Guide · Laser cutting
How to prepare DXF files for optimal laser cutting nesting
Whether you're using an online nesting tool for laser engraving or a browser-based nesting engine like NextMax, the DXF you feed in decides how tightly your parts pack and how cleanly they cut. Here's the prep checklist we run every job through.
1. Lock down units
DXF has no reliable unit header. Half the files that fail online nesting silently re-import at 25.4× the intended size because the exporter wrote inches while the nester assumed millimetres. Before export, set your CAD document units and confirm the bounding box in the nesting tool matches the physical part.
2. Close every contour
True-shape nesters treat open polylines as line art, not part outlines — they can't pack them. Join endpoints, close arcs into polylines, and delete stray construction lines. In most CAD tools a single "join" or "pedit" pass fixes 90% of imports.
3. Separate cut, engrave, and reference on layers
Laser workflows almost always split power/speed by layer. Export cut contours, engrave paths, and reference geometry on distinct DXF layers so the nester can nest on the outer boundary while your laser controller still sees the engrave passes. When possible, name layers by operation (CUT, ENGRAVE, REF) — that's a cleaner handoff than colour-only conventions.
4. Bake in kerf and part spacing
A tight nest that ignores kerf produces parts that measure light. Decide up front whether the nester adds spacing (NextMax accepts a part spacing value in mm) or whether you'll offset each contour outward by half your kerf in CAD. Pick one — never both, or you'll waste material.
5. Place lead-ins on flat edges, not corners
For laser and plasma cutting, a lead-in that enters at a sharp corner leaves a visible pip on the finished edge. Add lead-ins in CAD along a flat run — 3–5 mm is usually plenty — and keep them on the waste side. Cloud nesters won't move them for you, so ship them in the DXF you upload.
6. Purge blocks, hatches, and text
Nesting engines have to rasterise or triangulate every entity. Filled hatches, block references, and TrueType text explode the geometry count and slow the optimiser without adding value. Explode blocks, convert text to outlines (only if you actually want to cut it), and delete hatches before export.
7. Test with one sheet before batching
Once your DXF is clean, nest a single sheet, download the SVG preview, and check orientation, spacing, and layer mapping against your laser's post-processor. Ten minutes of validation on sheet one saves scrapping sheet ten.
Try it on your next job
NextMax's online nesting tool for laser engraving runs true-shape packing with a genetic optimiser in the browser — no installer, no plugin. Drop in a prepped DXF and you'll see the packing efficiency in seconds.