3D Engraving: STL & Grayscale on Wood, Metal, More

Beyond metal coin relief: the same depth-map principle applied to wood, acrylic, leather, stone, and coated tumblers. Source from STL or grayscale, optimize, engrave on either fiber (3D Sliced mode for metal) or CO2 (grayscale mode for organics).

Two source paths to the same depth map

You need a grayscale image where pixel brightness = engrave depth. White = highest, black = deepest (or the opposite if "Negative" is checked). Two common paths:

• STL → depth render (best fidelity). Build / sculpt in 3D, render the depth pass, save as PNG. The "what you see is what you carve" path.
• Image → AI depth map (fastest). Generate or scan a 2D image, run through SculptOK, MiDaS, or Marigold to estimate depth. Lower fidelity, but no 3D modeling skill required (covered in the Relief Coin module).

STL → depth map workflow

Option 1: Blender (free, full control)

1. Import or model your STL in Blender.
2. Add an orthographic camera looking straight down at the design.
3. In the Compositor (or just render passes), enable the Z (Depth) pass.
4. Render. The depth pass is a grayscale image where bright = close to camera, dark = far.
5. Map / Normalize the depth pass to fit pure black (deepest) ↔ pure white (highest).
6. Export as PNG at your final engrave dimensions.

Blender tutorial-search: "depth pass render Blender." Many YouTube walkthroughs covering this in 5-10 minutes.

Option 2: Aspire / Carveco (paid CAM software)

Built specifically for CNC + laser relief work. Import STL, set engrave dimensions, export as a depth map (often called "height map" or "lithophane mode" in these tools).

• Aspire (Vectric), industry standard for CNC, $2,000+. Excellent depth map export.
• Carveco Maker: subscription-based, $15/month, beginner-friendly STL → depth.
• Image2Surface (free Blender add-on), converts STL or scanned data to height maps.

Option 3: Z-Brush / Fusion 360

Both can export depth renders. Z-Brush has a "Best Preview Render" mode with depth output. Fusion 360 doesn't have a direct depth pass, but you can render an orthographic top view at high contrast lighting that approximates one.

Optimization checklist (before engraving)

Even a perfect STL needs prep before it engraves cleanly:

1. Resolution: aim for 600+ DPI at the final engrave size. A 100×100mm wood plaque needs ~2400×2400 pixels minimum. Lower DPI = jagged depth steps visible in the engrave.
2. Tonal stretch: Photoshop / GIMP / Affinity → Levels → drag the black point and white point sliders to anchor pure 0 and pure 255. If the depth map only uses the middle 50% of the gray range, you'll lose half your potential depth.
3. Gaussian blur: 1-2 pixel blur kills posterization at depth layer boundaries. Looks the same; engraves smoother.
4. Background cleanup: use a clean cutout (transparent or pure black) for areas that should NOT engrave.
5. Scale check: verify the image dimensions match your final part. A scale error on a wood plaque means you engrave a 90mm design on an 80mm board.
6. Negative test: if the depth map looks "inside out" engraved (subject sunken, background raised), check the Negative Image checkbox on the Lightburn image layer, flips white/black interpretation.

Wood: the headline use case

Wood + 3D engraving is CO2 territory primarily. Fiber lasers don't engrave bare wood well (1064nm wavelength reflects off most wood surfaces). On a quality CO2 (especially RF metal tube), wood relief looks stunning, burned topography that reads like a hand-carved bas-relief.

Best wood species

• Maple: light tone, even grain, takes contrast beautifully. Top choice for relief portraits.
• Cherry: warm tone, fine grain, deepens with age. Premium choice.
• Walnut: dark, rich, less contrast. Use for designs where dark engrave is acceptable as part of the look.
• Birch plywood: cheap, even, predictable. Best for prototyping.
• MDF: engraves consistently but no grain character. Functional, not premium.

Avoid: heavily grained woods like oak (the grain dominates the engrave); pine (resin pockets cause inconsistent burn); pressure-treated lumber (toxic fumes).

CO2 settings: wood relief (40-50W RF tube, 2" lens)

Wood	Speed	Power	Line interval	Image mode
Maple (4mm)	350 mm/s	25-35%	0.06 mm	Grayscale
Cherry (4mm)	300 mm/s	28-38%	0.06 mm	Grayscale
Walnut (4mm)	250 mm/s	35-45%	0.06 mm	Grayscale
Birch ply (3mm)	400 mm/s	22-30%	0.08 mm	Grayscale
MDF (6mm)	300 mm/s	30-40%	0.06 mm	Grayscale

Use Lightburn's Grayscale image mode (not 3D Sliced, 3D Sliced is the galvo equivalent). Power Min ↔ Power Max modulates per pixel.

