I want to use a block building 3D design environment with third and fourth graders. Minecraft is the obvious answer, and I have experimented with Printcraft. Printcraft is a Minecraft server customized for producing 3D STL files to print. There is an EU server and a US server available. The software is workshop tested and proved and also available for download if you want to run an intranet instance of Printcraft to sandbox your students' creations. Never has Minecraft and 3D printing been so easy. However, this package requires effort on your network administrator's part to unblock a bunch of different websites that do the heavy lifting when it comes to generating a 3D STL model. How can we make 3D printing easier?
Blokify is a great alternative to Minecraft. Block building in a creative environment. No griefing. Available from the app store.
You can generate a 3D model to be printed by an online service. Alternately, you can go to your local maker space, school, or friend and print your model!
You design your model on your iOS device: check the system requirements before installing on your device!
Tap and build your model. You can email the resulting STL file to yourself to print!