CNC basic principle illustration

Computer-Controlled Machining

Format: Lecture.

Learning Outcomes:

Students will be able to successfully

  • Demonstrate understanding of the risks involved with CNC milling and how to mitigate them.
  • Use a 2d or 3d design to mill out a 1 or 2 part mold.
  • Choose between different materials and tools depending on the part that is being created.
  • Create different toolpaths for both 2(1/2)D and 3D milling processes.

Introduction:

  1. What can be made with CNC milling?
  2. Flextures, live hinges
  3. Size and scaling (going from laser to mill)
  4. Cool projects
    • Opendesk
    • FabHouse
    • Shelter 2.0 / Wikihouse
    • 10,000 Year Clock

Safety

TOOLS SPINNING AT HIGH SPEED CAN SHATTER OR START A FIRE! NEVER REACH INTO A RUNNING TOOL

  • Risks involved with CNC milling
  • Holding down material clamping, fixtures
  • Using tools, keeping them in good shape
  • Safety gear, space and working together
  • Dust and dust collection

Machines

  • Shopbot, Roland, others

Materials

  • Wood and derivatives
  • Plastics
  • Foam
  • Machinable wax
  • Aluminium

Files Formats

  • 2D: SVG, DXF
  • 3D: STL, STEP
  • Shopbot .sbt
  • Roland .rml

Speeds and feeds

  • Chip load
  • Feed speed calculations
  • Cut depth
  • Step over
  • Direction
  • Optimization
  • High speed machining

Tools and Tooling

  • drill bits vs end mills
  • flutes
  • coatings
  • center-cutting
  • up/down cut
  • flat/ball end

Toolpaths

  • kerf, offset, runout
  • conventional, climb
  • 2, 2.5, 3, 4, 3+2, 5
  • rough/finish cuts
  • cut depth, clearance, collisions
  • t-bones
  • tabs
  • ramping and lead-in, -out
  • test cuts, cutting air

Assignment

Design and mill a 1 part 3D mold or a 2 part 2-1/2 or 3D mold. Document how you chose the material, tools and toolpaths used and if you would change anything if you would to it again - i.e. what did you learn from your choices?

Resources for self study

Example grid:

A grid showing three main milling bit geometries applied to common toolpath types:

Example grid for CNC milling techniques

Download example grid source files here.

Notes

Make clear what is bonus learning, what is required learning

Backup homework in case of no milling access: gather data from hand drilling various materials and make online simulation.

Make curriculum work as introduction milling in general fab lab use.

How to mention complexity VS potential? CNC milling has the most capabilities of all the fab lab tools, yet it is the most under utilized technique. Large options of choice (miling bit size, milling bit geometry, materlials, 2D and 3D cpabilities) makes it diifuclt to make simple software and interfaces.

Main intro is meat, showing the principles of milling. chapters following that show how to do the same type of cutting in different software.

Make separete chapters for different software.

Bonus chapters show how to set up the different softwares.

Toolpath software to make guide for:

  • V-carve
  • Fab modules
  • FreeCAD?
  • Bark beetle for Rhino?
  • Fusion 360?
  • Fabacm.cc?

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