806 INTRODUCTION TO MANUFACTURING (Goodwin) Unit 4: 3D Design and Printing

Lesson 1: 3D Printed Wrench

Duration of Days: 7

Lesson Objective

Students will be able to reverse engineer a physical object (a bolt) by measuring its dimensions, apply tolerance principles to design a functional custom tool (a wrench) in CAD software, and utilize 3D printing technology to prototype, test, and iterate their design for functionality.

Why must a wrench be designed slightly larger than the bolt it turns (the concept of Tolerance)?
How does "Prototyping" save money and time in the real world?
What geometric features give a tool strength versus features that cause it to break?

Parametric Modeling
Orthographic Projections
Dimensions
Blueprint

ENG.03.01: Use the design process to create a product (Define, Generate, Prototype, Test, Iterate).
ENG.04.01: Create three-dimensional (3D) representations using computer-aided design (CAD) software.
MAN.07.02: Measure parts using precision instruments to verify compliance with specifications (Reverse Engineering).
CT-TE.9-12.4: Identify and use resources (materials, tools, machines) to create a product or system.

Description: This is an activity combining measurement, CAD, and manufacturing.
Phase 1 "Measure & Design." Students receive a randomized bolt. They must measure it with calipers and design a wrench in Fusion 360, specifically calculating the "tolerance gap" (e.g., adding +0.2mm to the opening).
Phase 2 "Print & Test." Students 3D print their design. They physically test it on the bolt. If it is too tight (doesn't fit) or too loose (strips the bolt), they must edit the CAD file and reprint.
Phase 3 "Reflection." Students document their success or failure in a presentation including photos, blueprints, and answers to reflection questions.

Purpose: To teach the reality of tolerance. A perfectly dimensioned "10mm wrench" often won't fit a "10mm bolt" due to material shrinkage and printer inaccuracy. Students learn to design for the process, not just the number.

DOK Level:
Level 3 (Strategic Thinking): Designing a tool where the dimensions are not given but must be derived from another object.
Level 4 (Extended Thinking): Testing a prototype, analyzing why it failed (e.g., "The handle snapped because the infill was too low"), and synthesizing a new solution.

Provide a "Base File" in Fusion 360 that contains the handle pre-drawn. The student only needs to measure the bolt and modify the "head" of the wrench to fit.

Formative: "The Fit Test." The teacher walks around during Day 4/5. The student must demonstrate the wrench turning the bolt.

  • Pass: Fits on easily, turns the bolt without slipping.

  • Fail: Won't go on, or slips freely around the head.

Summative: Wrench Presentation.

 

  • Rubric:

    1. Functionality: Evidence of a working print.

    2. Documentation: Blueprint included with correct dimensions.

    3. Reflection: Analysis of why the first print failed (or why it succeeded).

 

  • Hardware: 3D Printers (PLA filament).

  • Tools: Digital Calipers and a "Bucket of Bolts" (various sizes: M6, M8, M10, 1/4", 1/2", etc.).

  • Software: Fusion 360

  • Handout: "Wrench Design Brief" (listing the required handle length and thickness constraints).