Computer-Controlled Cutting

A Brief History of CNC

Numerical control started with punch cards, computers just made it faster and more accessible. At its core, everything runs on G-code: instructions with X, Y, and Z coordinates, with the machine interpolating between those points to create paths.

How Laser Cutting Works

Fun fact: the first laser was essentially a microwave. Lasers (Light Amplification by Stimulated Emission of Radiation) used in digital fabrication are typically CO2 lasers. The system fires a focused laser beam through a nozzle onto the material surface. A smoke extraction system removes toxic fumes and a compressed air supply keeps things clean, because if smoke lingers, it overburns the material. And if you ever see a flame? Stop the machine immediately.

Laser Types & Materials

• CO2: Organic materials, high versatility
• Neodymium: Thinner materials
• Fibre: Thicker materials, easier to maintain

You can work with plastic, wood, cardboard, fabric, and more, but never metals, and materials should be max 8mm thick. Materials to absolutely avoid: PVC, carbon, chrome-tanned leather, PVB, beryllium oxide, and halogens, these release toxic gases. One interesting material: Delrin: self-healing and self-lubricating, perfect for gears.

Key Principles

• Power vs. Speed: You can either increase power or reduce speed. Finding the balance is everything.
• Lens clarity: If it's not cutting, check the lens first.
• Colour codes: Pure colours only! Red = inner cuts (cut first), Black = engraving, Blue = scoring.
• Cut order: Always inner cuts before outer cuts, material can shift once pieces are freed.
• Kerf: The laser removes a width of material. Test every material!
• Nesting: Arrange cutouts efficiently to save material.

The colour code system: blue (score), red (cut), black (engrave). Must be pure colours, never mixed.

Design Techniques

• Waffle/interlocking: Fusion 360 can slice a 3D model into stackable 2D pieces
• Living hinges (kerfing): Removing strips to allow bending
• Tessellation, folding, laminating: All possible with the right material knowledge

Wood with cross-directional grain is less brittle; acrylic is beautiful but unforgiving.

Step 0: Safety Training & Booking Test

Before operating the machines I took the lab's booking-system test, which doubles as the safety sign-off, after a tour of all four laser cutters. The non-negotiables drilled into us: only cut laser-safe materials (never PVC or certain foams; they release toxic fumes), keep ventilation, valves, and the exhaust fan running, always close the top lid before starting, run inside cuts first, and mask one side of reflective materials so the beam can't bounce off the internal mirrors. And always do a test cut first; the lab keeps test swatches for exactly this.

What the training actually changed for me was how I think about the machine. I'd quietly filed the laser cutter under "printer" load a file, press go. The safety session reframed it as something closer to an open flame on rails: the same beam that scores acrylic can set it alight, and the wrong material doesn't just fail, it releases gas that can hurt you and corrode the machine. The rule that stuck hardest was the dumbest-sounding one never walk away mid-cut because once I understood a flare-up happens in seconds, "watch the whole time" stopped being a chore and started being obvious. Booking access through a test you have to pass makes that point structural: you don't touch the machine until you've proven you know how it can go wrong.

Step 1: Prepare the File

Decide what's a cut (vector) vs. an engrave (raster). Assign pure colour codes; red for inner cuts, blue for scoring, black for engraving, and set cut lines to hairline width so the driver reads them as vectors, not rasters. Nest parts to save material.

Step 2: Load & Focus

Lay the material flat on the bed and set the nozzle height with the focusing gauge for that thickness (on the Rayjet 500 we focused with the laser height set to 0). If it isn't cutting, check focus and lens clarity first.

Step 3: Set Power, Speed & Test

Balance power vs. speed for the material, more power or less speed cuts deeper. New material with no spec sheet (hello, tortilla) means a test cut first to dial in settings, then record them.

Step 4: Cut Order & Run

Cut inner shapes before outer; material shifts once outer pieces are freed. Send to the machine driver, set the origin, and run with extraction on and the lid closed, watching the whole time.

Step 5: Weed, Account for Kerf & Assemble

Pop out the pieces. The laser removes a kerf of material, so slot fit depends on it; my "3mm" acrylic was really 3.18mm, and the kerf is exactly why the 3mm slot fit best. Factor kerf into joint clearance before trusting any fit.

Challenge 1: Material Prep

Copper tape is not an easy material. It peels off, creases easily, and the blade alignment has to be perfect. I learned to squeegee the tape flat first, then cut it to the exact width needed.

Squeegeeing copper tape flat, two strips side by side to give enough width for the intricate design

Challenge 2: Cutting Intricate Copper

My design was too detailed for a single strip, so I placed two strips of copper tape side by side to make the design larger and easier to cut.

Ready to cut: copper tape on the mat, floral design loaded in Silhouette Studio

Challenge 3: Non-Conductive Adhesive

The sticky side of copper tape isn't conductive. This meant I had to fold pieces together and carefully route the wiring. Solder bridges were needed to connect the circuit across the seam.

The Moment

Once the circuit was sorted, I found a model to pose with the hands and captured the moment: the LED lighting up when two fingers touch.

The divine spark: LED lights up when the copper-tape hands connect ✨

The Comedy of Errors

Step one of laser cutting: find the USB.

Then our first cut came out at the wrong scale, not 1:1. Once we fixed that, we could finally test the fit.

Testing & Results

"The 3mm slot was the best fit on '3mm' acrylic because the kerf removed just enough material to compensate for the actual 3.18mm thickness."

Step 1: Model & Slice

Modelled the cat head as an STL in Fusion 360, then used Fusion Slicer to generate the waffle pattern, 10 slices on the first axis and 9 on the second.

The cat head in Fusion 360: deliberately simple and abstract but immediately recognisable

All 10 pieces: X-slices (red) and Z-slices (blue). Finished size: 3.3" × 3.5" × 3.3"

Step 2: The "Hairline" Headache

I kept getting a "No jobs for transmission found" error from RayjetManager. After much frustration, I discovered that Rhino's RayJet driver is extremely finicky about line width ; it must be set to exactly hairline. Even half a pixel wider and it treats your vector as a raster.

The dreaded error, one pixel too wide and the machine ignores your entire design

Step 3: Cutting

Once I fixed the hairline issue, it was time to cut. Setting the nozzle height with the focusing tool is critical for a clean cut.

The laser cutter in action, cutting the cat head waffle pieces

Step 4: Assembly

Putting acrylic waffle pieces together is not for the faint of heart. The material is brittle, unforgiving, and has sharp edges; I cut my hand a few times. But the final result was worth it. For joint clearance I used the 3mm slot against the real 3.18mm acrylic; the kerf made up the difference for a snug friction fit with no glue.

The finished cat head; clear acrylic waffle structure, abstract but instantly recognisable ✨

Finding the Parameters

Tortillas don't come with a material spec sheet, so I ran multiple test cuts to dial in the settings. Different brands = different thicknesses = different settings. If you switch brands, re-test!

Laser cutting a tortilla

The Design

I'm designing an interlocking hexagonal pattern of circles that, when assembled, would create a waterproof custom burrito shell engraved with common flora found in Spain, a tribute to the country and one of its iconic foods.

Status: Work in Progress. The interlocking is tricky because laser-cut tortilla gets slightly charred and brittle at the edges, so the notches need to be thick enough to hold without snapping. The quest for the perfect fabricated burrito continues.