister Mario plays Minecraft... WOOOOOOW!" (It's not normal in this country adults to play "childish things" like Minecraft.)

Then I proudly showed them my first construction: an underground (natural) cave (my home) with a secret access through a lake. Even I flattened the floor with the best cobblestone I could find!

Their fascination turned into disappointment, and trying to not hurt my feelings, one of them slapped my back and said with a slow and condescending voice "goooood Mister Mario... keep practicing..."

That was two years, 150 Creepers, 530 Zombies, and 1 giant pyramid (with walls, Redstone traps and a Nether Portal) ago.

If there is one mob that always annoys me to death, is the Skeleton, with his ugly face and uglier arrows. That gave me the inspiration for this project: a 3D printed Skeleton that works as a slingshot to throw NERF arrows!

The longest part of the project was to design the Skeleton on Tinkercad. After printing it, it's only necessary to add a rubber band and an arrow (made from a straw and a NERF dart) and ask some friend to help you as test dum... quality inspector for my creation.

NOTE: As any project involving ballistics, don't aim or shoot to persons or animals. It's dangerous!

(I'm participating in the Minecraft Challenge 2018. If you like my instructable, I will greatly appreciate your vote. Thanks!)

Step 1: Design

I created the Skeleton from scratch, using Tinkercad and internet photos from the game and the action figure as reference.

I imagined this figure was made of minicubes of 3mm side, and the head was a cube measuring 8 minicubes on each side. Then I extrapolated those measures for the rest of the body.

I measure the diameter from the straw (for the arrow. I will explain more on Steps 3 and 4), being 4mm. So I placed a 6 mm hollow cylinder in the bow's arm, as a barrel, so the arrow can slide freely when launched.

Besides, I designed a small piece ("needle") for the rubber band, to make easier and more precise to grab and launch the arrow.

After finishing the design, I removed the head, redesigned it so later it could be attached to the neck, and lay it and the body over the workplane, so printing will be faster and spending less support material.

You can find the Tinkercad design here!

Step 2: 3D Printing

To print the prototype. I used the Flashforge Finder 3D Printer from the STEM education center where I work (great printer, if you ask my opinion) in low resolution, with Tree-like supports and no raft. It took me 1 hour 52 minutes to complete, and spent 10.06 meters of material.

When it finished, I proceeded to clean the pieces (supports removal), being careful with the bow.

Step 3: Extra Materials

For the slingshot:

Rubber band

For the arrow:

10 - 15 cm hard plastic straw (like the ones used for balloons). You can experiment to find out the best length for the rubber band you are using.
Masking tape
NERF dart with sucking cup (actually, I used a knockoff brand)

Step 4: NERF Arrow

I covered one end of the straw with some masking tape, so it can be inserted in the NERF dart and stay there thanks to the pressure.

Step 5: Assembling the Skeleton

When I tried to attach the body to the head, I realized the neck was too big for the hole I designed on the bottom of the head. So I had to cut and apply some sandpaper to the neck, to avoid wasting this prototype. Test and improve!

This failure was corrected on the Tinkercad design.

(NOTE: being the center of gravity too high, I had to stick the Skeleton's feet to the table using double-sided tape for the photos. )

Step 6: The "Needle"

I inserted the rubber band trough the hole of the "needle". Notice I didn't have to cut it. The needle must stay half way, leaving two loops of the same size.