DXF, SVG and STEP contour checker

A laser, waterjet or plasma cutter follows the contours of a drawing, and its software needs every contour closed. An outline that misses its own start by a hundredth of a millimeter has no inside, a line drawn twice is cut twice, and a stray fragment costs a pierce of its own. A mesher for a simulation needs the same and more: faces that close exactly, edges shared exactly between neighboring faces, and no tiny edges or nearly collinear pieces, which force needlessly small elements. Drawings exported from other programs, traced from images or put together from several sources break these rules in ways that do not show on screen. The checker marks each problem where it is and repairs the drawing, for a cutter or for a mesher.

The checks

The legend of the drawing lists every kind of problem with the number left in the repaired drawing, so the numbers drop as the repair settings rise; the status line also gives how many the drawing had as drawn. A click on a legend entry shows or hides its marks, and the edge ends and the drawing as it was are entries there too. Mark small features sets when two ends count as a gap, an edge as tiny and a face as small; switched off, none of the three is marked.

• An open end is an end of an edge that no other end meets.
• A gap is two ends closer than the gap distance that do not meet. Farther apart, they are two open ends.
• A crossing is two edges that meet where not both of them end, such as a center line across an outline or a line ending on another one, or a point where three or more edges end.
• A doubled line is two edges that share a stretch, which a laser would cut twice.
• A tiny edge is shorter than the tiny limit.
• A small face has less area than the face limit.

The repair

Layer by layer, ends closer than the gap closing distance are joined, edges are cut where they cross, and a doubled stretch is kept once. planex2d's Simplify then removes edges below the limit, merges lines that are nearly collinear, removes free edges, which touch no other edge at either end, and fits arcs to chains of short edges where that is switched on. Every fit is checked against the edges it replaces and rejected if it strays further than its tolerance. The closed contours of each layer become faces with the contours inside them as holes, and the faces of all layers are glued into one shape, in which small faces are removed or merged into the neighbor they share the longest boundary with.

Cut length and pierces

The cut length is the length of every edge after the repair, and every contour, closed or open, needs one pierce. The table gives both per layer, since a layer of center lines or engraving is usually not cut through.

For meshing

A mesher needs closed faces that share their edges exactly, and tiny edges, nearly collinear pieces and tessellated curves make a mesh needlessly fine. The STEP and BREP files hold the repaired faces glued into one shape. See Defeaturing and simplification in the docs for the steps in Python.

Reading as drawn

A DXF file is read entity by entity, as it was drawn, so that nothing is joined or cut before the check. SVG, STEP and BREP files are read by planex2d's readers, which already join the ends that meet and cut crossing edges where they cross. In these files the check finds open ends, gaps and tiny edges, but no crossings or doubled lines.

Units

The checker works in the unit the file names, and the sliders, the hover texts and the result show it. A DXF file names its unit in its header, an SVG file in its width and height, and a STEP file in the file itself. A file that names none, such as every BREP file, is taken in meters, the SI unit, and so are the sliders before a file is open. The settings are kept in SI units, so they keep their size when a file in another unit is opened. The repaired drawing is saved in the file's unit, or in millimeters where a format cannot name it.

1. Load

   The page loads Python and planex2d into this tab. Your browser keeps both in its cache, so later visits start faster.

2. Read

   The browser reads the file from your disk into memory. No request carries it to a server.

3. Check

   planex2d's Diagnose finds the open ends, gaps, crossings and doubled lines, and the checker adds the tiny edges and small faces.

4. Repair

   A copy of the drawing is repaired with the settings on the left and checked again, at every change of a setting.

Supported files

Run it in Python

The checks and the repair are planex2d's own calls. Install it and see Defeaturing and simplification and Geometry checks in the docs. The example finds the gap of the traced plate sample, closes it and measures the repaired plate.

$ pip install planex2d

import planex as px

wires = px.FromDXF("traced-plate.dxf", scale=1, layers=["0"])
found = px.QuickSketch(wires, copy=True).Diagnose(gap=0.05)
print({kind: len(faults) for kind, faults in found.items()})
fixed = [w.Simplified(close_gaps_smaller=0.05, remove_edges_smaller=0.001) for w in px.Wires(wires, 0.05)]
plate = px.Face([w for w in fixed if w.IsClosed()])
print("area", plate.mass)

Privacy

Limits

• This tool reads and writes planar STEP and BREP files only.
• Text, dimensions, hatches and images are not read; the checker looks at the geometry only.
• Pierces count the contours; lead-ins and the order of the cuts are not planned.
• In the browser, planex2d runs in one thread, so large drawings take longer than in Python on your machine.
• A file that fails? Open an issue on GitHub and attach the file if you can.