What Is 3D Relief Carving?
When most people think of CNC routers, they picture flat-cut signs or simple 2D profiles. But with the right tools and workflow, your CNC router can become a digital chisel—capable of sculpting beautiful 3D relief carvings from wood, foam, or even plastics.
3D relief carving refers to a technique where the CNC machine creates a raised or recessed image on a flat surface. Unlike full 3D objects (like statues), reliefs are mounted on a backplate, much like the artwork carved into old cathedral walls or coin faces.
CNC relief carvings bring texture, depth, and visual interest to a project. From wildlife scenes and portraits to decorative panels and topographic maps, 3D carving CNC projects unlock artistic possibilities that 2D routing can’t match.
Best Materials for 3D Carving
Not all materials respond the same way to 3D CNC carving. Since the process involves long run times, fine detail, and variable depths, choosing the right stock can make or break your project.
Top Material Choices for Relief Carving
Hardwood (Maple, Cherry, Walnut)
- Pros: Holds crisp details, polishes beautifully, high-end appearance
- Cons: More expensive, slower to machine
- Best for: Fine art panels, portraits, heirloom pieces
Softwood (Pine, Cedar)
- Pros: Affordable, faster to cut, widely available
- Cons: Can tear out during fine passes; less durable
- Best for: Prototypes, rustic designs
MDF
- Pros: Extremely uniform, easy to carve, low cost
- Cons: Produces fine dust, requires sealing, lacks grain character
- Best for: Painted carvings, CNC tests, practice models
HDU Foam (Sign Foam)
- Pros: Very fast to cut, zero grain, ideal for large carvings
- Cons: Requires paint to look good, less durable
- Best for: Outdoor signage, large decorative panels
Software to Generate 3D Models
Creating 3D carvings requires more than just G-code generation—it starts with creating or sourcing a proper 3D model file. You don’t need to be a sculptor to start; several accessible workflows can get you carving quickly.
Common 3D File Types for Relief Carving
- STL (Stereolithography): The most common format for relief carving.
- OBJ: Popular in 3D modeling; compatible with many CAM tools.
- Heightmaps (grayscale images): Useful for terrain or topographic maps.
Recommended Software for CNC 3D Design
Carveco Maker / Maker+
Ideal for relief carving workflows. Import, edit, and generate toolpaths from STL or grayscale heightmaps, with advanced bas-relief tools.
Vectric Aspire
Popular among hobbyists. Built-in 3D modeling and relief creation tools; easily converts 2D artwork into 3D features.
Fusion 360
Not ideal for artistic reliefs, but powerful for mechanical 3D parts. Great for hybrid projects that combine art with functional components.
Blender + STL-to-CAM Software
Use Blender for modeling, then export to a CAM tool such as MeshCAM or Kiri:Moto for toolpaths. Steeper learning curve but powerful and free.
Where to Find Ready‑Made 3D Relief Models
- Design & Make: Large catalog of decorative STL files for Aspire/Carveco.
- Thingiverse / Printables: Free 3D models; many can be adapted for relief carving.
- TurboSquid / CGTrader: Stock 3D assets (some free, some paid).
Toolpath Strategies for Clean Results
Once your model is ready, generating the correct toolpaths is essential for clean, accurate 3D carving.
Roughing Pass vs. Finishing Pass
Roughing Pass: Clears bulk material quickly using a larger end mill (e.g., 1/4" flat or ball nose). Leave a small stock offset for the finishing pass.
Finishing Pass: Uses a smaller bit (e.g., 1/8" or 1/16" ball nose) to follow detailed surface contours with slower feed rates and small stepover.
Key Tips for Clean Carving
- Use ball nose bits: The round tip yields smooth curves and detailed contours.
- Dial in stepover: For detail work, target 8–12% of the bit diameter.
- Increase Z resolution: Smaller vertical stepdowns capture more vertical detail.
- Tune feeds & speeds: Match settings to bit size and material hardness.
Toolpath Cleanup
Use “rest machining” with a very fine bit to capture small features missed by the finishing tool. Consider Z‑level finishing if your model includes vertical walls or flat ledges.
Finishing and Mounting Your Art
Sanding and Cleanup
Remove fuzzies or fibers left by ball nose bits using soft detail brushes, sanding sponges, or a rotary tool for tight areas. Avoid flattening delicate features by sanding too aggressively.
Finishing Options
- Clear coat: Show off the natural grain and depth with shellac or polycrylic.
- Stain + clear: Adds contrast and mood; lightly sand between coats.
- Painted accents: Use acrylic paint to highlight key features.
- Highlight and glaze: Apply a dark glaze and wipe back to enhance depth.
Mounting and Display Ideas
- Wall mounting: Add sawtooth hangers or French cleats.
- Framing: Floating or shadowbox-style frames create a polished look.
- Backlighting: Consider LEDs behind translucent resin or thin acrylic for dramatic effects.
Final Thoughts
3D carving isn’t just about showing off—it’s about expanding what’s possible with your CNC router. Whether you’re crafting a decorative wildlife panel, a personalized portrait, or a unique business sign, relief carving projects let you create dimensional, textured art that tells a story.
While the workflow may seem intimidating at first—3D modeling, toolpath planning, and fine finishing—once you complete your first successful relief carve, you’ll be hooked. It’s a skill that blends artistic vision with technical precision and pays off in stunning results.
