Download Mineways 7.03 for Windows (works with Minecraft 1.14.2 and earlier). See these instructions for how to run the latest Mineways Windows version on Mac or Linux (there is also a deprecated Mineways 5.10 for Mac - it works only with 1.12.2 and earlier. You're wiser to do it the right way on the Mac).
Mineways lets you export your creations from the Minecraft Java Edition into files you can use for making images, movies, or 3D prints. It is a free, open-source program. You can create 3D prints on your own 3D printer or through a service such as Shapeways or Sculpteo, view your model on the web through Sketchfab, or render with Blender, Cinema 4D (make sure you have a newer version), 3DS MAX, Maya, or other rendering system.
Have a different version of Minecraft than the Java edition? You may be able to convert your world to be readable by Minecraft.
Among other packages, you can export models for use in:
Search the Mineways site:
Rendered with Blender
3D printed at Shapeways
Shared on Sketchfab (click it!)
If you're wondering, Mineways is a hobby of mine, I don't make money on it (just the opposite). In this podcast I talk about why I made it. Short version: for fun! My payoff is seeing what people do with Mineways, so please do send me pictures of 3D prints or renders or movies you make.
Kids like Mineways, too. We've done 2-hour workshops about 3D printing at Parts & Crafts in Somerville, Mass. - here are the presentation slides. I've also presented at Minecon 2016; here's my report, slides, and talk.
BTW, secret tip: click at the top of this page on the teapot and you'll cycle through all Mineways documentation pages.