In this unit students will be introduced to Computer Numerical Control (CNC) machining with the culminating project involving students writing a CAM file in g-code that is used to produce a custom wooden maze. During this unit the following concepts/topics are discussed:

• CNC machining
• Machining
• Demand for CNC machinists
• CAD vs. CAM
• Common CNC software
• Cartesian coordinate system
• Ordered pairs
• G-code
  • Block number
  • Preparatory function
  • Coordinates
  • Feed rate
  • Spindle speed
  • Tool number
  • Miscellaneous function
  • Common g-code commands (GOO, G01, G02, G03, G20, G21, ect.)

Included in this unit are the following materials:

• 24-slide Introduction to CNC Machining presentation
• Introduction to CNC Machining guided notes
• Coordinate system practice problems
• G-code practice problems (four total)
• G-code maze project instructions and rubric
• G-code maze template (two versions)
• 5x5 Maze design template (.pdf and .dwg versions provided)

When teaching this unit I recommend starting with the provided presentation while students take guided notes (provided). Students should then work through the Coordinate System Practice and G-Code Practice Problems worksheets. After completing these assignments, introduce students to the G-Code Maze Project and have them design their maze with the provided Maze design template. (Note that I created this template with the origin at coordinates 1,1 as I had to offset the stock from my machine’s 0,0 origin as the Carvey CNC machine I use has a clamp at this location.)

After students have completed their template, provide them with the G-code maze template file and have them create their maze in g-code (Note that two versions are provided, but it's possible that neither works correctly and you may have to slightly modify the program to work with your specific CNC machine). When placing the 5x5 stock in the CNC machine and running the file, take extra care as incorrect g-code or setup can damage the machine. The exact process and requirements will vary depending on the CNC machine you are using. 

I have been doing this project for over 6 years on two different CNC machines with great success and only some minor damage to clamps.

In order to complete the G-Code Maze Project, students will need the following equipment/material:

• CNC machine (the instructions reference Carvey made by Inventables, but other CNC machine should work)
• CNC software for running the g-code files
• ⅛” endmill bit
• 1/16” to ⅛” thick Acrylic cut to 5” x 5” squares (one per student)
• ½” to ¾” hardwood or MDF cut to 5” x 5” squares (one per student)
• ½” panhead screws (four per student)
• Bearing ball smaller than .125” (one per student to place in maze)
• Drill or drill press for pre-drilling acrylic and wood block holes

Please note that the exact process and requirements will vary depending on the CNC machine you are using. The holes drilled in the acrylic should be larger than the screw thread diameter. The pilot holes for the wood blocks should be slightly smaller. A rubric for the final project is provided.