LASER CUTTING & ENGRAVING

The complete workshop poster — beam physics · machine anatomy · safety · materials · LightBurn settings · calibration · troubleshooting
455 nm / 10.6 µmBlue diode · CO₂
0.1–0.3 mmKerf & spot size
300 × 300 mmTypical bed (A6 Pro)
up to 15 000 mm/minEngrave speeds
Class 1 / 4Enclosed / open

01🔦HOW A LASER CUTTER WORKS

LASER = Light Amplification by Stimulated Emission of Radiation — a single-colour (monochromatic), coherent, focused beam of light.

  • Generate: a diode (455 nm blue) or gas tube (CO₂, 10.6 µm) emits an intense beam of one wavelength.
  • Focus: the beam is collimated then squeezed by a lens down to a tiny spot → power density explodes (W/mm²), heating material to vaporisation / melting point.
  • Cut = moving the focused spot along a path, vaporising material (CNC gantry + steppers, GRBL firmware).
  • Engrave = same beam at lower power, scanning the surface to remove only a thin layer (raster).
  • Kerf: the width of material removed by the beam (0.1–0.3 mm) — designs must compensate for it.
  • Air assist blows vapor & smoke away → cleaner edges, less char, fewer flames.
  • Speed ↔ power trade-off: too fast = no cut-through; too slow = charred edges. Find the balance with test grids.
  • Focus position matters: best cut happens at the focal point — use the focus tool / z-height every job.
Laser source DIODE / CO₂ MIRROR LENS Focal point — spot 0.1–0.3 mm Workpiece (material) — vaporised along the cut path · kerf = removed width Air assist blows vapor away ↓

02⚗️LASER TYPES — WHAT & WHY

Typeλ / PowerCuts & marks
CO₂ gas10.6 µm · 40–150 WWood, acrylic incl. clear, glass, leather, paper, fabric, stone marking. The workshop classic — clean edges on acrylic.
Blue diode 455 nm1.5–20 WWood (thin), dark cast acrylic, leather, paper, anodised Al marking. Cheap, compact, air-cooled. Cannot cut clear/transparent or bare metal.
IR diode 1064 nm~1 W headMetal marking (steel, Ti) on coated / sprayed surfaces. Optional head for diode machines (e.g. DAJA A6 Pro).
Fiber / DPSS 1064 nm20–100 W+Industrial metal cutting & deep engraving (brass, steel, Al).
  • Why wavelength matters: CO₂'s 10.6 µm is absorbed by organics & acrylics (even clear). 455 nm blue passes straight through clear materials but is absorbed by dark pigments. 1064 nm IR is absorbed by metals.
  • Household / school / hobby machines are overwhelmingly diode or small CO₂. "20 W" marketing ≈ 5.5–20 W real output depending on brand — always trust test cuts, not the label.

03⚙️MACHINE ANATOMY (DIODE / GRBL)

ENCLOSURE — Class 1 when lid closed X/Y gantry rail LASER MODULE diode + collimator + lens beam ↓ Workpiece — taped flat, focus tool set Honeycomb / slat bed — lets beam pass, holds parts Exhaust fan + duct → outside FUMES CONTROLLER GRBL · G-code · USB
  • Steppers + belts move the gantry; GRBL reads G-code that LightBurn generates from your vectors.
  • Safety hardware: lid-open switch (kills beam), E-stop button, tilt sensor — never bypass them.
  • Lens & mirrors need cleaning — smoke residue slowly dims the beam (isopropyl + lens paper).

04🧯SAFETY — READ THIS FIRST

  • EYES Never stare into the beam. 455 nm blue is visible and can blind instantly; CO₂ 10.6 µm is invisible — silent damage. Enclosed machine = Class 1 (safe with lid shut). Open machines = Class 4 — wear laser goggles rated for the wavelength (OD ≥ 4).
  • FIRE Laser + wood = real fire risk. Never run unattended. Keep a fire extinguisher nearby; watch for sustained flame or heavy smoke on thick cuts and hit E-stop.
  • FUMES Always run the exhaust. Burning plastics (PVC, ABS) release toxic gases — only laser-safe materials, see panel 10.
  • HOT Freshly cut parts are hot — wait for them to cool, use gloves. Engraved edges can be sharp.
  • MACHINE Keep the lid closed while running; keep the work area clear of flammable clutter; never defeat the lid switch.
  • POWER Don't run the diode at > 90 % power for long jobs — it extends lens & diode life.
  • SETUP Focus with the focus tool before every job; ensure the material is flat and taped down.
Golden rule: if you don't know exactly what the material is — don't laser it. Test a corner scrap first.

