Overview and Background

I asked my son's preschool teacher if I could bring in my 3D printer to share with the class and she was stoked by the idea! As we spoke more we thought it would be nice to use 3D printing as not just a goal of the lesson, but also as a support for the current science unit- life cycles.
The lesson went terrifically and I was amazed by how attentive the children, ages three through five, were during the lesson and how inquisitive they were when I opened the floor to questions. My favorite question was from an adorable little one asking if I knew that boys can get their hair cut at a salon just like girls. Not quite on topic, but still awesome.

Lesson Plan and Activity

As your printer runs (printing the egg) on a nearby table, give a basic description of how 3D printing works. I used Lego bricks to demonstrate how depositional fabrication works. I also made sure to bring lots of example things to pass around. I emphasized the use of 3D printing as was to solve every day problems, sharing my student designed door stop and playdough tools as examples.
Those lessons can be found here http://www.thingiverse.com/thing:1328211 and http://www.thingiverse.com/thing:1294945
Describe the life cycle of a butterfly, step by step. As each stage is introduced and discussed share the corresponding things and labels. Call up students to place the models and arrows in the appropriate order.
If your timing is just right the egg should finish printing just as you complete the lesson, allowing you to pull it off the printer, pass it around, and complete the life cycle as a group.
Close with a reading of the Very Hungry Caterpillar, by Eric Carle.

Materials Needed

See "Preparation" section

Duration of Lesson

1 session

Preparation

I printed out all items but the egg, which I started a few minutes before the children came in from outside play to keep the lesson to about 15 minutes.

Rubric and Assessment

Not assessment is necessary, and probably not recommended for this age. However, I did hang out and during play time and ask the kids lots of questions to gauge their learning.

References

Complete NAEYC Standards (if you are interested) http://www.naeyc.org/files/academy/file/AllCriteriaDocument.pdf

Butterfly Life Cycle