Why your laser-cut DXF was rejected: open paths and duplicate lines

Three defects account for most automatic rejections, and all three are invisible when you look at the drawing. Here is what each one actually is, why your eyes cannot catch it, and how to fix it.

Last updated 11 August 2026

When an automated cutting service rejects your file, the message is usually short and the cause is usually one of three things: a contour that is not closed, geometry drawn twice, or extra content that is not part of the cut. These are not aesthetic complaints. Each one breaks a specific step in how the machine turns your drawing into a toolpath.

Why the software cares so much

A cutting service does not cut your lines. It builds a region from them — a closed loop with an inside and an outside — and then offsets that loop by half the kerf to decide where the beam actually travels. Everything downstream depends on that: which side is scrap, which loops are interior holes, how much material to quote.

A loop that does not close has no inside. Xometry states the requirement in those exact terms: “The file should not contain open curves. Close all open curves so that the 2D sketch can be extruded.” The extrusion is the giveaway — their pipeline is trying to make a solid out of your outline, and an open outline is not a shape at all.

Duplicated geometry breaks a different step. If two identical lines sit on the same coordinates, the machine has no way to know whether you meant one cut or two. SendCutSend rejects it outright:

“Duplicate paths in your 2D vector file (.dxf, .dwg, .eps, or .ai format) will be rejected by our automated system since the laser cannot recognize or cut them.”SendCutSend, common file problems (retrieved 11 August 2026)

1. Open contours

An open contour is a cut path whose start and end points do not meet. The gap is often far below what you can see — a thousandth of a millimetre is common when geometry has been copied, mirrored, trimmed, or round-tripped through another format.

Why you cannot see it. At a zoom level where the whole part fits on your screen, a 0.001 mm gap is a small fraction of one pixel. There is no zoom level at which you would think to look, because nothing tells you where to look.

How to find it without a checker

• Try to fill it. Nearly every CAD tool can hatch, shade, or fill a closed region and will silently refuse on an open one. In Fusion, a closed sketch profile shades; an open one does not. In AutoCAD, BOUNDARY or HATCH fails to find a boundary. This one test catches most cases in seconds.
• Select the outline and check what you get. If clicking the outline selects one closed polyline, it is closed. If it selects a single edge, your outline is loose segments and every corner is a potential gap.

How to fix it

• AutoCAD and clones: JOIN or PEDIT → Join to merge segments into one polyline, then confirm the polyline reports as closed. Set a join tolerance only as large as the real gaps.
• Illustrator: select the two open endpoints and Object → Path → Join.
• Inkscape: node-edit the path, select the two end nodes, and use Join selected nodes.
• Parametric CAD (Fusion, Onshape, SolidWorks): fix it in the sketch and re-export. Do not patch the DXF — the next export will reintroduce it.

2. Duplicate and overlapping paths

Duplicates come from ordinary work: copy-paste, mirroring a half and leaving both halves along the centreline, exploding a block, importing the same layer twice. Two lines on identical coordinates draw exactly one line on your screen.

There are three distinct cases, and they are not equally serious.

• Exact duplicates. The same segment twice. Always a defect.
• Partial overlaps. Two segments sharing part of their length — typically a line drawn slightly long over another. Almost always accidental, and the messiest to spot by hand.
• Full shared edges between adjacent parts. Two parts deliberately sharing one cut line, called common-line cutting. This one depends on your shop.

That last case is why a good checker reports rather than decides. Common-line cutting is a deliberate technique that saves time and material — and SendCutSend explicitly states it is “unable to accept designs with common-line cutting”. The same geometry is a clever optimisation at one shop and an instant rejection at another. No file-level tool can know which shop you are sending to, so anything that silently failed or silently passed a shared edge would be wrong half the time.

How to find and fix it

• AutoCAD and clones: OVERKILL deletes duplicate and overlapping geometry and reports how many objects it removed. That count is the useful part — if it removes 40 objects, you had 40 problems you could not see.
• Count entities before and after. Any dedupe operation that changes the object count found something real.
• Mirrored designs: check the mirror line specifically. A doubled centreline is the single most common source.
• Illustrator and Inkscape: there is no reliable single command. Isolate each closed shape and rebuild the outline rather than hunting stacked strokes.

3. Extra geometry that is not the part

A title block, a dimension, a note, a border, a construction line, a logo on a hidden layer — the cutter’s importer does not know which of these you meant to cut. Xometry is blunt about the consequence: “Extra-drawn features can be confused with cut geometry and cause the file processing to fail”, and it also states that files “cannot contain inserts or multiple assembled components.”

Hidden layers deserve special attention. Hidden is a display setting, not a deletion. The geometry is still in the file, and whether it gets cut depends entirely on the receiving software. Delete it rather than hiding it.

The practical order to work in

1. Delete everything that is not cut geometry, including on hidden layers.
2. Run your CAD tool’s duplicate-removal command and note how many objects it removed.
3. Join the outline into closed polylines and confirm each one reports as closed.
4. Fill or hatch each region as a final closure test.
5. Re-export, then check the exported file — not the drawing you were working in.

Step five is the one people skip. The export is where geometry gets flattened, tessellated, and re-encoded, so it is the export that can be broken while your sketch is perfect.