Project: Bridge Building with 123D Design

by MakerBotLearning, published

Project: Bridge Building with 123D Design by MakerBotLearning Jun 18, 2015

Educational Thing


This project, found in MakerBot in The Classroom (http://www.makerbot.com/education), focuses on designing 3D printed connector pieces for building a balsa wood bridge. You can download the entire lesson, 123D_Design_project.pdf, from the Thing Files.

To download 123D Design, visit http://www.123dapp.com/design.

In this project, you and your students will learn how to use a free program called 123D Design. 123D Design is a solid modeling tool that uses basic shapes and sketches to build objects. It’s useful for any project that requires specific dimensions and/or multiple interlocking parts. The following sections outline how you can incorporate 123D Design into engineering, physics, and specifically bridge building units. We’ll learn how to design 3D printed connectors that can be used to assemble a bridge structure. We’ll also explore how 3D printing can affect the structural strength and integrity of your models.


Overview and Background

Students will design and build a scale model of a bridge using only balsa wood, 3D printed connectors, and glue. In the Investigate portion of the project, students will research various bridge designs and begin brainstorming their own. Then, in the Explore and Create sections, they’ll learn how to use 123D Design to model different types of connectors for their bridge. Finally, they’ll assemble and test their bridge for structural integrity. In Further Activities, they can take this project to the next level by building and testing other structures using a similar process.


Students should walk away with knowledge of:

  • Understand bridge structures
  • Identify the similarities and differences between various bridge designs
  • Define trusses and their importance
  • Explore how different geometric shapes handle force
  • Consider the economics of building objects with material and price limitations
  • When to take advantage of 3D printing versus using existing materials
  • Overhangs and bridging
  • Impact of print settings on model strength and material use
  • Importance of infill, shells, and print orientation

CCSS.ELA-LITERACY.RST.6-8.7: Integrate quantitative or technical information expressed in words in a text with a version of that information expressed visually (e.g., in a flowchart, diagram, model, graph, or table).

CCSS.ELA-LITERACY.RST.6-8.9: Compare and contrast the information gained from experiments, simulations, video, or multimedia sources with that gained from reading a text on the same topic.

MS-ETS1-2 - Evaluate competing design solutions using a systematic process to determine how well they meet the criteria and constraints of the problem.

Lesson Plan and Activity

The entire lesson is laid out with pictures in the .PDF downloadable in the Thing Files.

Step 1: Introduction Lesson

Bridges have been used for a very long time to allow transportation over difficult geographical areas. Bridge building involves a lot of very precise engineering because the structure needs to be able to withstand weight, heavy use, and environmental impacts. In this section, students will research different types of bridges to find out the strengths and weaknesses of each, as well as explore how bridge design has evolved through time.

  1. Have your students research existing bridges in use today. Explore the following types of bridges. Prompt the class to explain the strengths and weaknesses of each: Arch bridge, Beam bridge, Truss bridge, and Suspension bridge.
  2. Find a non-bridge structure that incorporates similar designs to one (or more) of the bridges your class has researched. For example, the Eiffel Tower in Paris, France.
  3. Once the students have researched and compared bridge designs, have them research the Tacoma Narrows Bridge to see an example of a bridge design gone wrong.
  4. Before venturing into the Create sections, prompt your students with the following:
    • You’ve been tasked as a newly hired civil engineer to create a next-generation bridge for your community. With the assistance of 3D printing and your knowledge of 123D Design and bridge construction, you’ll use balsa wood and 3D printed connector pieces to build a scale model of the bridge and test it to discover how much weight it can hold.
Step 2: Modeling strength test beams

See video below and download 123D_design_project.pdf from the Thing Files.

  1. When engineers design large structures like bridges, they need to determine the appropriate size, shape, and materials to use in construction. They accomplish this by researching, testing, and analyzing a lot of different parts until they find the right mix of strength and weight.
  2. Sketch a rectangle
  3. Extrude the sketch
  4. Use Sketch and Extrude to modify the test beam
  5. Modify more test beams
  6. Print in two orientations
  7. Perform a Stress Test on each test beam
Step 3: Design a Four-Point Connector

See video below and download 123D_design_project.pdf from the Thing Files.

