Getting from a blank canvas to a clean, cut-ready SVG is straightforward once you understand a handful of rules. Most CNC failures aren't machine problems — they're file problems. This guide covers the fundamentals and shows you how to avoid the errors that waste material.
What makes an SVG “CNC-ready”?
A CNC router or laser cutter follows paths — it doesn't fill regions with colour or read gradients. A CNC-ready SVG has these properties:
- Closed paths for any shape that should be cut all the way through. Open paths are fine for engraving.
- No overlapping strokes. Where two paths cross, the router will cut the overlap twice, burning or tearing the material.
- Minimum feature size ≥ 3 mm for most router bits. Thinner features snap off or burn through.
- Black strokes on white background. Most CAM software treats dark paths as cut lines and ignores fills.
- Real-world units. Design in mm, not pixels. 1 px ≠ 1 mm.
The 5 most common mistakes
1. Open paths on through-cut shapes
If a path isn't closed — even by a fraction of a mm — the router will lift and move instead of completing the cut. Always close paths for anything you want fully cut out. In ShapeShift, the CNC Validator panel flags every open path with a one-click fix.
2. Designing in pixels
A 100 px circle exported from Illustrator without unit conversion lands at 35 mm on your machine — not 100 mm. Always set your document units to millimetres before you start and double-check the exported G-code preview before cutting.
3. Too many nodes
Overly complex paths — common when tracing photos — create thousands of tiny line segments. This bloats G-code, slows the controller, and creates visible stepping on curves. Use Path > Simplify to reduce node count while keeping the shape smooth.
4. Forgetting kerf
Your router bit removes material — typically 1–6 mm — as it cuts. For parts that need to fit together (box joints, slots), you must offset the toolpath inward by half the bit diameter. ShapeShift's G-code export has a kerf offset field that handles this automatically.
5. No tabs on through-cuts
Without holding tabs, a fully cut-out piece can shift just before the last pass finishes, ruining both the part and potentially the bit. Add 2–4 small tabs that keep the piece attached to the stock, then break them off with a chisel after cutting.
Layer strategy
Organise your design into layers by operation type, not visual grouping:
- Through cut — shapes cut all the way through (full depth, tabs recommended)
- Pocket — recessed areas not cut all the way through
- Engrave — surface marks, text, fine detail
- Score — very shallow lines for fold guides or decoration
- Drill — holes at specific coordinates
Each layer gets its own feed rate, cut depth, and pass strategy in the G-code exporter. ShapeShift builds this directly into the layer system so you can set cut type per layer before you ever open the export dialog.
How AI speeds up the workflow
The traditional workflow — draw in Illustrator, export SVG, open in CAM, fix errors, export G-code — takes 20–40 minutes even for experienced designers. ShapeShift compresses this to under 2 minutes:
- Describe your design in plain language (“60 mm hex coaster with 3 mm rounded corners and a bolt hole at each vertex”)
- ShapeShift generates the SVG, pre-assigned to the correct cut layers
- Validate — the CNC Validator catches any issues automatically
- Export — G-code ready for your machine, with kerf, tabs, and machine profile applied
Try it now
Open ShapeShift and describe your first design. The AI handles the SVG geometry — you focus on what to make.
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