Contouring and Isolation Routing

Contouring creates CNC toolpaths around copper tracks, pads, vias and copper areas. Follow these steps to calculate and verify the isolation paths before manufacturing.

1. Check the imported PCB

Before calculating contours:

Confirm that the PCB dimensions and visible geometry match the source design.
Check the top and bottom copper layers separately.
Confirm that pads, tracks, vias and copper zones appear correctly.
Make sure a suitable contouring tool is available in the Tool Library.

Check the Zones setting: copper zones hidden with the Zones control are excluded from contour calculation and generated G-code.

Tool Library : to calculate contours, you must have a suitable tool ( V-BIT ) in the Tool Library. If not available, please first create a contouring tool in : Parameters > Tool Library and add a suitable tool for contouring.

2. Open the Contouring window

Select Calc. Contours on the main toolbar, or open Manufacturing > Calc. Contours.
Select the contouring tool that will be installed in the CNC machine.
Check the displayed tip size, angle and cutting information.

TraceFab Calculate Contours window with tool, pass, layer, cut-side and offset settings — Use the Calculate Contours window to configure the isolation toolpaths.

Tool geometry matters: TraceFab uses the effective cutting width to position the tool centre and space additional passes. The physical cutter must match the selected Tool Library entry.

3. Configure the contour passes

Master Pass

Every calculation contains one mandatory Master Pass around the copper geometry. Its value is fixed at 1.

Extra Passes

Extra Passes add paths beside the Master Pass and widen the cleared isolation channel. Use only as many as the PCB requires because every additional pass removes more copper and increases machining time.

Pass Overlap

Pass Overlap reduces the spacing between adjacent passes. More overlap can prevent thin copper ridges, but also increases repeated cutting and machining time.

4. Choose the layers and toolpath position

Apply Contouring To

All Layers: calculates both top and bottom contour operations.
Top Layer: calculates or replaces only the top-side result.
Bottom Layer: calculates or replaces only the bottom-side result.

Display is separate from calculation: Show Top Layer and Show Bottom Layer only change the preview. The selected option under Apply Contouring To determines which toolpaths are calculated.

Cut Side

Outside: the normal choice for isolation routing and the default setting.
Center: places the tool centre on the copper outline.
Inside: places the tool centre inside the copper feature.

Extra Offset

With Cut Side set to Outside, a positive Extra Offset moves the contour farther away from the imported copper outline. Apply this conservatively and check all narrow clearances.

Protect the copper geometry: Center and Inside can narrow tracks, pads and copper areas. Extra Offset also changes the manufactured geometry and can reduce clearance to neighbouring features. Always inspect the complete calculated result.

5. Calculate and review the result

Select Calculate.
Wait for TraceFab to update the PCB preview.
Compare the calculated isolation paths with the imported copper geometry.

Imported PCB copper geometry before isolation contours are calculated — Before calculation: imported PCB copper geometry.

PCB preview with calculated CNC isolation contours around copper features — After calculation: isolation contours around the copper.

Review checklist

Every copper feature that requires isolation has a contour.
Tracks, pads, vias and copper areas have not been narrowed or removed unintentionally.
Extra passes create a continuous cleared channel without thin copper ridges.
The expected top and/or bottom layers contain calculated contours.
Offsets and special Cut Side settings do not conflict with narrow gaps or fine-pitch pads.

If the result is incorrect, adjust the tool, passes, overlap, layer selection, Cut Side or Extra Offset, and select Calculate again.

Contouring is now prepared. The calculated top and/or bottom contour operations are stored in the current job and become available in the Manufacturing window. Calculate does not generate G-code.