CAM Machining

Assignment: Make Something Big

For week 7's assignment, we needed to make something big (~meter-scale) using computer-controlled machining. I decided to design and build a midcentury modern-inspired shelf using the ShopBot CNC router.

Inspiration: The $1000 Shelf

I recently found this really cute midcentury modern shelf on Wayfair that I absolutely loved. The problem? It was over $1,000! The design featured these beautiful curved sides that kind of look like candy canes, and I thought—why not just make it myself with the ShopBot?

Not only would I save a ton of money, but I'd also get to practice CAM toolpath generation and learn about large-scale CNC machining. Plus, I needed a shoe rack anyway! 👟

CAD Design in Fusion 360

Modeling the Candy Cane Sides

I started by recreating the shelf design in Fusion 360. The key feature was the curved "candy cane" shaped sides. I used spline curves to match the organic, flowing shape of the original design, then extruded them to the appropriate thickness.

Design Considerations

• Material thickness: Designed for 3/4" (19mm) OSB sheet stock
• Shelf dimensions: ~36" tall × 24" wide (meter-scale requirement)
• Number of shelves: 3 horizontal shelves for shoe storage
• Joinery: Glue and screws for assembly
• Curved features: Organic curves on side panels for aesthetic appeal

CAM Toolpath Generation

Setup in Fusion 360 CAM

After completing the 3D model, I switched to the Manufacturing workspace in Fusion 360 to generate toolpaths for the ShopBot.

Stock Setup

• Material: OSB (Oriented Strand Board) - 3/4" thick
• Stock size: 48" × 96" (standard 4×8 sheet)
• Origin: Lower left corner, top of stock

Toolpath Strategy

I created multiple toolpath operations to cut out all the parts:

1. 2D Pocket (for pilot holes and features)

• Tool: 1/4" flat end mill
• Operation: Create pilot holes and any recessed features
• Depth: Through-thickness where needed
• Stepdown: 0.125" per pass
• Stepover: 50% of tool diameter (0.125")

2. 2D Contour (for outlines)

• Tool: 1/4" flat end mill
• Operation: Cut part outlines including curves
• Depth: Full thickness (0.75") plus 0.05" into spoilboard
• Tabs: 0.25" thick × 1" wide, 4 tabs per part
• Lead-in/out: Smooth entry to prevent tool marks

Speeds and Feeds

I calculated appropriate cutting parameters for OSB:

• Spindle speed: 18,000 RPM
• Feed rate: 100 inches/min
• Plunge rate: 30 inches/min
• Chip load: ~0.014" (calculated: 100 IPM / (18000 RPM × 2 flutes) ≈ 0.003")

Layout and Nesting

I arranged all parts efficiently on the sheet to minimize material waste:

• 2 curved side panels (candy cane shape)
• 3 horizontal shelf boards
• 1 top piece
• Total material usage: ~70% of the 4×8 sheet

CNC Machining on the ShopBot

Machine Setup

Before cutting, I prepared the ShopBot:

1. Placed OSB sheet on the spoilboard and squared it to machine axes
2. Screwed down the sheet at corners and edges (avoiding toolpaths)
3. Zeroed X and Y at lower-left corner of stock
4. Zeroed Z on top surface of material using touch-off plate
5. Loaded 1/4" 2-flute straight end mill
6. Turned on dust collection system

Cutting Process

The cutting process took about 45 minutes total:

• Pocket operations: ~15 minutes for all slots
• Contour cuts: ~30 minutes for all outlines
• Manual tab cutting: Used oscillating saw to cut holding tabs after machining

Assembly

Putting It Together

After cutting all the parts and removing the holding tabs, assembly was straightforward:

1. Sanded all edges lightly to remove splinters (OSB is really splintery!)
2. Pre-drilled pilot holes using the CNC-milled guide holes
3. Applied wood glue to all joining surfaces
4. Assembled shelf boards between the side panels
5. Secured everything with screws driven through the pilot holes
6. Clamped the assembly while glue dried

Finished Shelf

I'm now using the shelf as a shoe rack, and it works perfectly! The curved "candy cane" sides give it that midcentury modern aesthetic I wanted, and the glued and screwed joints make it rock-solid.

Reflections & Lessons Learned

What I'd Do Differently

What Worked Well

• CAM toolpaths: Fusion 360's CAM workspace made it easy to generate efficient toolpaths
• Pilot holes: CNC-milled pilot holes made screw placement precise and prevented splitting
• Glue and screws: Strong, permanent assembly that can support weight
• Curved features: CNC made the complex "candy cane" curves effortless
• Cost savings: Total material cost ~$30 vs. $1000+ for the original!

Design Improvements

If I were to make this again, I would:

• Use Baltic birch instead of OSB for a better surface finish
• Add a back panel for additional stability
• Include adjustable shelf heights using a series of slots
• Round over the edges with a roundover bit for safety and aesthetics
• Apply a finish (polyurethane or wax) to protect the wood

Extra Credit

Conclusion

This project taught me the complete workflow of large-scale CNC machining—from CAD design and CAM toolpath generation to machine setup and assembly. While I learned that material choice matters a lot (seriously, OSB splinters are no joke), I'm really happy with how the shelf turned out. It serves its purpose as a shoe rack, looks great with those midcentury modern curves, and I saved nearly $1000 in the process!

Most importantly, this assignment showed me the power of computer-controlled machining for creating furniture and large-scale objects with complex geometries that would be extremely difficult or impossible to make by hand.