How to Create a DXF File in Inkscape for CNC Cutting

CNC routers cannot read images such as JPG, PNG, or PDF files that contain pixels. They only understand vector paths. Each vector line becomes a toolpath. The CNC machine follows the centre of that path using a rotating cutting tool. If your file contains:

• Images instead of vectors
• Open or broken lines
• Overlapping shapes
• Incorrect scale

Inkscape is a free vector drawing program used to create 2D designs for CNC cutting. If you do not already have it installed:

1. Go to www.inkscape.org
2. Click Download
3. Choose the correct version for your system (Windows, Mac or Linux)
4. Follow the installation steps

This is the most common cause of incorrect CNC cuts. If your units are wrong, your parts will be the wrong size.

Follow these steps:

• File → Document Properties
• Set Display Units to mm
• Set Custom Size Units to mm
• Check Scale = 1.0
• Set precision (2–3 decimal places)

Why this matters?

Although Inkscape allows you to draw anywhere on the canvas, setting the page size helps you design more accurately.

How to set page size:

• Go to File → Document Properties
• Under Custom Size, enter your sheet width and height in mm

Why set the page size?

• It helps you visualise your sheet size.
• It prevents you from designing parts larger than your material.
• It makes layout and spacing easier to plan.

• 2440 × 1220mm (8×4 sheet)
• 3050 × 1220mm (larger sheets)

Important:

CNC machines only cut along vector lines, not images or visual effects. Make sure your design follows these rules:

• Use shapes or the Bezier tool to create lines and curves
• Avoid bitmap images (JPG, PNG) — machines cannot cut them
• Keep everything 2D (very important) — no 3D effects, gradients, shadows, or fills
• Draw clean paths — the machine will follow the centre of each vector line

Before exporting your DXF, every object in your design must be converted to paths. CNC machines cannot cut text or shapes unless they are paths.

1. Ungroup any grouped objects:
   • Select the object → Object → Ungroup
2. Convert to paths:
   • Select your object → Path → Object to Path

Why this matters:

• Text must be converted so it doesn’t rely on fonts.
• Shapes must be converted so the CNC machine sees the outlines.
• Prevents missing letters or substituted fonts when your file is opened on another computer.

Workflow summary:

CNC machines only follow the centre of vector lines. Fills and stroke thickness do not affect cutting.

• Remove all fills from your objects — only the outline matters
• Set stroke width to a thin line (hairline, 0.01–0.1mm)

Why this matters:

• Fills are ignored by CNC machines
• Thick strokes do not increase the cut width. The tool follows the centreline only

Pro tip:

For CNC cutting, every path must form a complete loop. Open paths can cause incomplete or broken cuts.

1. Use the Node Tool to inspect your shapes
2. Look for gaps or loose ends in the paths
3. If a path is open, select the end nodes → Join Selected Nodes

Why this matters:

Duplicate or overlapping lines are a common cause of problems in CNC cutting.

Why it matters:

• CNC machines will cut overlapping lines twice
• Waste cutting time

How to fix:

• Select all objects → Path → Combine to merge overlapping lines
• Or inspect manually in Wireframe view to see hidden duplicates

CNC cutting tools are round, which means they cannot cut perfectly sharp internal corners.

Key concepts:

• Internal corner radius: The smallest radius the tool can cut inside a corner
• Dog bones or T-bones: Extra material cut away at inside corners to allow square tabs to fit

Why this matters:

Tip:

CNC machines have physical limitations. Very small details or thin sections may not cut properly or can break during machining.

Things to watch for:

• Tiny details may be too fragile to cut
• Thin bridges between shapes can snap
• Internal cut-outs need enough space for the tool to fit

General guidance:

• Minimum slot width = your tool diameter
• Avoid extremely tight internal radii that the tool cannot reach

Before exporting your DXF, make sure every measurement is correct.

• Use Inkscape’s Measuring Tool to check all dimensions
• Confirm width and height of each part
• Check hole positions and spacing between features
• Double-check gaps and clearances for joinery

Reminder:

Once your design is ready, you need to save it in the correct DXF format for CNC machines.

1. Go to File → Save As
2. Choose Desktop Cutting Plotter (AutoCAD DXF R2013)

Recommended settings:

• Use LWPOLYLINE (lightweight polylines for cleaner paths)
• Base unit = mm
• Disable splines if the option appears

Why DXF R2013:

• Newer DXF versions (2018, 2020, etc.) can introduce features that CNC software often doesn’t support, such as advanced splines, text formatting or 3D data.
• These extra features can cause missing lines, incorrect scaling or errors when the file is imported.
• DXF R2013 keeps the file simple, compatible and reliable, while preserving all 2D vector paths your CNC machine needs.

Validating your DXF file is crucial before sending it for CNC cutting.

1. Close the file after saving
2. Re-open the DXF in Inkscape or another program
3. Check the scale. Ensure all parts are the correct size
4. Inspect for missing elements — make sure nothing disappeared during export
5. Check line joins — all paths should still be closed and properly connected

Optional:

• Open the DXF in a free DXF viewer to double-check everything before submission

Before sending your DXF to a CNC service, make sure your file passes this checklist:

• ✅ Units set to millimetres (mm)
• ✅ Design drawn at full size (1:1 scale)
• ✅ All objects converted to paths (including text and shapes)
• ✅ No fills — outlines only
• ✅ All paths fully closed
• ✅ No duplicate or overlapping lines
• ✅ Inside corners checked (dog bones or reliefs added if needed)
• ✅ Dimensions and hole positions verified
• ✅ Material thickness specified
• ✅ Tool size and cutting limits considered

For those looking to take their designs to the next level, you can prepare CNC-ready joinery directly in Inkscape. This section covers common features used by cabinet makers and shopfitters.

Key joinery elements to include:

• Hinge hole layout – Accurately position holes for hinges so doors align perfectly
• Multiple drillings – Use different layers or colors for holes of different diameters or depths
• Grooves and pockets – Add comments in your DXF specifying cut depth (e.g., 5 mm or 10 mm)
• Shelf pin spacing – Mark consistent holes for adjustable shelves
• Dados and rebates – Cut grooves and recesses for shelves, panels and drawer bottoms
• Back panel recess – Ensure the back panel slot is correctly sized and aligned

Pro tip:

Even experienced designers sometimes make avoidable errors when preparing DXF files for CNC. Avoid these pitfalls to save time, material and frustration:

• Sending PDFs or images instead of DXF – CNC machines cannot read pixel-based files.
• Forgetting the outer profile – Parts won’t cut correctly without a defined edge.
• Designing in inches by mistake – CNC machines expect millimetres; scaling errors can ruin parts.
• Using stroke width to represent depth – Depth must be communicated via annotations, layers, or colours.
• Forgetting to label parts – Helps assembly, especially for multiple panels or complex projects.
• Not accounting for kerf – Tool width removes material; slots and joints may end up too tight.
• Tight tolerance joinery without clearance – Slots, tabs, and internal corners need a small gap for proper fit.