I’ve seen the same workflow failure hundreds of times in support tickets: someone exports a DXF from Fusion 360, uploads it to nesting software, and either the parts show up at the wrong size, half the geometry is missing, or the nest runs but the export doesn’t open correctly in LightBurn.

Almost every failure traces back to one of three things: a DXF with open contours, units set wrong at export, or extraneous geometry that confuses the parser. This tutorial covers the full workflow from CAD to cut-ready file, including how to avoid those failures before they happen.

What you need before you start

A DXF file containing the part(s) you want to cut. If you have multiple part types, you can upload them individually or combined in one DXF.
Your sheet dimensions (width × height) in millimetres
Your kerf width (measure this on your machine — see our kerf compensation guide)
The quantity of each part you need

If you’re working from SolidWorks, Fusion 360, FreeCAD, or AutoCAD, export your part outlines as DXF. For sheet metal, export flat patterns, not folded 3D bodies.

Step 1: Prepare your DXF file

Nesting software reads the outline geometry of each part. Before uploading, ensure your DXF is clean:

What works well

Closed polylines (LWPOLYLINE) — the most reliable geometry type for nesting. Ensures the part outline is a single connected loop.
Circles and arcs — handled correctly by all major nesting tools
Splines — supported, but complex splines may be approximated into polyline segments

Common DXF issues that cause problems

Open contours — if the part outline isn’t fully closed, the nesting software may fail to recognise the part boundary, skip the part, or produce incorrect placement. In your CAD tool, run a “close contour” or “join curves” operation before exporting.

Multiple overlapping lines — DXF files sometimes contain duplicate geometry (two identical lines on top of each other). This confuses nesting algorithms. In AutoCAD or FreeCAD, use OVERKILL (AutoCAD) or a cleanup command to remove duplicates.

Extraneous geometry — dimension lines, title blocks, centre marks, and text should be on separate layers from your part outlines. Either delete them before export or ensure you export only the part outline layer.

Incorrect units — DXF files don’t always embed unit information reliably. A part exported in inches will appear 25.4× smaller than intended when read as millimetres. Lapas shows a part preview after upload; check that the displayed dimensions match expectations. If they don’t, re-export with explicit millimetre units or use the scale override in the upload step.

Recommended export settings (Fusion 360)

File → Export → DXF
Select the sketch or flat pattern you want to export
Ensure “Export as” is set to DXF
Units: millimetres
Geometry: curves (not approximated as lines unless necessary)

Recommended export settings (SolidWorks)

File → Save As → DXF/DWG
Options → Select “Flat pattern” for sheet metal
Under “Export”, select only the “Flat pattern” layer
Units: millimetres

Step 2: Upload your parts

In Lapas, start a new job and drag your DXF file(s) onto the upload area. Lapas will:

Parse the DXF and detect individual closed contours
Show you a thumbnail preview of each detected part
Let you set the quantity of each part

For a DXF with multiple different parts (a common pattern when exporting all parts from an assembly), each closed contour is detected as a separate part. You’ll see them listed individually in the parts panel.

Tip: If a part has internal holes (e.g., a bracket with mounting holes), Lapas handles hole-in-part geometry correctly: the holes are treated as cutouts, not separate parts.

Setting quantities

Set the quantity for each part. The nesting optimizer will try to fit exactly that many of each part onto the minimum number of sheets.

For a mixed job (say, 20 of part A, 15 of part B, and 8 of part C), set each quantity individually. The optimizer will mix all part types across sheets to achieve the best overall utilization.

Step 3: Configure sheet parameters

The sheet configuration panel sets the constraints the optimizer works within:

Sheet dimensions

Enter your stock sheet size in millimetres. Common stock sizes:

Steel plate: 2500 × 1250 mm, 3000 × 1500 mm, 6000 × 2000 mm
Plywood/MDF: 2440 × 1220 mm (8×4 ft)
Acrylic: 2050 × 3050 mm (common cast sheet)
Aluminium: 2500 × 1250 mm

If you have remnant sheets of non-standard size, you can enter exact dimensions. Lapas will prioritize fitting parts on those first.

Kerf width

Set your measured kerf width. See the kerf guide for how to measure this accurately.

