Personal and Group Assignment
This week’s personal assignment was to document the process of designing and machining a large-scale project. The group assignment focused on testing the machine's runout, alignment, speeds, feeds, and toolpath capabilities.
Group Assignment
Here’s also the link to our group assignment of this week.
What is Computer Controlled Machining?
It is a subtractive fabrication process where a computer-controlled cutting tool (a router bit) removes material from a solid block to create a shape. Unlike laser cutting, CNC machining allows for 2.5D and 3D shapes by controlling the depth (Z-axis).
CNC Tooling and Bits
Choosing the right tool is essential for a good finish and machine safety. These are the most common bits I used:
Pulls chips upward. Excellent for clearing material in deep cuts but can leave a rough finish on the top surface of the wood.
Pushes chips downward. It provides a very clean top surface finish, ideal for shallow engraving or thin materials.
Combines up-cut and down-cut geometry. It leaves a clean finish on both the top and bottom of the material, perfect for plywood.
Machine Specifications
Before machining, I reviewed the technical specifications of our machine to set the correct feeds and speeds in VCarve.
This is the large-format CNC machine at Fab Lab Puebla.
| FEATURE | CNC Router |
|---|---|
| Work Area | 1220 x 2440 mm (4' x 8') |
| Spindle Speed | Up to 18,000 - 24,000 RPM |
| Materials | Plywood, MDF, OSB, Foam, Soft metals |
| Hold-down | Vacuum table / Nails |
| Axis | X, Y, Z (3-Axis) |
| Post-Processor | G-Code (Arc/mm) |
CAM Process in VCarve
To convert my 2D design into machine instructions, I used VCarve Pro. This is the workflow I followed:
| STRATEGY | APPLICATION | PARAMETERS |
|---|---|---|
| Profile | Cutting out the external shapes | Outside vectors, add Tabs |
| Creating hollows or recesses | Inside vectors, clearing path | |
| Drilling | Pre-drilling holes for screws | Center of circles, Peck drilling |
| Dog-bones | Corner clearance for joints | Corner fillets for 90° fit |
Step by Step: VCarve Setup
We need to prepare our design for Cutting.
01. Opening file
02. Select measurements
03. Close all vectors
04. Calculate Routes
05. Edit revolutions
06. Run Simulation
07. Save Cutting File
Step by Step: CNC Setup
Operating a large machine requires a strict safety protocol.
01. Safety Gear
Always wear eye protection and ear muffs. Tie back long hair and avoid loose clothing.
02. Mount Material
Secure the plywood to the bed. Ensure no nails are in the path of the cutting bit.
03. Install Bit
Clean the collet, insert the bit, and tighten it securely using the wrenches.
04. Set Origins
Move the tool to the X and Y starting point. Use the Z-probe to find the material surface.
Step by Step: Mach3 Soft
Preparing the router.
01. Open the software
02. Open File Exported from VCarve
03. Set the Routers origin in the software.
04. Run Cutting Process
Fabrication and Assembly
Step 1: Machining
Running the G-Code. Monitoring the machine at all times.
Step 2: Sanding
Cleaning the edges and surfaces to remove burrs and splinters.
Step 3: Joint Check
- Press-fit: Testing the tolerance (0.1 - 0.2mm).
Step 4: Final Result
The assembled furniture piece, stable and without mechanical fasteners.
Downloadables
Here you can find the files to download