One of the wonderful teachers at New Ulm Public Schools let me into her classroom recently to talk to her students. The topic? 3D printing and math! Maybe that doesn’t sound very exciting to some, but I assure you I had fun, and I am pretty sure the students enjoyed it too!
Janelle Woodbury teaches math to 7th and 8th graders in New Ulm. We just happened to meet in New Ulm one day, and I mentioned that I could bring my 3D printer to her class and talk about some of the math involved in 3D printing. She thought it was a great idea! (We knew each other from MathCounts – a wonderful program if you haven’t heard of it.) I am glad she was willing to give me a chance, and I admire her desire to expose her students to ways people can use math to do interesting things.
The day came and I took my 3D printer to her classroom. I set it up and let it print a “Marvin” while we talked about 3D printing and math.
Before we talked about how 3D printing worked, I gave examples of things you could make with a 3D printer. Some of the possibilities are parts to fix things, toys, art, useful gadgets, and more. I showed them some of the things I printed and then asked them to write down things they might want to print. They had a lot of great ideas – from useful gadgets and toys to jewelry and models of pets. I also gave them each a “Jimmy” that I had printed on my printer. (“Jimmy” is a robot-like little guy designed by my son, Luke.)
Then we talked about extrusion – a key part of 3D printing. Extrusion is a process that takes a soft material and pushes it through an opening with the desired shape. The material needs to be soft enough to go through the opening, but hard enough to keep its shape afterward. I compared this to using whipped cream in a can. You move the nozzle and the whipped cream comes through a star-shaped opening and keeps that shape – until you eat it of course! With 3D printing, the plastic is heated until it is soft enough to go through the nozzle. Then you want the plastic to cool so that it stays where you want it and in the shape you want it.
After extrusion, we talked about how 3D printing is done in layers. The printer forms one 2-dimensional layer at a time and stacks them one on top of another. This makes it easier because we don’t have to think in all three dimensions at once. We asked the question, “What would some of the layers look like if we print Jimmy?” We drew some examples on the board.
So now we can extrude plastic and we know we can make one layer at a time to create our 3D shape. How do we get the machine to move the extruder around and form those layers? We talked about stepper motors and how to change the circular motion of the motor into the linear motion we need. Then with the help of a few students, we acted out how each motor pushes or pulls the extruder to make the shapes we want. My intention with that little exercise was to help them visualize what the printer was doing.
Finally, we talked about the calculations the microcontroller does to move the motors. We looked at the number of teeth on the pulley, the space between teeth on the belt, and the angle of each step on the stepper motor. Then we calculated the number of steps the stepper motor needed to take to move the extruder 1mm. This means we know how to move the extruder to a precise position anywhere on the build platform. Knowing that, the rest is simple. We just move the extruder from place to place and make the shapes we need for each layer in our 3D object!
Throughout the class, I asked them to write answers to questions about what we had just discussed. After looking at their answers, I was impressed. I think a lot of them got it. It was a lot of information and perhaps a little overwhelming, but I think they learned some things. Even better than that, I hope some felt encouraged to use their brains and math skills to build or do something interesting. That’s exciting!
One last thing – My last question to them had nothing to do with 3D printing. I asked them what they thought of my mustache. (It’s a handlebar mustache.) They had a lot of great responses. One student even drew me a picture. How cool!