Gerber2CNC - KiCad to G-code Converter

Overview

Converts single-sided KiCad PCB Gerber files to CNC milling G-code for trace isolation and hole drilling. Includes interactive visualization to verify toolpaths before milling.

Requirements:

• Python 3.6+
• shapely library: pip install shapely
• KiCad project with generated Gerber and drill files

Usage

python gerber2nc.py <project_path> [output_name]

Example:

# For project at /home/user/myboard/
python gerber2nc.py /home/user/myboard

# Custom output filename
python gerber2nc.py /home/user/myboard myboard_mill

Input Files (KiCad naming convention):

• <project>-F_Cu.gbr - Front copper layer (traces + pads)
• <project>-Edge_cuts.gbr - PCB outline
• <project>-PTH.drl - Through-hole drill file

Output:

• <project>.nc or <output_name>.nc - G-code file
• Interactive visualization window

Workflow

1. Generate Gerbers in KiCad:

   • Plot → Layers: F.Cu, Edge.cuts
   • Drill files → Excellon format

2. Run the script:

   python gerber2nc.py /path/to/your/project

3. Review Visualization:

   • Green/Black background: PCB outline
   • Red lines: Original traces (varying thickness)
   • Blue circles/rectangles: Pads
   • White lines: Calculated milling toolpaths
   • Black circles: Drill holes
   • Close window when satisfied

4. Load G-code into your CNC:

   • T1: 0.2mm engraving bit (trace milling)
   • T2: Small drill (~0.8mm)
   • T3: Large drill (>0.85mm)

Limitations

• Single-sided PCBs only (front copper layer)
• No rotated pads or complex apertures
• KiCad-specific file formats and naming
• Outline must be one continuous polyline in Edge.cuts
• No copper pours or ground planes

Parameters (edit in code)

Search for "parameters" to modify:

• offset_distance = 0.22 - Initial tool offset from traces
• num_passes = 3 - Number of milling passes
• path_spacing = 0.2 - Spacing between passes
• cut_depth = -0.1 - Trace milling depth
• spindle_speed = 12000 - RPM
• feed_rate = 450 - mm/min

Troubleshooting

• "No edge cuts defined": Draw PCB outline in KiCad Edge.cuts layer
• Empty visualization: Check Gerber file paths and KiCad plot settings
• Milling paths look wrong: Adjust offset parameters or verify trace widths
• Drill holes missing: Ensure PTH drill file is generated

Note: The script marks (but doesn't cut) the PCB outline. Use a bandsaw for final separation.