Updated: Sep 16, 2019
Waffle Maker Lesson Plan
Once students have learned the basics of 3D design using Tinkercad, they will be learning the Engineering Design Process. As a part of the process they will be designing 3D printed parts that fit into and existing object in the design; the waffle. By adding the 3D prototyping aspect to the lesson, students are able to make changes and see the results in real-time. Students will learn about horizontal expansion in filament and how to resize and taper parts to create a better fit. They will then design parts to fit in the waffle and compete in a contest to see who has the most creative waffle.
NGSS Engineering Standards
MS-ETS1-1. Define the criteria and constraints of a design problem with sufficient precision to ensure a successful solution, taking into account relevant scientific principles and potential impacts on people and the natural environment that may limit possible solutions.
ETS1.A: Defining and Delimiting Engineering Problems
§ The more precisely a design task’s criteria and constraints can be defined, the more likely it is that the designed solution will be successful. Specification of constraints includes consideration of scientific principles and other relevant knowledge that are likely to limit possible solutions. (MS-ETS1-1)
ETS1.C: Optimizing the Design Solution
§ Although one design may not perform the best across all tests, identifying the characteristics of the design that performed the best in each test can provide useful information for the redesign process—that is, some of those characteristics may be incorporated into the new design. (MS-ETS1-3)
MS-ETS1-2. Evaluate competing design solutions using a systematic process to determine how well they meet the criteria and constraints of the problem.
How do criteria and constraints apply to an engineering design challenge?
Why is it important to brainstorm, plan, and sketch out a design before constructing a prototype?
Lesson Plan and Activity
Discuss the Engineering Design Process steps with the class
Discuss thermal expansion and the COEFFICIENT OF LINEAR thermal expansion (CTE, a, or a1) which is a material property that is indicative of the extent to which a material expands upon heating and contracts when it cools. Over small temperature ranges, the thermal expansion of uniform linear objects is proportional to temperature change.
Have students turn and talk to their partners about how this expansion & contraction could affect the accuracy of how 3D printed parts fit together.
Horizontal Expansion Setting Introduction for Better Fit:
The shell setting adjusts the thickness of outside walls (on the X/Y axis) of the model. You might want to modify the shell setting based on the material you are using. All plastics shrink as they cool (remind students of thermal expansion). Filaments like PLA, shrink a small amount, but others, like Nylon and ABS, shrink more extensively.
The Horizontal Expansion setting will allow you to adjust the size of your 3D print in the X/Y dimension to compensate for the change in size that happens when the plastic shrinks as it cools. The ability to control the horizontal expansion is important when you're working with precise sizes.
Enabling Horizontal Expansion in Cura
To enable Horizontal Expansion, Click the Gear Icon on the Shell Menu and enable the Horizontal Expansion check box. When you close the options menu, the Horizontal Expansion setting will be added to the Shell Menu.
A positive Horizontal Expansion value will add to the dimensions of your model. You should use a positive value when your printed model is smaller than you expected.
A negative Horizontal Expansion value will reduce the dimensions of your model. Use a negative value when your printed model is larger than expected.
Try it yourself
Download and print this:
Simple 20mm cube by Skimball
Each side in the X/Y plane should be exactly 20mm after printing. Take a pair of calipers and measure the dimensions. If your print is not exactly 20mm x 20mm, use the Horizontal Expansion setting to add or subtract the difference between the target value and what you have. Slice and reprint.
Reflect: What happens?
Now that students understand how to adjust the horizontal expansion setting in Cura for a better fit they will start to brainstorm designs for their Waffles.
Give each student a waffle and pair of calipers and have them measure the squares & circles, discuss the importance of accurate measurements when designing 3D parts that fit into existing pieces (each square in the body is 10x10mm and the circles around the edges are 10mm in diameter).
Engineering Design Challenge: The waffle must be the center of the construction and parts designed by the students must fit accurately in the waffle. They can design their waffle to be anything they want.
Provide graph paper for students’ use.
Students must turn in an initial sketch with dimensions, first prototype, and final product.
Using graph paper, brainstorm and sketch at least 4 different design ideas
Examine each of your design ideas and answer the following questions:
Does this design meet all of the criteria for the project?
Is the design easy to print?
No small features that are easily broken?
No need for supports?
No small text that will not be clear when printed?
Using Tinkercad, create a model of your design.
Once the initial prototype is finished, evaluate your prototype by answering the following questions:
Is the design the correct size? (10mmx10mm squares / 10mm in diameter)
Has the horizontal expansion setting been utilized to ensure an accurate fit of the parts into the waffle?