Minimum part spacing

Any additional gap beyond kerf. Useful for:

Plasma cutting: 1–3 mm extra clearance for heat-affected zone
CNC routing: bit entry/exit clearance
Laser: usually 0 (kerf alone is sufficient)

Rotation rules

Free rotation — parts can be placed at any angle. Produces the best utilization for most irregular shapes.
Fixed angles (0°, 90°, 180°, 270°) — useful when grain direction, surface finish, or bend lines require parts to run in a specific orientation
No rotation — all parts stay in their uploaded orientation. Lowest utilization; use only when required.

For most laser and plasma jobs, free rotation gives significantly better utilization.

Number of sheets

Lapas automatically determines the minimum number of sheets needed. You can also set a maximum sheet count if you’re limited to a specific stock quantity.

Step 4: Choose a nesting engine

Lapas offers two engines:

Fast engine (Heuristic)

Results in 5–30 seconds for most jobs
Good utilization, typically 80–90%
Best for quick quotes, first-pass layouts, or time-sensitive jobs

Deep optimizer (Metaheuristic / Sparrow engine)

Runs for 30 seconds to several minutes depending on job complexity
Higher utilization, typically 85–95%
Best for production runs where material cost savings justify the extra wait

For a production job on expensive material (steel, aluminium, carbon fibre), always run the deep optimizer. The extra 2–5% utilization improvement pays for itself in material savings.

Step 5: Run the nest and review results

Click Nest (or Start). Lapas shows the nesting happening in real time, with parts appearing on the sheet as the algorithm places them.

Reading the results

After the run completes:

Per-sheet stats:

Sheet dimensions and material
Parts placed on this sheet
Utilization % for this sheet
Estimated material area wasted

Job-level stats:

Total sheets used
Total parts placed / total requested
Overall utilization %

What if utilization is low?

If the result looks worse than expected:

Try free rotation — if you had rotation locked, enabling free rotation usually improves utilization by 10–20%
Run the deep optimizer — if you used the fast engine, try the metaheuristic for a more thorough search
Mix part quantities — sometimes adding one more of a small part fills an awkward gap on the sheet
Check part geometry — if parts are being placed with large gaps around them, the DXF outlines may be larger than expected (check for extraneous geometry)

Step 6: Export for your CNC

Once you’re satisfied with the layout, export it for your machine.

DXF export

The default export. Produces a DXF file with the nested layout, all parts placed at their correct positions and rotations on the sheet coordinate system.

The Lapas DXF export is structured:

Each part on its own layer
Clean closed polylines (no duplicates, no orphan geometry)
Compatible with LightBurn, RDWorks, LaserCut Pro, SheetCam, Fusion 360 CAM, Mastercam, and all standard CAM software

Open the exported DXF in your CAM software and apply toolpaths, lead-ins, and kerf compensation as usual.

PDF report export (Pro plan)

The PDF report includes:

Visual layout for each sheet
Sheet count, utilization %, and wasted area per sheet
Part list with quantities and placement summary
Useful for quoting jobs, work orders, and customer-facing documentation

G-code and PLT export

For workflows where you want Lapas to produce cut-ready output without a separate CAM step, G-code and PLT exports are available. These include basic toolpaths suitable for most 2-axis CNC cutting workflows.

Common questions

Can I nest parts from multiple DXF files in one job?

Yes. Upload each DXF file separately and Lapas will add all detected parts to the parts list for the same job. Set quantities for each part type and run the nest across all of them together.

What if my DXF has parts from different thicknesses?

Nesting treats all parts as flat 2D outlines and doesn’t track material thickness. If you’re mixing thicknesses (which would typically mean separate cutting setups), run them as separate jobs with separate sheet configurations.

The part preview shows the wrong size — what happened?

Usually a units mismatch. Lapas reads the DXF unit header, but not all CAD tools write it reliably. Check the preview dimensions. If they’re 25.4× too small, your DXF was exported in inches but read as mm. Re-export with explicit mm units, or use Lapas’s scale override field on the upload step.

Can I save a job and come back to it?

Yes, with a Pro plan. Job history saves your part uploads, settings, and results for later retrieval or re-nesting.

My parts have tabs or bridges — will Lapas handle those?

Lapas nests the part geometry as uploaded. If your DXF already has tabs designed in, they’re part of the outline and will be included. If you want Lapas to add tabs automatically, that feature is on the roadmap. Email [email protected] to add your vote.

How to Nest DXF Files for CNC Cutting — Step-by-Step Tutorial