Multi-pass approach for deeper relief

Single-pass grayscale on wood gives subtle relief (~0.5-1mm). For dramatic 2-4mm depth:

1. Run the grayscale image at standard settings, first pass.
2. Reduce Power Max by 5-10%, run again. Each pass deepens highlights, leaves dark areas alone.
3. Repeat 3-5 times for ~2-4mm total depth.
4. Optional final pass: invert the image (Negative Image checkbox) and run at low power to "burnish" the surface, adds character/weathering.

Wood prep & finish

• Mask with painter's tape before engraving. Catches smoke residue. Peel off after, instant clean.
• Sand lightly (220-grit) before engraving, removes surface oils.
• After engraving: brush off ash with a stiff nylon brush. Optional: light coat of mineral oil or polyurethane to lock in the contrast.
• For drama: dark walnut wash + wipe before sealing. Settles into the engraved valleys, leaves the high points light. Like Brass Black for wood.

Acrylic (CO2)

3D engraving on acrylic gives a frosted-relief effect. Best on cast (not extruded) acrylic.

Speed	400-500 mm/s
Power	22-30%
Line interval	0.06 mm
Image mode	Grayscale
Air assist	Minimum (just enough to keep smoke/dust off the lens; not enough to round engrave edges)

For "lit edge" relief signs: engrave the depth map in reverse on the back of clear cast acrylic, then mount with LED edge lighting. The engraved relief glows from within.

Leather (CO2)

Leather takes shallow relief beautifully, a few hundred microns of depth gives a tactile, embossed feel.

Substrate	Veg-tanned leather, 2.5mm+
Speed	450 mm/s
Power	15-22%
Line interval	0.08 mm
Image mode	Grayscale
Passes	1-2

Mask with paper tape before engraving. Avoid chrome-tanned leather (releases toxic chromium compounds).

Stone, slate, marble (CO2)

Slate is the easiest. White-on-black mark with surprising depth perception even from minimal actual depth (~50-100 µm).

Speed	300 mm/s
Power	25-35%
Line interval	0.08 mm
Image mode	Grayscale

Marble is fragile. Drop power 25%, use 2-3 passes instead of 1. Grayscale produces a chalky white relief on dark stone that reads as 3D from a few feet away.

Coated tumblers (CO2)

The fiber's "color anneal a tumbler" trick has a CO2 cousin: ablate the powder coat in graded depth to reveal the metal underneath at varying brightness.

• Substrate: powder-coated 30oz tumbler.
• Approach: Grayscale image, bright areas ablate fully (full metal exposure), darker areas ablate partially (stained appearance), pure black leaves coating intact.
• Settings: 400 mm/s, 30% power, line interval 0.1mm, single pass.
• Effect: "tonal" engraving instead of pure on/off, looks more like a screen print than a logo etch.

Metal (fiber): recap from Relief Coin module

For metal you want fiber laser + Lightburn galvo edition with 3D Sliced image mode (NOT Grayscale, those are different). 3D Slice does the multi-pass depth slicing automatically. See Relief Coin Engraving for the full workflow, settings, and post-processing.

STL vs depth-map AI: when to use which

Path	Best for	Skill required	Time
STL render	Custom designs, precise depth control, repeatable production	Some 3D modeling	30-90 min per design
AI depth map (SculptOK, tiling-zoedepth)	One-off custom orders, AI-generated artwork, no 3D modeling skill	None	2-5 min per design
Photo with manual depth (Photoshop)	Logos, simple insignia, when only specific layer-style depth is needed	Photoshop intermediate	15-45 min per design

Common pitfalls

• "My engrave is shallow" on wood. Single-pass grayscale rarely exceeds 1mm depth. Use the multi-pass approach for dramatic relief.
• "My engrave looks pixelated." Source image is too low resolution. Re-render at 600+ DPI or upscale carefully.
• "My engrave is inverted (subject sunken)." Toggle Negative Image on the layer. Or re-export the depth map with inverted brightness.
• "My fine details are lost." Tonal range too compressed, re-stretch in Photoshop with Levels.
• "My wood looks burnt and cracked." Speed too low or power too high. Drop power 5%, increase speed 50 mm/s, run multiple passes instead.
• "My acrylic is melting weirdly." Air assist too low, or extruded acrylic instead of cast. Switch to cast.
• "My marble cracked." Power was too high. Marble is brittle, 1-2 passes at low power. Never single-pass aggressive.

The seven-step optimization workflow

1. Source → STL (Blender / Aspire / scanned).
2. Render depth pass at final part dimensions, 600+ DPI.
3. Tonal stretch (Photoshop Levels: anchor 0 and 255).
4. Gaussian blur 1-2 px to soften steps.
5. Final crop with clean background (alpha or pure black).
6. Import to Lightburn as image. Set image mode: 3D Sliced (galvo metal) or Grayscale (gantry wood / acrylic / leather).
7. Test on scrap material first, single small test piece (50×50mm) to verify settings before committing to the full part.

Sources: Lightburn 2.0 docs (3D Sliced / Grayscale image modes), Blender depth pass tutorials, Aspire / Carveco workflow guides, community wood-engrave forums for species-specific settings.