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First step into machine building

Machine building study session #3, Aug 10, 2025

1. Kan-gineering

Kan-gineering (勘ジニアリング), a Japanese term used in manufacturing industry combining "kan" (intuition) and engineering, is making through experience, observation, trial and error. It’s a practical, hands-on approach that values doing over calculating. It has its pros and cons, but I believe it's still essential, especially when making (almost) anything.

2. Case study: 3D printed tripod

One of the essentials for Fab Academy documentation... is a tripod. This is a 3D printed phone tripod using various mechanisms, M5 bolts, insert nuts, and printing hacks. No more shaky LED blinking videos on repo!

Files and parts

  • Tripod_250809.3mf
    • Printable without support
    • Printing time: 2 ~ 2.5h
    • Filament: 35 ~ 45g
  • Fixture
    • M5 x 16mm Hex socket head cap bolt: 4
    • M5 nuts (Height: 4 ~ 4.4mm): 4

3. Design process

Balancing (mainly) 3 aspects:

  1. How it works
  2. How it's made
  3. How it interacts

A. How it works: Types of motion

  • Linear motion: Phone clamp using 3D printed threads
    • 9 mm diameter (Practically, the smallest threads for FDM 3D printing)
    • Chamfer is essential for ease of insertion
  • Rotary / Oscillating motion: Legs bending from 0° to 180° tightened by M5 bolts and nuts
  • Irregular motion: Ball joint for flexible clamp orientation

Strength

  • Compression and Tension
  • Stress-Strain Diagram
  • Second moment of area (aka second area moment, quadratic moment of area, area moment of inertia)

References (JP):

Every Kind of Bridge Explained in 15 Minutes

B. How it's made: Printing hacks / Nuts & bolts

3D printing... In theory, almost any form can be created, but there are limitations for better mechanical strength and printing neatly.

  • Printable without support: overhangs greater than 30° or small bridges
  • Insert nuts: hex dent with 0.1~ mm clearance
  • Strength for 3D printing:
    • Layer direction (compromised)
    • Inside corner radii to avoid stress concentrations

Bolts and nuts... Measure with a caliper

C. How it interacts: Human contact / Aesthetics

  • Safety / Ergonomics / Comfort: Outer corner radius, anti slip pattern (also as a message)
  • How it feels... Appearance / Aesthetics / Style
  • Basic forms + Corner radius / Chamfer
    • Sense of directionality
    • Corner radius: Tangent (G1) / Curvature (G2)

(Industrial) Product design

4. Assembly

Insert nuts

Assemble the ball joint

Tighten the legs with bolts

Also on Printables 😎