UTPA STEM/CBI Courses/Graphics/A Lesson in Sub-Assemblies - CAD - Snap Cubes

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Course Title: Engineering Graphics

Lecture Topic: A Lesson in Sub-Assemblies – CAD – Snap Cubes

Instructor: Gregory Potter

Institution: UTPA

To visit the Engineering Graphics website click here

Snap-cube puzzle consisting of sub-assemblies

Backwards Design[edit | edit source]

Course Objectives

  • Primary Objectives- by the next class period students will be able to:
    • create a CAD model consisting of several sub-assemblies

  • Sub Objectives- the objectives will require that students be able to:
    • use assembly mates in CAD application
    • create an exploded view in CAD application

  • Difficulties- students may have difficulty:
    • understanding "real world" interferences that the snap cubes will encounter and how that should affect their model

  • Real-World Contexts- there are many ways that students can use this material in the real-world, such as:
    • when designing engineered systems of any kind (specifically parts with similar geometry)

Model of Knowledge

  • Concept Map
    • the students should realize that no matter the complexity of the assembly, it can be reduced to sub-assemblies and then reduced to parts
  • Content Priorities
    • Enduring Understanding
      • students should be able to create and organize CAD files
      • students should be able to use CAD as a design tool
    • Important to Do and Know
      • advanced Assembly techniques (smart mates)
      • familiarity with exploded view techniques
    • Worth Being Familiar with
      • part creation techniques (smart mates & important geometry)

Assessment of Learning

  • Formative Assessment
    • In Class (groups)
      • students use snap cubes to create their own puzzle cube design
      • each student in the group is required to draw a piece of the puzzle (one sub-assembly)
      • group decides how the overall assembly is produced
    • Homework (individual)
      • overall assembly of puzzle cube assignment
  • Summative Assessment
    • projects (Lincoln Log House and IKEA furniture) on Exam 2 and Final Exam using skills learned during this lesson

Legacy Cycle[edit | edit source]


By the next class period, students will be able to:

  • create a model consisting of sub-assemblies

The objectives will require that students be able to:

  • use advanced assembly techniques


Give students an advanced lesson in sub-assemblies using snap-cubes as subject matter. This exercise will take place during the eighth week of Engineering Graphics Lab. It is designed to give the students tactile experience making the shape with Snap Cubes before attempting to create a CAD model. This assures that the student is visualizing the shape accurately before the parts and assemblies for this lesson are started.


Give the students dimensions of a Snap Cube so that they are able create a part file in SolidWorks. From this, they can create an assembly of 3 sub-assemblies of a puzzle cube. At this point in the course, the students already posses the CAD skills to complete the basic task: creating sub-assemblies and using them to create an overall assembly. However, the lesson is about advanced techniques where the students are using “smart mates”. This technique saves time and effort when creating assemblies containing more of one part or similar parts. When the students are building their real-life snap-cube puzzle cubes, they should be thinking about how to assemble their 3D model sub-assemblies, and ultimately the overall assembly of the cube puzzle.


Ask students to create puzzle part shapes from snap cubes first. They can then create a sub-assembly of each puzzle piece using their snap cube part drawn earlier.

  • Possible questions:
    • What type of tolerance fit is between each snap cube?
      • the snap-cubes have an Interference Fit between the mating surfaces. This question is meant to reinforce the regular EG curriculum with a real life example.
    • How do the pieces stay together?
    • What keeps them lined up with each other (sides flush)?


Ask students to model the entire puzzle cube assembly using component sub-assemblies.

  • Possible questions:
    • Do the sub-assemblies stay together when constructing the entire cube?
    • Why should you make each puzzle piece as a sub-assembly?
    • Do the snap-cubes interfere when assembling the puzzle components?
    • What surfaces are being used to mate the parts together?


Assign homework designed to exercise the skills learned during this exercise. This would include improving the “smart mates” for their models. After they have watched the tutorial, they will be able to greatly improve their snap-cube parts’ “smart mates”. This skill will be advantageous while working on the next lesson and the final project.


The students are assigned a final project at the end of the semester. They will be required to use the skills acquired during this lesson.

Pre-Lesson Quiz[edit | edit source]

Snap-cube puzzle consisting of sub-assemblies

Students will be shown a design for a puzzle cube for discussion. Snap-cubes are handed out to stimulate real world connections. Students can build their puzzles for real, then build them again using a CAD program.

Test Your Mettle Quiz[edit | edit source]

Students are required to design their own puzzles in CAD for homework. They will also be required to use the skills learned during this lesson while completing projects later in the semester.