Day 3: (Mon Aug 31, Week 2) Laser-Cutter Structure Design

Notes for 2026-08-31.

New Assignments

New assignment, due Wed Sep 2: Exercise: Joyful Motion. Please be sure to bring your device to class on Wednesday.

Looking ahead, on Wednesday I will assign another device to design and fabricate for Wed Sep 9.

Administrative

1. Please remember we do not have class on Labor Day, Monday Sep 7.

2. IDeATe will be hosting two fire extinguisher training sessions on Wednesday September 2 at 10AM and 5PM in IDeATe Studio B, Hunt 106C. The 10AM session conflicts with our class time, but please let me know if the 5PM session would help you satisfy the laser cutter requirements.

   5:00PM session calendar link

3. Please test your ID card on the door lock. If it isn’t working, please both let me know and email help@ideate.cmu.edu

4. The first FriDeATe (social free food) event will be Friday, Sep 11 5-6PM in the basement open area.

Agenda

1. Brief review of results from Exercise: Joyful Form

2. New assignment Exercise: Joyful Motion

3. Any residual CAD or export questions?

4. Designing for laser-cut parts

   • review of kerf and tolerance

   • mortise and tenon connections (see Flat-Pack Joinery)

   • captive screws (see Design Example: Joinery)

   • dowels pins and friction fits (see Design Example: Joinery)

   • structural rigidity and constraint

   • stress concentrations

   • edge and corner safety

5. Kinematics

   • rigid-body mechanics

   • lower pairs (see https://en.wikipedia.org/wiki/Kinematic_pair)

   • practical joints

   • two-point shaft contact (hinges)

   • non-rigid joints

6. Transmission

   • 507 Mechanical Movements

   • wheels

   • gears (see Design Example: Gears)

   • linkages

   • shafts

   • cams (see Design Example: Cam-Action Tubing Clamp)

   • ratchets

   • clutches

   • timing belts

   • cables, tie rods

7. Human affordances

   • grasping

   • crank or dial

   • lever

   • string pull

   • buttons and releases

8. Fasteners

   • Lab Inventory: Fasteners

   • wood screws, machine screws and threaded holes, bolts and nuts

   • thread size and holes: clearance, tapping, and self-tapping

9. Time permitting: individual design consultation

Mechanism Samples

The external site 507 Mechanical Movements has an amazing array of mechanical structures for transmitting and transforming movement, including some which have been animated.

A few notable samples:

• spur gears: https://507movements.com/mm_024.html

• variable-rate gears: https://507movements.com/mm_038.html

• ratchet: https://507movements.com/mm_075.html

• intermittent motion gears (similar to Geneva mechanism): https://507movements.com/mm_068.html

• Geneva mechanism: https://507movements.com/mm_215.html

• cam and follower: https://507movements.com/mm_096.html

• quick return crank: https://507movements.com/mm_100.html

• “lazy tongs” linkage: https://507movements.com/mm_144.html

• pantograph linkage: https://507movements.com/mm_246.html

• parallelogram linkage: https://507movements.com/mm_325.html

• toggle joint: https://507movements.com/mm_140.html

• knee-lever toggle: https://507movements.com/mm_164.html

• chain and sprocket: https://507movements.com/mm_227.html

• toothed chain (similar to timing belt): https://507movements.com/mm_229.html