This activity is the first part of a 3D printing curriculum.&nbs= p;

=20**Goal:**

The idea of additive building processes must be introduced to explain 3D= printing. Additive processes include building with legos, or sta= cking objects together. Whereas subtractive processes include carving, CNCi= ng, or machining.

=20**Activities:**

First the idea of shapes and 3D geometry must be introduced. T= his can be done in many ways depending on the students' previous&= nbsp;experience with 3D shapes. The goal of the activity&nbs= p;is to have students create several 3D shapes out of 2D shapes stacked on = each other.

=20Simplifying additive processes into easy to understand concepts is key. = Several 3D shapes can be broken down into layers or slices which are the sa= me as the 2D version of the shape. Such as: Cubes-Squares, Spheres-Cir= lces, Pyramids-Triangles. The 3D shapes can be built by adding small slices= of the base shape. As an example in class, pieces of paper or cardboard, s= mall 1x1 lego blocks, and playdoh can be used to make 3D shapes via lots of= small layers.

=20To introduce the idea of 3D geometry have students name several 2D and 3= D shapes. Then have them connect the related shapes to create 3D shapes. In= troduce the idea that the size of the 2D shape can change to produce differ= ent 3D shapes. For example the size of a square shrinks as the height of a&= nbsp;pyramid increases.

=20After introducing the idea of additive 3D shapes give each student a tub= of playdoh or other materials. Task them with creating various shapes such= as spheres, cubes, rectangular prisms, square and tria= ngular pyramids by creating the base 2D shapes needed to build the 3D = shape.

=20Give the students plenty of time to play with the materials and ask them= to make many different shapes over the course of the class.