Two endpoints can appear to touch and still remain an open vector. Before cutting, inspect nodes, gaps, overlaps, joins, duplicate paths, and operation assignments at the final physical scale, then preview the corrected output and run a low-consequence contour test.
Do not close every gap automatically. Some paths are intentionally open for scoring, engraving, hatch marks, or construction details. Identify the intended operation before repairing geometry.
Recognize What an Open Path Changes
A closed contour has a continuous boundary. An open path has a break between its start and end nodes, even if the gap is too small to see at normal zoom.
Open geometry can affect:
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Whether a shape qualifies for a fill operation.
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Whether a cut creates a complete boundary.
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Whether a small part remains attached.
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Whether a hole or counter behaves as intended.
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Whether the preview shows the expected traversal.
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Whether a repair tool joins unrelated objects.
Separate the intended operations first:
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Cutting contours generally need the closed boundaries required by the software and process.
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Scoring and engraving may intentionally use open lines.
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Construction lines, registration marks, and centerlines may not need closure.
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Shared edges may belong to separate operations but should not automatically be welded.
A filled preview can hide a break because the software may display a region that appears closed even when the underlying paths are not. A thin outline view can also hide stacked geometry. Use node inspection and the software’s open-shape tools rather than relying on appearance alone.
Use Node and Shape Diagnostics
Open the file in node or outline view at the final physical scale. Look for:
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Two endpoints that are close but not joined.
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A visible gap between endpoints.
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Overlapping segments.
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Self-intersections.
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Duplicate paths.
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A contour that closes visually but has separate nodes.
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A clipping mask or hidden object that changes the boundary.
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A shape assigned to the wrong operation.
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A converted text or imported curve with broken subpaths.
Select the suspected object and inspect its start and end nodes. Moving a copy of the object slightly can reveal whether another identical path remains underneath, but perform that test on a duplicate working file.
LightBurn documents that Fill Mode requires closed loops, and its design-preparation tools include node editing, Delete Duplicates, Close Path, Close Selected Paths With Tolerance, and Auto-Join. Its preview is intended to show the simulated movement and laser operations before output. LightBurn design-preparation guide
Do not treat a lower open-path count as proof that the file is correct. A repair can close the wrong objects, add an unintended bridge, or alter a contour.
Set a Join Tolerance From Physical Scale
Trace the defect to its source when possible. Tiny gaps often enter during:
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Trimming or boolean operations.
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Imported DXF or SVG conversion.
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Outlined text.
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Clipping-mask edits.
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Manual node movement.
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Simplification or optimization.
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Copying geometry between applications.
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Scaling and rounding coordinates.
Repair the editable master, then regenerate the production file. A correction made only in the laser sender may disappear when the artwork is exported again.
Set the join tolerance from the actual gap and nearby intentional features. The tolerance must be large enough to close the documented defect but smaller than the nearest separation that must remain open.
LightBurn’s Close Selected Paths With Tolerance tool lets the user choose a distance threshold and either move endpoints together or join them with a new line. It also reports how many open shapes it found and closed. LightBurn Close Selected Paths With Tolerance
Do not choose a large tolerance simply because it closes more paths. A broad threshold can connect separate contours, collapse a slot, bridge a narrow opening, or change a corner.
Preserve Separate Operations
Before using Auto-Join or a tolerance-based close command, isolate the paths that are intended to form one contour. Keep cutting, scoring, engraving, and construction geometry separate.
After repair, compare the region with the approved artwork:
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Did the contour shape remain unchanged?
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Did a narrow slot remain open?
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Did a letter counter remain intact?
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Did the repair create a straight bridge across a curve?
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Did a separate score line become part of the cut?
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Did the layer or operation assignment change?
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Did the bounding dimensions remain correct?
LightBurn states that Auto-Join connects line or curve segments whose endpoints are directly on top of, or very near, each other; its documented threshold for that tool is specific to the software and version. Do not transfer that behavior or value to another program. LightBurn design-preparation guide
A hidden clipping object or unit-conversion problem can mimic open geometry. Verify the imported physical dimensions using a known reference before deciding that a gap is purely a node problem. If the file came from SVG, use the same size-preflight method described in Why SVG artwork imports at the wrong size in laser software if that URL is live and verified.
Preview Fill and Cut Behavior
Preview the corrected file before sending it to the machine. Check:
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Cut order and layer order.
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Contour closure.
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Double passes.
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Corner shape.
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Small holes and counters.
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Bridges and retained tabs.
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Whether freed parts remain supported.
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Whether filled regions overlap only as intended.
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Whether the output matches the design.
A preview can show that the software recognizes a closed contour, but it cannot prove that the physical edge will fully separate. Kerf, material variation, workholding, focus, and process conditions affect the final cut.
Run a low-consequence contour coupon on suitable identified material. Compare the corrected file with the original for closure, corner behavior, double lines, small features, and whether the intended part releases. Do not use universal power, speed, pass, or material assumptions; follow the exact machine and material documentation.
If a part fails to release, do not immediately enlarge every gap or increase exposure. Confirm whether the failure is geometry, kerf, focus, material, motion, or process-related.
Add Path Integrity to File Release
Make path integrity part of the production preflight. Archive:
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Editable source artwork.
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Corrected revision.
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Repair method and tolerance.
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Open-path result.
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Duplicate-path check.
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Final preview.
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Physical test result.
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Approved sample or reference.
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Software and export versions.
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Operation and layer assignments.
Repeat the preflight after:
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Customer artwork changes.
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Scaling.
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Node simplification.
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Text conversion.
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SVG or DXF export.
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Boolean operations.
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Clipping edits.
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Import into another application.
A released file should not depend on an operator noticing a tiny gap at the machine. The intended object, operation, physical dimensions, and repair history should already be clear.
A TwoTrees machine may be relevant to the final workflow, but its product page does not prove that a particular file, material, geometry, or cut result will work in every configuration. The TwoTrees TS2 laser engraver is an option to inspect only after the file and process requirements are understood. Verify the exact model, controller, software, material, and safety documentation before purchase or production.
Auto-close can connect the wrong objects
Two endpoints that are close on screen may belong to separate letters, slots, score lines, or neighboring contours. A lower open-path count can therefore represent a worse design.
Before auto-closing, ask:
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Are these endpoints supposed to belong to the same object?
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Is the gap smaller than the nearest intentional separation?
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Will the repair change a hole, slot, counter, or bridge?
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Does the resulting contour match the approved artwork?
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Does the operation remain assigned correctly?
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Does the final-size preview still show the intended result?
Use the smallest documented tolerance that repairs the known gap, then inspect every changed region. If the source contains fully separate paths, a tool designed to close one path’s start and end nodes may not be the correct repair method. LightBurn notes that its tolerance-based close function works on individual paths whose start and end nodes are disconnected; it does not connect arbitrary separate paths into one contour. LightBurn Close Selected Paths With Tolerance
Stop and consult the exact software documentation when the file contains clipping masks, compound paths, imported geometry, unusual text, or operation-specific overlaps that the repair tools may reinterpret. The reliable goal is not zero open paths at any cost; it is correct geometry at the intended physical scale.
