dxf-fix

dxf-fix is a Python command-line tool to clean and reconstruct DXF files for photolithography and other precision manufacturing workflows. It flattens arcs and splines into straight segments, snaps nearly-coincident endpoints with micrometer precision, removes duplicate segments, and reconstructs closed, independent shapes using clean LWPOLYLINEs.

Many CAD tools export DXF files with curves and loosely connected endpoints, which:

• Prevent proper nesting or shape detection in lithography tools like KLayout, and even more importantly the control softwares that power laser cutters, photoplotters, mask service providers and maskl-less lithography equipment
• Cause rendering artifacts or missing features
• Require manual editing to unify and simplify structures

dxf-fix automates the cleanup process and ensures your layout geometry is robust and ready for downstream applications.

Features

• Flattens LINE, ARC, CIRCLE, POLYLINE, and LWPOLYLINE entities into line segments
• Snaps endpoints using KD-tree clustering with tunable micrometer precision
• Deduplicates symmetric segments (e.g., (A, B) == (B, A))
• Reconstructs independent closed paths from raw segments
• Outputs clean LWPOLYLINEs suitable for fabrication and visualization
• Provides a high-resolution debug overlay image to inspect snapping behavior
• Falls back to saving open paths as LINEs when closure is not possible
• Optionally scales and flips the output geometry

Installation

Install Python 3.9+ and required packages using pip:

pip install ezdxf matplotlib scipy

Optional: Create an Isolated Environment with Mamba / Micromamba

If you'd prefer to isolate the dependencies using mamba or micromamba, you can create and activate an environment like this:

mamba create -n dxf-fix python=3.10 ezdxf matplotlib scipy
mamba activate dxf-fix

Then, run the script as usual:

python fix_dxf.py input.dxf output.dxf

Usage

Run the tool from the command line:

python fix_dxf.py input.dxf output.dxf

• input.dxf: input DXF file (e.g., exported from Onshape)
• output.dxf: cleaned DXF file with reconstructed shapes

You can configure snapping precision and additional output transformation parameters at the top of the script:

DEFAULT_UNIT = "mm"
DEFAULT_PRECISION_UM = 0.1
DEFAULT_ARC_SEGMENTS = 100
OUTPUT_SCALE = 1.0  # Set to e.g. 0.5 to reduce the size by half
FLIP_Y = False      # Set to True to vertically flip the output

These transformation options are useful when:

• Your DXF export is scaled differently (e.g., 2:1 or 10:1)
• You need to mirror the layout vertically for lithography or alignment purposes

Output

• A cleaned DXF file with closed LWPOLYLINEs. Any open paths that could not be closed will be written as LINEs.
• A summary of fixes and issues in the command line
• A diagnostic image reconstruction_overlay.png showing snapping and open paths, see example below:

Verification and Editing

We recommend to view the output DXF file visually in the open source KLayout software, also on GitHub. The viewer hatches closed areas nicely which indicates that lines are indeed closed and ready for the lithography machine or mask service.

You can double check that the final scale in micrometer of features in your file is correct by using the "Ruler" tool to measure an edge of known size.

Switch the software opening mode to "edit mode" in order to delete lables you might not need.

License and Attribution

This project is licensed under the BSD 3-Clause License. See the LICENSE file for details.

It has been developed by Tobias Wenzel – Wenzel Lab. If you use this tool in academic work, please consider citing relevant lab publications or linking back to this repository.