Meet Launchy, the little 3D-printed siege weapon that wrote history (i.e. automatically yeeted a ball) when its plate cooled!

Born from a frantic 45-minute OpenSCAD coding session, Launchy 1.0a came within a hair’s breadth of glory, captivating over 650,000 viewers in my original Reddit post. Later, equipped with a face and a beefier rocker, 1.0b proved its potential with a successful launch, promoting Launchy to version 1.0. It didn't launch a ball—it launched a movement! …Fine, it totally launched a ball.

Launchy Launched!

History was made on February 27, 2025 at the Launchy Launch Party livestream (announced here)! Watch the undisputed launch at 3:49:14 on the P1S (60°C, 0.8mm ball contact radius) and the earlier questionable launch at 2:03:47 on the A1 (65°C, 1.75mm ball contact radius).

A BIG THANKS to everyone who attended, especially those who printed along. fullraph also made history, achieving the first flawless launch with Launchy staying on the build plate!

How to Fire Launchy

• Step 1: Print Launchy.
  That’s it—just print and brace yourself. Minutes? Hours? Suspense HBO can't touch.

Original Detailed Schematics

A Benchmark?

Launchy is also a unique boolean benchmark, delivering a clear hit-or-miss result. Unlike subjective benchmarks that leave you guessing, “Did it print well enough?” Launchy either launches that ball or it doesn’t—zero ambiguity.

RAKM Application Space

Beyond a playful concept, Launchy represents the first example of what I’ve termed a Release-Activated Kinetic Model (RAKM), a new application space in 3D printing. These models exhibit functional motion triggered by the weakening of adhesion, enabling gravitational energy to drive kinetic action.

Potential applications are extensive, often resembling Rube Goldberg devices, such as automatically rolling dice, self-initiating marble runs, or prints that self-clear from the plate. And yes, projectiles—lots of projectiles! I’m excited to see what the 3D printing community comes up with—post your ideas below!

My Print Settings

I’m running a Bambu Lab P1S and an A1, both with textured PEI plates and Bambu’s basic PLA. The 3mf includes everything, but for raw tweakers:

• Position on plate: Rotate to face forward and place far back so it doesn’t fall after firing.
• Infill: Rectilinear—rocker top half at 98%, rest at 10%.
• 0 top shell layers for the rocker top half (otherwise it tends to get knocked over).
• Speeds: Initial layer and initial layer infill 50mm/s, walls and other infills 100mm/s.
• No brims (small contact surfaces baked in).
• Arachne wall generator.
• Turn off aux fan.
• Build plate temperature + ball contact area size: Launchy 1.0 achieved launches at 60°C on the P1S (0.8mm ball contact radius) and 65°C on the A1 (1.75mm ball contact radius). Bed-slingers typically require slightly hotter temperatures and a larger ball contact radius to maintain adhesion.

Whatever settings you try, make sure your build plate is freshly clean!

Minimizing Launch Time

Launchy launch times vary considerably. It’s highly dependent upon your settings, equipment and environment (e.g. absolute room temperature / room temperature fluctuations). I’ve seen release range from under an hour to 10+ hours.

It's still not clear to me if hotter or cooler plate temps are best. Hotter temps (up to a point) improve the chance of a successful print, but assuming the print completes, which is better for launching earlier? My contradictory thoughts:

• COOLER plate temperature: reduces adhesion (also risks print failures)
• HOTTER plate temperature: strong adhesion *during* printing is a good thing, and a larger temperature gradient means a more extreme post-print cooling process which could better break the adhesion; a hotter temp also allows for smaller contact areas to successfully print

I have similarly contradictory thoughts on ball contact area:

• SMALLER contact area: less initial adhesion
• LARGER contact area: more material could build internal tension, aiding release - bigger objects often release better in my experience

Launchy is shy – it can take experimentation to find the magic incantation required to motivate him! Hopefully others will experiment and help me firm up the guidance.

Add Your Profile!

My settings are a starting point. Printer, plate, and filament combos will make or break it. Nail a config? Upload your print profile and equipment details here! Let’s crowdsource a Launchy cheat sheet!

Tweak Launchy

For advanced users, I've also uploaded the OpenSCAD script I wrote to generate Launchy along with the vector graphics (.svg files). Download Launchy.zip to get started tweaking it.

Make It Yours

Got ideas? Feeling inspired by Launchy? Remix it, redesign it—derivatives are welcome! I want to see more effective & efficient Launchys (time / distance / accuracy contest opportunities!), Benchys and poop emojis soaring through the air, dueling printers, and more. So many possibilities!

Considering your own Release-Activated Kinetic Model? I’m happy to share what I know. If you design your own Launchy or RAKM, just:

• Ditch the “Prime Tower Designs” stamp—it’s my mark.
• Link back to the original Launchy page—mandatory for direct derivatives of my model/script; just cool (but obviously optional) for scratch designs using the RAKM concept.
• Bonus: Consider doing me a solid by linking to my profile page.

Launchy Superfan?

Proudly tell the world with the Launchy Launch T-Shirt! In the true spirit of Launchy, I threw the shirt design together in under an hour (including the time to launch my very first merch store) - about the same amount of time I spent designing Launchy 1.0a!