Introduction: 3D Printed Loaded Dice - Teaching Probability

There are two MAJOR software/hardware items that are needed to use this instructable in your classroom - 1) a 3D printer and 2) a slicer that is capable of setting different infill levels for parts of a model. I used the Makergear M2 3D printer (though any machine should work) and Simplify3D to slice the models. Any .STL file for dice can be used from websites like Thingiverse. For those looking to differentiate or add a skill layer, you could have the students create their own dice in TinkerCAD or Fusion360.

The key to this project is not the dice themselves, but how you control the INFILL while it prints....

Step 1: Infill Percentages

Infill is the ratio of empty space to plastic INSIDE your 3D printed part. Simplify3D has a "Variable Settings Wizard" that allows you to select a specific height on the model to change print settings. You may do this if you are using 2 hotends and multiple colors or filaments. I chose to vary the infill percentage on one of the die. The resulting dice look identical to one another and even feel identical. However, one of the die is weighted to one side.

Step 2: Printing

While printing I rarely watch the entire print. But for this print I make sure to check in every once in awhile as I can reference where the "Switch" in infill as looking at the dots on the side of the dice. The pictures show the beginning of the dice with the same 10% infill and then shortly after the switch where one die switches to 50% infill. Finally, when the dice are printed you cannot tell the difference. ***DO NOT USE TRANSPARENT FILAMENT as you can see the infill pattern**

So now what do I do as a teacher? Do I...

a) Swindle my students out of their lunch money

b) Find a unique PBL lesson for Probability and Distribution

c) All of the above

Step 3: Using in Your Class

Depending on your grade level and pedagogical approach, you might approach this different ways. You could tell students that one of the dice is loaded and that they need to figure it out. You could have students play games and keep track of the rolls to see if they notice one die not behaving properly. Whether you go full lecture or complete inquiry, this project will work. Consider having students keep a data table of MANY rolls of each die and them represent them in some visual distribution. Time after time, the data shown in the charts above come out to show that something isn't quite right with one of those dice......ENJOY!

Step 4:

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