7.3. Tutorial: Mechanical Design using the Laser Cutter¶
These notes are meant to accompany an in-class tutorial presentation, and may not necessarily stand alone. For general reference, see also Mechanical Behavior.
Image: Planetary Gear by Rob Ives
Image: joinery example from Makezine
Image from Laser-Cuttable Flat-Pack Mechanical Design Kit under development
Contents
7.3.1. Overview¶
This is a quick take on practical mechanical design techniques for machines we will fabricate using the laser cutters.
kinematics: | the properties of movement |
---|---|
structure: | the rigid parts |
mechanism: | the moving parts |
actuation: | the sources of mechanical energy |
7.3.1.1. Kinematics¶
- degree of freedom (DOF)
- joint
- hinge or pivot (rotational joint, 1 DOF)
- translational joint (linear joint, 1 DOF)
- universal joint (two pivots, 2 DOF)
- ball joint (spherical joint, 3 DOF)
- flexure
- conservation of energy
7.3.1.2. Structure¶
- joinery, Flat-Pack Joinery
- plate, gusset, I-beam
- truss
- interference fit (or press fit)
- free fit
- snap fit, tabs and slots
- fasteners
- the bane of tolerance
7.3.1.3. Mechanism¶
- joints
- bearings
- plain bearing (sliding contact)
- washers (sliding contact)
- bushing (sliding contact)
- ball bearing (rolling contact)
- transmissions
- linkages
- four-bar diagram
- four-bar linkage
- laser-cut links
- hard wire links
- shafts
- shoulder screw (images)
- rod stock
- dowel pin
- shaft clamps
- heuristic: always support a shaft at two widely spaced points
- clevis, pin, and tang
- gears
- timing belts
7.3.1.4. Actuation¶
- descending weight
- clock spring
- flywheel
- hobby servo
- DC motor
- stepper motor
- DC motor linear actuator
- servomotor
- pneumatic cylinder
7.3.2. Laser Considerations¶
- choosing a 2D or 3D drawing program with DXF output in millimeters
- flat stock
- designing in layers
- designing with right angles
- joinery to create 3D from 2D parts
- kerf
- sharp inside corners
- tolerance and precision
- materials
- acrylic
- cardboard
- thin plywood
- paper
- fabric, leather, Delrin (acetal)
- fasteners (screw, nut, bolt)
- adhesives
- https://resources.ideate.cmu.edu/equipment/laser-cutter/
- Dave Touretzky’s 15-294 Laser Cutter Intro
7.3.3. FlatPack Kit¶
The course includes a lot of materials in the Laser-Cuttable Flat-Pack Mechanical Design Kit (under development).
7.3.4. Online Tutorials and Examples¶
There is so much great material online related to basic laser cutting technique that I won’t attempt to replicate it here, instead I’ll link to other sources:
- Make magazine joinery tutorial
- online gear template generator
- online Spur Gear Designer
- 50 Digital Joints (mostly for 3-axis CNC, some for laser) (alternate link)(alternate link)(alternate link)
- planetary gears and other mechanisms by Rob Ives
- Piccolo CNC-bot
- MicroSlice laser-cut laser cutter plans
- Universal Joint by Rob Hopeless
- Curved/Bending hard materials with Laser Cutter
- Google Books: 507 Mechanical Movements
- Google Books: The Engineer’s Sketch-book of Mechanical Movements, Devices, Appliances, Contrivances, and Details