Week 06: Computer-Controlled Machining

CNC Milling – OSB C-Table Prototype

For this week, I used the CNC router to fabricate a C-shaped side table out of OSB as a full-scale prototype.

Design Intent

I designed the table as a C-table that can slide partially under a couch, with a soft wave motif running through the profile. The waves were intentional - I wanted the piece to feel light and fluid despite being made from a relatively heavy, rough material like OSB. Before finalizing the dimensions, I measured my couch to make sure the height, depth, and clearance would work in a real domestic setting. This directly informed the final scale of the piece.

I ended up making two design versions:

• an initial version to test proportions and structural logic
• a refined version adjusted after reviewing the first cut and fit

This first CNC cut was very much treated as a prototype, not a final object.

Initial Concept & Sketch

Fusion 360 Design Process

Moving from sketch to 3D model in Fusion 360, considering material constraints, joinery, and CNC machining capabilities.

Manufacturing Workspace Images

Avid CNC Router – CAM + Machine Notes

CAM Setup (Fusion 360 / Manufacturing Workspace)

1. Switch to Manufacturing: Go to Manufacture workspace. This is where toolpaths and machine strategy are defined.
2. Arrange Parts: Use Arrange. Select the faces you want pointing up (important for how the machine cuts). Make sure parts are oriented the way the CNC expects them.
3. Define the Stock (Envelope): Tell Fusion what the stock/envelope is. This represents the physical OSB board size being milled.

New CAM Setup

1. Create New Setup: Select New Setup. Tell Fusion which parts/bodies you're machining. Enter stock measurements (length, width, thickness).
2. Coordinate System: Define the work coordinate system. Select axes manually. Flip the axis so it matches how the Avid CNC machine is oriented. Define where zero (origin) will be for the machine.

Tool + Cutting Parameters

1. Units: Speeds and feeds are set in inches.
2. Machine Strategy: Use 2D Contours for cutting profiles.
3. Tool Selection: 3/8 inch flat end mill.
4. Speeds and Feeds: XY feed rate: 120 inches per minute. Spindle speed: 12,000 RPM.
5. Geometry Selection: Select the bottom face of each part when defining contours. This ensures the cut goes fully through the material.
6. Tabs: Turn tabs ON to hold material in place during cutting. Tabs prevent parts from shifting or flying loose.

Layout + Toolpath Details

1. Arrangement Adjustments: Edit arrangement where necessary. Keep parts approximately 3 inches apart. Geometry preview shows cutting planes and direction.
2. Offsets + Passes: Offset: -0.03. Passes: default settings. Adjust linking parameters if needed for entry/exit moves.
3. Simulation: Always simulate toolpaths. Check for: collisions, correct cut depth, clean contours.

Post-Processing

1. Generate G-code: Post-process toolpaths. Use the Avid CNC–specific post processor. This creates the G-code file for the machine.

CNC Machining Process Documentation

Machine Controls (Avid CNC)

Feed Rate Override: Controls cutting speed while actively machining. Set to ~50% initially for safety. Can be adjusted in real time.

Rapid Rate: Controls how fast the machine moves when not cutting.

Jog Rate: Controls movement speed when jogging the machine using the keyboard.

Spindle Override: Controls spindle speed. Can be adjusted while running if needed.

Starting the Job

• Green button: Start job
• Yellow button: Feed hold (machine pauses but spindle stays on)
• Turn on Relay 1 for dust collection
• Double-check: spindle is plugged in, dust collection is on, material is secured

Post-Processing + Assembly

For this cut, I intentionally did not create tabs in the CAM setup. This was a conscious decision - I didn't want to overcomplicate the process on my first iteration and instead wanted to see how the design behaved when milled at full scale. The goal here was learning through making, not perfection.

The OSB board was milled successfully, and the overall geometry held up better than expected, especially along the curved wave edges.

I had to remove remaining material carefully after the cut. To do this, I used an oscillating saw (the type commonly used for removing casts) to cleanly separate and free the parts. There is a short video documenting this process, showing the removal and cleanup step.

Once the pieces were free, I assembled the table and tested it in context next to and partially under the couch. Seeing it in use was critical - it helped me evaluate:

• scale
• stability
• ergonomics
• and whether the wave language translated well into a functional object

This assembled piece will remain a working prototype, which I'm using to decide whether I want to:

• refine the joinery
• adjust thickness
• or further advance the wave geometry before committing to assembling the second version.

Final Assembled Table

Acknowledgements

Huge thanks to Anthony for staying back with me and helping me through this process out of schedule - especially with the CNC setup and decision-making along the way.

Also thank you to Jesse for helping me think through different ways the parts could be assembled and held together, which directly informed how I approached this prototype.