05🧱MATERIALS MATRIX — WHAT LASERS CAN DO

MaterialCutEngraveBlue diode 455 nm notes
Plywood / basswood✓✓Best all-rounder. 3 mm easy; ≥6 mm needs 2–3 passes. Watch veneer char.
Hardwood (oak, walnut)⚠✓✓Engraves beautifully; cuts slowly on diode (resins). Great on CO₂.
MDF✓✓Clean cut, dusty; edges darken. Vent well.
Balsa✓✓✓Easiest wood — very fast cuts, low power.
Acrylic — dark cast✓✓Cut cast only; flame-polished edges. Keep protective film on.
Acrylic — clear / extruded✗✗455 nm passes straight through; extruded melts ugly. CO₂ handles both.
Leather (real / PU)✓✓Fumes smell — vent. PVC pleather = banned (chlorine gas).
Glass✗with prepNeeds black paint / colour sheet / wet-towel backing, then engrave.
Anodised aluminium✗✓✓Instant crisp white mark (~15 000 mm/min @ 90 %). Bare metal bounces the beam.
Stainless / brass / copper✗sprayOnly with marking spray/paste or 1064 nm IR head; multiple passes.
Stone / ceramic tile✗✓ CO₂Diode marks poorly; CO₂ engraves well.
Paper / cardboard✓✓Low power, fast — fire risk if too slow. Great for prototypes.
Fabric (cotton, wool)✓✓Seals edges. Synthetics melt — avoid.
Cork✓✓Easy, smells toasted.

Key: ✓ yes · ⚠ difficult/conditional · ✗ no. CO₂ machines are more capable on transparent materials & stone; blue diodes are pigment-hungry.

06🎛️SETTINGS CHEAT SHEET (20 W-CLASS BLUE DIODE)

STARTING POINTS, not gospel. Real output varies 2–3× between machines — always run the test grid (panel 09) and save winners to the Material Library.

MaterialCut speed (100 % P)PassesEngrave P / speed
3 mm plywood400–800 mm/min1–230–60 % · 3000–6000
6 mm plywood200–400 mm/min2–330–60 % · 3000–6000
3 mm basswood / balsa800–1200 mm/min125–50 % · 4000–8000
2–3 mm MDF500–900 mm/min1–230–55 % · 3000–6000
3 mm dark cast acrylic150–300 mm/min1–220–40 % · 2000–5000
Leather 2–3 mm300–600 mm/min120–40 % · 3000–6000
Anodised Al (mark)——90 % · ~15 000 mm/min
Cardboard 2 mm1000–2000 mm/min120–40 % · 5000–10000
  • Cut: full power + speed tuning beats slow single passes. Add passes for thickness.
  • Engrave: constant power (Max P = Power) for solid fills; lower Max P for shading/photos.
  • Air assist ON for cuts — cleaner, less char, fewer flames.
  • LightBurn: Material Library → New from Layer saves the winning layer as a reusable preset.

07🖥️LIGHTBURN WORKFLOW

  • 31 output layers (0–30) — colour = layer = cut parameters. T1/T2 are TOOL layers: never fire, no parameters — use for guides, material frame, notes.
  • Line mode = cut vectors (speed, power, passes). Scan mode = engrave fills (line interval / density). Image mode = photos (dithering: Jarvis or Atkinson for cleanest results).
  • Max Power = Power gives constant-power output (right for cuts). Lowering Max Power enables dynamic shading for grayscale engraving.
  • Tabs hold parts in place: auto width ≈ 1.5–2 × material thickness (5–8 mm for 3 mm ply), spacing 30–50 mm. Tab Cut Power 0 % = bridge stays solid; >0 % = pulsed score.
  • File prep: import SVG/DXF, check scale (mm!), strokes → hairline (0.001 mm) so vectors cut rather than fill, assign colours to layers.
  • Preview first: the simulation shows order + estimated time. Then Frame the job to confirm it fits on the material.
  • Offset tool applies kerf compensation (offset outside cut path by kerf/2) for press-fit parts.
Routine: import → scale check → layer colours → Material Library settings → Preview → Frame → exhaust on → run supervised.

