Today I got to play with a 3D pen. In case you've never seen one, it is a pen that you feed a filament through and the pen heats it up so its plastic and you can start to create things.
You can create hearts, cubes, or pyramid frames, and just about anything your mind can imagine. We use patterns to learn to do it. I decided to make a cube and I drew two squares and two three sided almost squares, then you "solder" them together. While I made it my mind considered how I could use something like this in Math.
Hmmmm, I thought as I looked at the frame of a cube, why can't I make an assignment where I have the students select a 3 dimensional shape, such as a cube, a pyramid, a rectangular prism and then using the design process they could create the frame, write up a report on how they created it, calculate the volume, the surface area, and create a net so someone could make the shape out of paper? They could snap a picture, identify the vertices, the edges and the faces and include that in a write-up. Soooo many possibilities.
The same process of creating a frame model could be used to make a model of the crystalline structure of minerals in a geometry class. Most crystalline structures are made up of 3 dimensional shapes and provides a real world extension.
If you had them create frame models of the crystalline structures, it would require some research and careful planning so you could use the design process on it.
Some of the teachers created plastic glass frames using the pen. They aren't strong enough to hold lenses but are more for fun. You make the glasses by creating a thicker set of lines that you run right next to each other kind of like corduroy and you can get a colorful one with flowers or other things attached to the frames.
Best thing of all, it is only around $100 for the machine and some filament to start. Very affordable.