Non Copper Clearing

Non-Copper Clearing (NCC) creates a Geometry object with toolpaths that remove the copper between the features of a Gerber or Geometry object. It clears the board around the traces, so the unwanted copper is removed. Use it to clear the copper of a PCB that does not need copper outside the traces.

Where to find it

• Plugins menu: select NCC (shortcut Alt+N).
• Plugin Toolbar: click NCC.
• The plugin panel opens in a new tab of the side panel. The tab shows the plugin name. Select an object in the Project tab, or choose it in the Source Object combo box.

Screenshot placeholder: images/Non-Copper-Clearing-1.png - the whole NCC panel, with the Tools Table, the parameters of one tool and the Common Parameters visible.

Quick start

1. Select the copper object in the Source Object combo box. Set Type to Gerber or Geometry.
2. Enter a cut width in Tool Dia, then click Search and Add.
3. Select the tool row. Keep Operation on Clear and Method on Seed.
4. Set Overlap for this tool. Check that Connect and Contour are on.
5. Click Preview. The area to clear appears on the canvas.
6. Click Generate Geometry. A new Geometry object appears in the Project tab.
7. Mill the result with Milling.

Screenshot placeholder: images/Non-Copper-Clearing-2.png - the preview of the area to clear on the canvas, with the Preview button in the panel.

Parameters

Source Object

Parameter	Description	Default
Type (radio)	The type of the source: Geometry or Gerber. It sets the kind of objects in the Source Object combo box.	—
Source Object (combo box)	The object to clear.	-
All selected objects	When checked, every Gerber or Geometry object selected in the Project tab is cleared with the same tools and parameters. Each result is a new object. Area Selection works with one object only.	Off (tools_ncc_multi_objects)

Tools Table

The table holds the tools that the algorithm uses. The columns are described in Tool table columns.

Parameter	Description	Default
Tools Table	The tool pool. Only the tools in this table are used.	-
Tool order (combo box)	The order in which the tools are used. Default: the order of the table. Forward: from the smallest to the biggest diameter. Reverse: from the biggest to the smallest diameter.	Reverse
Tool Dia	The diameter of a new tool. Used by Search and Add, Optimal and Pick from DB.	0.1
Optimal	Finds a tool diameter that gives a complete isolation.	-
Search and Add	Adds a tool with the diameter of Tool Dia. A background search in the Tools Database looks for a matching tool. If nothing is found, a default tool is added.	-
Pick from DB	Opens the Tools Database and adds the tool you select.	-
Delete (trash icon)	Deletes the selected tools in the table. Select a row first.	-

Parameters for the selected tool

These controls hold the values of the selected tool. Each tool keeps its own set of values.

Parameter	Description	Default
Operation (radio)	Clear: the regular copper clearing. Isolation: the clearing must always be complete. If the isolation fails, the copper clearing fails too.	Clear
Milling Type (radio)	Climb: best for precision milling and to reduce tool usage. Conventional: useful when there is no backlash compensation. Enabled only for Operation Isolation.	Climb
Overlap	How much (percentage) of the tool width each pass overlaps the previous pass. Lower values are faster. Higher values give more paths and a slower job. Raise it if areas are not cleared.	40 %
Method (combo box)	The algorithm for the copper clearing. See the choices below.	Standard (tools_ncc_method)
Margin	The bounding box margin.	1.0
Connect	When checked, the lines between the resulting segments are drawn to reduce tool lifts.	On
Contour	When checked, the tool cuts around the perimeter of the polygon to trim rough edges.	On
Direction (radio)	The cut direction of the clearing passes: None, Climb or Conv. Climb is the wall on the right of the tool, with an M3 spindle. See Direction. Disabled for Operation Isolation.	None (tools_ncc_clear_milling)
Final cleanup	After clearing, the next smallest selected tool with this option on clears the reachable residual copper. It may cross cleared areas. It keeps the copper clearance and the clearing boundary. See Final cleanup.	Off
Offset	When checked, an offset is added to the copper features. The clearing finishes at this distance from the copper.	Off
Offset value (field)	The offset distance, in mm, or inch in an inch project. Shown and used only when Offset is checked.	0.0
Apply parameters to all tools (button)	Copies the values in the form to all the tools in the table.	-

Method choices:

• Standard: a fixed step inwards from the outline of the polygon.
• Seed: an outward clearing from a seed point.
• Lines: parallel lines.
• Combo: tries Lines first. If it fails, it tries Seed, then Standard.
• Crosshatch: two families of parallel lines, at 90 degrees from each other. The Angle field sets the direction of the first family. It is shown only for this method.

