Week 17 – Wildcard Week

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Fab Academy – Week 17

Date range: 13 May - 19 May

Instructor: Neil Greshenfeld

🧠 Learning Objectives

  • Demonstrate workflows used in the chosen process
  • Select and apply suitable processes (and materials) to do your assignment.

📋 Assignments

Individual Assignment

  • Document the workflow(s) and process(es) you used
  • Explain how your process is not covered in other assignments
  • Describe problems encountered (if any) and how you fixed them
  • Include original design files and source code
  • Include ‘hero shot’ of the result

🛠️ Tools & Materials

  • Inkscape, OnShape
  • Laser cutter, 3D printing
  • Acrylic sheet and PLA

🧭 Introduction

This week we are asked to create our own assignment. I can admit that for my final project I tried to play it real safe, and work in spirals that I can handle given my work and busy life. But when this week came I started thinking of ways I can improve my final project and add some kind of complexity. Since my final project is all about calm and wellbeing, and since there’s a feature of guided breathing with lights, I wanted to make it look more alive when guiding me in a breathing session. So the challenge was how do I make my device breathe.

I started exploring and researching mechanical movements that look smooth and can resemble breathing.

I started looking into Iris mechanism (or Iris Diaphragm) and how it can be implemented, it’s the mechanism that opens and shut the camera lens.

https://upload.wikimedia.org/wikipedia/commons/4/48/Iris_Diaphragm.gif?_=20151027125422

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I also, thought about making cubes that move in and out following the same mechanism here, but this would require many servos, and they are not quite.

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Then I came across this clock, which was mesmerizing, it opens up and closes as time move, it was so smooth and natural that it almost felt alive:

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So I decided to give it a try. I found this tutorial on Grasshopper: https://www.youtube.com/watch?v=kdzE6yxsb44

🧪 Process & Workflow

  • Process Chosen: Digital Fabrication of a Mechanical Iris / Kinetic Solstice Mechanism.
  • The Goal: To scale up the LumaWell final project by adding smooth, mechanical movement to simulate a physical breathing cycle during guided wellness sessions.

Step 1 – Design (OnShape & Inkscape)

When I started designing the arms, I wasn’t sure what size to use. I looked at the ones on YouTube, took a screenshot, and roughly measured the angle.

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I designed it with an angle of 150 degrees

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I then designed the joints in two parts. I made 4 of them longer than the others because they are the ones responsible for anchoring the primary arms to the static acrylic back panel.

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The two halves of each joint are designed to hold together via a very tight mechanical press fit.

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Attempting to model the full concentric motion and assembly paths directly in OnShape proved harder and more constrained than expected, so I moved quickly to physical prototyping.

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Step 2 – Fabrication (Laser Cutting and 3D Printing)

I first cut the arms with the laser cutter and used a metal pins to hold the parts together to see if it’s actually going to work, and did, it was wobbly a bit but the mechanism was successful.

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Then I 3D printed the joints with 3D printer.

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As for the mechanical drive movement, I found an open-source linear gear actuator designed for the 28BYJ-48 stepper motor on printables.com, I printed it expecting to modify it, but surprisingly it worked perfectly out of the box, it even featured an end-pin that mapped directly to my mechanism's driver slot.

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Step 3 – Assembly

I started assembling the parts with the 3D printed jionts, then fixed them on the panel with the longer one.

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Next, I aligned and assembled the linear actuator mechanism.

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For this rapid prototype iteration, the motor housing is fixed to the back panel using a strong adhesive. For the next design spiral, I will modify the CAD to integrate a modular motor bracket that screws directly into the main panel.

Here's the final result in motion:

📝 Why This is a "Wildcard" (Not Covered Elsewhere)

  • This assignment explores Kinetic Linkage Assemblies and Mechanical Metamaterials (Iris/Solstice structures).
  • While previous weeks covered separate production methods (just 3D printing or just laser cutting), this week focuses entirely on the intersection of multi-material mechanical tolerances, overlapping moving joints, and dynamic physical movement to create an expressive interface.

⚠️ Problems & Solutions

  • Problem: The 3D printed joint pins ended up slightly smaller than the holes in the laser-cut acrylic arms. This introduced mechanical backlash, making the expansion movement a little bit out of sync (some segments lagged behind before the rest followed).
  • Fix: For the next iteration, I will increase the pin diameter by 0.15mm in OnShape to turn it into a true friction-fit, eliminating the slop between the links.

🧩 Files