08📐DESIGN & JOINERY FOR LASER

  • Kerf compensation: beam removes 0.1–0.3 mm — a "3 mm" slot is really ~2.8 mm. Offset cut lines by kerf/2 for press-fit joints.
  • Box joints / finger joints: tab width ≈ material thickness × 1 (e.g. 3 mm fingers on 3 mm ply); subtract kerf from every slot. Tolerances: laser = ±0.1 mm, much tighter than hand tools.
  • Tabs on nested parts stop cut-out pieces drifting into the beam path mid-job.
  • Engrave first, cut last — if the part moves, the engrave is already done. One file, two layers: Scan layer then Line layer.
  • Images: use 300 dpi+, high contrast, convert to grayscale; dither with Jarvis/Atkinson for photos.
  • Text: outline/convert text to curves before cutting (font substitution breaks files); keep cut text ≥ 10 pt.
  • Score lines: low-power Line pass (fold lines, bend points) — cut only partway through.
  • Nesting: pack parts tightly (shared edges save 10–30 % material) and share a single outer cut.
  • Inkscape / Fusion 360 / Onshape all export SVG/DXF; LightBurn imports them directly.

09🎯CALIBRATION TEST GRID — ALWAYS

Every new material or new roll/board = new test. Speeds on the internet vary 2–3× — your machine decides.

ENGRAVE — 10 × 10 grid

  • 10 squares × 10 rows: power 10 → 100 %, speed ladder 0.08 interval.
  • Pick the darkest clean fill at acceptable speed.

CUT — 6-line ladder

  • 6 lines at 100 % power: e.g. 1200 · 900 · 700 · 500 · 350 · 250 mm/min.
  • Push the pieces apart — first line that drops through cleanly = winner.
Judge by: full clean cut · minimal char · crisp edge detail. Then LightBurn → Material Library → New from Layer to save the preset with a name like "3mm ply — cut".

Re-test after: changing focus distance, cleaning the lens, or buying a new sheet (thickness/glue vary by batch).

10☠️BANNED MATERIALS — NEVER LASER

MaterialWhy it's banned
PVC / vinyl / pleatherChlorine gas — toxic to you, corrodes the machine's optics. Ruins the laser.
ABS / polycarbonate (Lexan)Melts, catches fire, releases toxic fumes.
Fiberglass / carbon fibreEpoxy/resin fumes are toxic; fibres irritate.
HDPE / milk jugsMelts, drips, floats up into the lens and fires.
Polystyrene foamMelts and burns almost instantly.
Bare copper / brass / mirrorsReflect 455 nm — beam bounce can hit eyes or the machine.
Unknown materialsIf you don't know what it is — test a corner scrap first or skip.
Wet materialsSteam can pop/shatter surfaces (esp. wood & glass).

Check adhesive/backing too — some "laser-safe" sheets have PVC-based glue or HTV backing. Read the SDS.

11✅STEP-BY-STEP WORKFLOW

  1. Design in LightBurn, Inkscape or Fusion 360 — SVG/DXF, mm units, kerf applied.
  2. Prep the bed — clean honeycomb, place material flat, tape down edges.
  3. Focus with the focus tool (or set z-height) — the #1 cause of bad cuts.
  4. Import the file, check scale, assign stroke colours → layers.
  5. Pick settings from the Material Library or a fresh test grid.
  6. Preview the simulation — confirm order, time, and that it fits.
  7. Frame the job — the laser traces the bounding box on the material.
  8. Enable exhaust + air assist. Check the fire extinguisher is close.
  9. Test cut a corner scrap first on a new material/settings.
  10. Run and supervise — watch for flames/smoke, E-stop if worried.
  11. Cool & remove — parts are hot; lift with tweezers/gloves.
  12. Post-process — peel film, sand edges, clean with isopropyl, assemble.

12🩺TROUBLESHOOTING

SymptomCauseFix
Not cutting throughToo fast · low power · out of focusSlow down, add passes, refocus
Charred / black edgesToo slow · too much power · no air assistSpeed up, cut power, turn air on
Uneven cut depthMaterial not flat · focus offTape down, refocus, shim
Engrave too lightLow power · too fast · wrong focusRaise power, slow down, refocus
Acrylic melted & uglyExtruded (not cast) · no air assistUse cast acrylic + air assist
White / blurry engraveFocus too high above surfaceLower z / refocus
Machine skips / jerksAcceleration too highReduce speed/accel in LightBurn
Smoke in roomExhaust blocked / offCheck duct & fan, vent outside
Beam getting weakerLens/mirror coated with residueClean with isopropyl + lens paper

Still stuck? Test grid beats guessing — one 5-minute test saves an hour of failed parts.