Operation notes: with Isolation, the Overlap, Method, Margin, Connect, Contour, Direction, Final cleanup and Offset controls are disabled. Only Milling Type is active.

Common Parameters

These values apply to all the tools.

Parameter	Description	Default
Rest Machining	When checked, the copper is processed from the biggest selected tool. What the tool cannot clear goes to the next smaller tool. The Tool order is then set to Reverse and cannot be changed. The rest machining has its own margin, connect, contour and offset controls.	Off
Rest Margin, Offset	The same meaning as above. They replace the normal controls while Rest Machining is on.	-
Rest Connect, Contour	They apply to all the rows. When you click one, its value is written into every row of the Tools Table. The rest machining then uses the Connect and Contour of each tool row, not one panel value.	-
Selection (combo box)	The area to clear. Itself: the area is the object itself. Area Selection: draw the area on the canvas with left clicks. Reference Object: the area of another object. Polygon Selection: pick the copper-free regions with the mouse.	Itself
Type (combo box, for Reference Object)	The type of the reference: Gerber, Excellon or Geometry.	Gerber
Reference object combo box	The object whose area is cleared. Shown for Reference Object.	-
Shape (for Area Selection)	Square: a rectangle. Polygon: a polygon drawn with clicks.	Square
Check validity	When checked, the tool diameters are checked against the smallest gap of the object. The check shows if the tools provide a complete isolation.	On

Exclusion areas

The exclusion zones belong to the source object (the Gerber or Geometry object in the Object box), not to the plugin:

• The zones are saved with the project. Copy and Join keep them. Panelize does not copy them.
• The zones move with the object: move, scale, mirror, rotate, skew, a units change and the undo of a transform.
• With All selected objects, Add area and Delete all act on every selected object, and the job uses the zones of all of them.
• Each add and each delete is 1 undo step.
• The zones of the source are on the canvas only while the panel shows that object. Reset keeps the zones. Closing the panel or opening another plugin takes them off the canvas.
• The Geometry object that the job makes keeps a copy of the zones that the job used and always shows them. When you delete that object, its zones are deleted too. A later change of the source zones does not change it.

Parameter	Description	Default
Use exclusion areas	When checked, the exclusion zones of the source object are removed from the area to clear, for Generate and Preview. The tool keeps its radius away from the zones.	—
Shape (radio)	The shape used to draw an exclusion zone: Square or Polygon.	—
Zones	The number of exclusion zones of the selected object. A read-only count.	0
Add area	Draws exclusion zones on the canvas and adds them to the selected object. Left click to draw. Right click or Escape to finish.	-
Delete all	Removes all the exclusion zones of the selected object.	-

Buttons

Parameter	Description	Default
Preview	Draws the area that would be cleared on the canvas. Nothing is created. For Area Selection, the zones of the last Generate are used.	-
Generate Geometry	Creates the Geometry object with the clearing toolpaths.	-
Reset Tool	Resets the parameters of the selected tool.	-

Advanced

Tool table columns

The Tools Table works the same way in Isolation Routing, Paint and this plugin. This plugin has four columns:

Column	Meaning
#	The tool number. With the order Reverse, the algorithm starts with the biggest diameter. Only the tools that create clearing geometry stay in the result.
Diameter	The cut width in the material, in mm, or inch in an inch project.
Shape	The shape of the tool, as a combo box in each row: C1, C2, C3, C4, B, V or L.

Shape codes:

• C1 to C4: a circular tool with 1 to 4 flutes.
• B: a ball tip milling tool.
• V: a V-shape milling tool.
• L: a laser.

