Making something BIG. Turning wooden sheets into a dog fortress!
This week's directive is to "Make Something Big" using the CNC Router. I decided to design and build a custom wooden house for my dog. The challenge? It must be assembled entirely using press-fit joints, meaning no glue, no nails, and no screws allowed!
Before cutting our final projects, the team tested the CNC router's runout, alignment, speeds, feeds, and toolpaths. We determined the exact tolerances needed for our press-fit joints in the plywood we are using.
Before jumping into CAD, I needed a concept. I wanted to design a dog house that wasn't just a boring traditional box, I wanted it to have personality and style. After sketching some ideas, I settled on a basic, geometric design without a door (My dog is a little fat jajajaja) so I could focus on the interlocking joints and the overall structure. I also wanted to make it modular, so I designed it in separate panels that could be easily cut and assembled.
To ensure the house is structurally sound and easy to assemble, I modeled every piece parametrically in SolidWorks. Based on our group assignment, I set my material thickness parameter to 12mm. To compensate for the machine's runout and the material, we determined a tolerance/clearance of 0.2 mm was needed in the slots. This ensures a tight press-fit joint without splitting the wood.
Because a round CNC bit cannot cut a perfectly sharp 90-degree internal corner, I applied a "dog-bone" technique on the inner corners. Using a 1/4 inch endmill, I created fillets with a radius slightly larger than 3.175mm. This ensures the interlocking pieces fit perfectly flush without manual filing.
The first critical step in VCarve is the Stock Setup. I measured my plywood sheet with digital calipers in multiple spots to confirm the true thickness. I set my X/Y Origin to the bottom-left corner and the Z-Zero to the top of the material surface.
I selected a 1/4 inch Flat Endmill. Based on our group assignment tests, I applied the following cutting data to avoid burning the wood or breaking the bit:
I divided the job into specific toolpaths:
Time for the heavy machinery! Before running any code, the stock must be completely rigid. We secured the large plywood board to the sacrificial CNC bed using wood screws around the outer edges and in the empty spaces between the pieces. I double-checked the toolpath simulation to make absolutely sure the router bit would never crash into a metal screw.
Operating the CNC requires a strict calibration protocol:
After the CNC finished, the manual labor started. Removing tabs, sanding every edge to prevent splinters, assembling the press-fit structure, and applying varnish to protect the dog fortress from the weather. Here is the full process compiled:
The dog fortress is complete! The structure is incredibly rigid thanks to the tight tolerances of the press-fit joints, and most importantly, the client approves of the final result.
Week 7 is complete. The transition from digital CAD to a massive physical object using the CNC router was a success.