4.3. 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: Stanford OpenArm

Image: Planetary Gear by Rob Ives

Image: joinery example from Makezine

Image: basic pivot joint

Contents

• Tutorial: Mechanical Design using the Laser Cutter
  • Overview
  • Laser Considerations
  • Online Tutorials and Examples

4.3.1. Overview

This is a quick take on practical mechanical design techniques for machines we will fabricate using the laser cutters. First, some terminology:

Structures

• plate, gusset, I-beam
• truss
• interference fit (or press fit)
• free fit
• snap fit, tabs and slots

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

Mechanisms

• shaft
• actuator
• transmission
• linkage (four-bar linkage, diagram)
• bearings
  • plain bearing (sliding contact)
  • washers (sliding contact)
  • bushing (sliding contact)
  • ball bearing (rolling contact)
• shaft
  • shoulder screw (images)
  • rod stock
  • dowel pin
• clevis, pin, and tang

4.3.2. 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
• Dave Touretzky’s 15-294 Laser Cutter Intro

4.3.3. 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 Box Designer
• 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
• OpenArm 7-DOF robotics arm (from Stanford Salisbury Robotics Lab)
• Piccolo CNC-bot
• MicroSlice laser-cut laser cutter plans
• Universal Joint by Rob Hopeless