Are all of the features/designs clear and neatly printed?
Is the design designed so that it is not delicate or easily broken?
If you answered no to any of these questions make changes on your design to address any of the issues.
If you answered yes to all of the questions, take a look at your waffle. Find one thing that can be improved. Make that change to your original design.
Turn in your improved design.
Complete a reflection paragraph about this project including the following:
What was one thing that surprised you about the Engineering Design Process and the waffle design?
What was one thing you found easy to do in this project?
What was one thing you found difficult to do and why?
Describe how thermal expansion and contraction affects fit of 3D printed parts?
Computer or Chromebook
Duration of Lesson
3-4 Periods (45 minutes)
Rubric and Assessment
Students will evaluate their designs (using the criteria and constraints) in a summary paragraph after the completion of the first prototype.
Students will complete a reflective writing paragraph at the conclusion of the lesson.
Waffle Maker Connector Guide
The connectors in this guide cover the different pieces for the Waffle Maker project. Each of these pieces is designed to work with each other and be printed without supports. This helps educators and student print the connectors quickly. Many of these pieces print in 15-30 minutes allowing students to print pieces in the same class.
Use horizontal expansion to allow pegs to fit your waffle maker. Make note of the expansion used because all other parts need to have an equal amount of expansion to make them fit with the connectors.
Use a raft - “Elephant Footing” of parts can make them not fit into the Waffle Maker correctly. Using a raft almost always eliminates this. Parts also print more reliably on the raft than without one.
Use a tuned printer. - Make sure your printer is tuned and printing the same tolerance. If you have multiple printers in your lab make sure that the printers are tuned equally well.
Use low infill. - Since these parts are not structural in nature, 5% to 10% infill is sufficient in many cases. Start small and increase if your part requires a load.
.2 and .3 layer heights (or anywhere in between) is sufficient for Waffle Maker lessons. This will allow you to print faster.
Save your parts! When the project is complete save your parts for the next class.
Share your parts! Use #WaffleMaker - <project name> in Tinker Cad so others can benefit from parts you and your students create. Share your creativity.
Create your own components!
The Waffle Maker project is designed to share creativity and projects amongst STEM
educators worldwide! This gives you more resources to draw against in your projects using Waffle Maker.
The waffle maker connections use standard tinkercad connectors. This allows you to develop your own pieces to connect to Waffle Maker.
This will let others use the Tinkercad search to simply look for “WaffleMaker.
Just remember to make your piece public so other educators can find your component. This is done by using the gear under design properties and setting it to public.
We can’t wait to see what components you and your students build and publish. #WaffleMaker!
Body Pegs & Connectors
The body peg is used to connect items to the face. The body peg is printed as shown and designed to print without support. Multiple pegs should be printed as a connector to allow you add items to the face. Two versions a large and small are available depending on the amount of load on the peg.
Face items work well with small pegs. Structural items work well with larger pegs. Students can then create any object that has a round hole on the bottom to attach to the face. This prevents supports from needed to be used on objects connecting to Waffle Maker.
Use horizontal expansion to tune your peg to fit your Waffle Maker body.
Outer Rim Peg
The outer rim peg is the peg designed to be placed into the outer rim of the Waffle Maker. From there, students can use the ball connector to connect pieces to these pegs. These pegs are designed to be printed as show and without support. The pegs can be modified with horizontal expansion but take care in that modifying these can modify the ball joint as well. Subsequent ball joints will need changes in horizontal expansion in order to accommodate the changes in this peg.
The leg works on both the left and right leg and connects to the outer rim peg.
Standard Arm / Connector (Male)
The standard arm / connector is used to connect items together that also link to the outer rim peg socket. This is designed to print without support. A brim works very well for printing this particular part. Rotate the part 90 degrees on its side for best printing. Using a larger layer height helps when printing this part.
The standard arm / connector is used to connect items together that also link to the outer rim peg socket. This is designed to print without support. This can print on its side or as shown.
The Hand prints as show and connects to the standard arm components.
The Peace Hand prints as show and connects to the standard arm components.
The Eyes print as show and connects to the standard arm components. Note that the eyes have holes at the bottom that are connected to the body peg. These do not require supports to print. A filament change at the end can give you a different colored iris. You can also paint that portion.
The Top Hat prints as shown and connects to the standard outer rim connectors. Note that the Top Hat has a ball connector on the inside that allows you to connect the hat. This does not require supports to print.