  1. When building a large project, it’s typical to assemble the structure from a variety of different materials. Using the power of 3D printing, we can create custom connectors to experiment with new and interesting bridge designs. Balsa wood will provide the main structure, and 3D printed components will allow for unique customization. By the end of this section, you’ll have created and printed a simple four-point bridge connector, which you can later modify to fit your design criteria.
  2. Measure your bridge components
  3. Use Primitives to build your connector
  4. Extrude into the block to create a hole
  5. Add a third connection point
  6. Add a fourth connection point
  7. Add strength using the chamfer tool
  8. Save, Export, and Test your four-point connector
Step 4: Design a hexagonal connector

See video below and download 123D_design_project.pdf from the Thing Files.

  1. Sketch and extrude a hexagonal prism and a rectangular bar
  2. Snap the bar to the hexagonal piece
  3. Pattern the bar around all six sides of the hexagonal piece
  4. Subtract the bars form the hexagonal piece to make holes
  5. Save, Export, and Print
Step 5: Design an arc connector

See video below and download 123D_design_project.pdf from the Thing Files.

  1. Sketch and Extrude an arc-shaped object
  2. Create and merge a double-arc shape
  3. Hollow out the four ends of the double-arc shape
Step 6: Design Additional Connectors

See video below and download 123D_design_project.pdf from the Thing Files.

  1. Imagine new types of connectors that will help you design your bridge, and use your 123D Design knowledge to achieve them. Experiment with 123D Design tools and see what other kinds of connectors you can make. Remember to print sample parts to test-fit your balsa wood before printing large quantities of connectors.

Step 2: Modeling strength test beams

Step 3: Design a Four-Point Connector

Step 4: Design a hexagonal connector

Step 5: Design an arc connector

Extension Activity

Design, Build, and Test a Bridge
  1. Students can work in teams to design and build bridges using their 3D printed connector pieces.
  2. Have your students start by sketching out their ideas on graph paper. They can label their sketches to indicate the materials they plan to use for each element of the bridge.
  3. Make sure the students know what criteria will be used to test and evaluate their bridge designs. Some options are size, bridge weight, material use, weight that the bridge can withstand, and aesthetics.
  4. Finally, have the students test out their bridges according to the judging criteria.
  5. If there’s time, ask the students to improve their bridge designs in a second round, to see if they can raise their evaluation scores.
  6. Enthusiasts can take things further by exploring print-in-place hinges and mechanisms to create a drawbridge, or by creating extra 3D printed parts to reinforce or decorate their bridges.
Create upcycled structures with 3D printed connectors
  1. Use 3D printed connectors to create new structures out of recycled or found materials.
  2. Find materials for building, such as dowels, leftover art supplies, paper towel rolls, and items from the recycling bin – whatever you have on hand. Try to find objects that you have a lot of, or that have similar types of ends or areas for connecting.
  3. Have the students brainstorm about what they can make with the found materials. An Eiffel Tower? A skyscraper? A spaceship? Different building materials will be suitable for different types of structures, so think about what each material could best be used to build.
  4. Have the students use 123D Design to build connectors for attaching and assembling the objects into new structures. What kinds of connectors are needed for the types of objects that you found?

Skills Learned

  • Engineering

Duration of Lesson

  • 1-2 weeks (likely more if you want to include the extension activity) - Groups of 4, each group designs, prints, and tests 1 bridge


To prepare for this lesson you will need the following supplies:

  • Computers with 123D Design downloaded and installed
  • Materials:
    • Balsa wood strips (1/8 x 1/8 in) or something similar (toothpicks or popsicle sticks can also work)
    • Wood glue
    • Graph paper
    • Weights (brass weight set, bricks, etc.)

Rubric and Assessment

Knowledge Checks
  • What are the different types of bridge structures? What are their strengths and weaknesses?
  • How does the shape of a bridge determine the amount of force it can withstand? What geometric shapes are commonly used in bridge design?
  • How do print orientation and settings affect the strength of your printed parts?
  • What considerations are important when designing parts that fit together?
  • What are two different ways to create a 3D object in 123D Design?


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