The V-tip values of a V tool (tip diameter and tip angle) come from Preferences > Plugins, in the NCC group. This form does not show them. For a V tool, the effective diameter is:

diameter = V-Tip Dia + 2 x |Cut Z| x tan(V-Tip Angle / 2)

Direction

Direction sets the cut direction of the clearing passes. None keeps the direction of the algorithm. Climb cuts with the wall on the right of the tool, for a spindle that turns clockwise (M3). Conv (conventional) is the opposite: the wall is on the left. Note these points:

• Lines and Crosshatch scan lines are not oriented. Only their contour and gap rings follow the direction. The Laser_lines method is not oriented.
• With a direction, the G-code keeps the path direction. A multi-depth open path is not reversed between the depths. The tool retracts at the end of the path, goes back to the start, and plunges again.
• A closed ring keeps its direction at every depth.
• Rings around the outer boundary of the area turn counter-clockwise for Climb. Rings around islands and holes turn clockwise. Conv is the opposite.
• The Tcl option is -clear_milling.

Screenshot placeholder: images/Non-Copper-Clearing-3.png - the Direction radio in the parameters of the selected tool, with Climb selected.

Polygon Selection

Set Selection to Polygon Selection. Then click Generate Geometry, and click in the canvas:

1. Left click on a copper-free region to pick it. Left click again on the same region to remove it.
2. Right click or press Enter to start the clearing.
3. Press Escape to cancel.

The Margin, Offset and exclusion areas apply as for the other modes. The Tcl option is -single x,y.

Screenshot placeholder: images/Non-Copper-Clearing-4.png - copper-free regions picked on the canvas in Polygon Selection.

Rest Machining and the tool order

With Rest Machining, each tool processes only what the bigger tool did not reach. The order is forced to Reverse. When you clear Rest Machining, the order goes back to the value it had before.

Each tool uses its own Connect and Contour from its row in the Tools Table. The rest Connect and Contour boxes in the Common Parameters write their value into all the rows when you click them.

Final cleanup

Final cleanup removes copper that the normal passes did not reach. It does not change the copper clearance. It follows the same rules as the final cleanup of Paint:

• It uses the next smallest tool that has a diameter above zero and a free area left after the copper is removed. It does not stop at the smallest tool if that tool has no free area.
• The cutter stays inside the free area. The plugin makes the area smaller by the cutter radius once.
• The border is cut first when Connect of the tool is off.
• The message "Final cleanup finished. Some residual copper could not be cleared with this tool." shows only for real stock. A corner residue of a round tool gives no message. Stock that holds a disc of 10 % of the tool diameter is real stock.

The incomplete warning

After the last tool, the plugin checks the copper that is left. If the left area holds a disc of 10 % of the diameter of the last tool, the plugin shows "Some areas were not cleared with these tools." The result is still created. Use a smaller tool, Rest Machining or Final cleanup. After a final cleanup, only the message of the final cleanup shows.

Beginner Mode

Beginner Mode hides these controls: the Add from DB section, Operation, Milling Type, Offset, Rest Machining, and Apply parameters to all tools. When you switch to Beginner Mode, the plugin also writes new values to every tool in the table:

• Operation is set to Clear.
• Milling Type is set to Climb.
• Offset is set to off, with the value 0.0.
• Rest Machining is set to off.

Switch back to Advanced Mode before you change these values again. The level button is at the top of the panel, and the permanent setting is in Preferences.

Tcl

The Tcl command is ncc (also ncc_clear). It runs the same clearing as the plugin, but it uses only its own arguments and the NCC preferences. It does not read the panel or the Tools Table. It uses the exclusion zones stored on the object. The polygons of -exclude are added to them for that run only, and the object does not change. The options -single x,y, -clear_milling none|climb|conv and -exclude are available. See Tcl Command Reference.

Limits

• Area Selection works with one object only.
• The Method Combo tries three methods in turn. The result is the first one that gives paths.

See also

• Isolation Routing - cuts the isolation around the traces.
• Paint - paints the copper pattern.
• Follow - cuts along the centre line of the traces.
• Cutout - cuts out the PCB outline.
• Optimal - finds the tool diameter for a complete isolation.
• Tools Database - the tools for Search and Add and Pick from DB.
• Geometry Object - the output object.
• Milling - turns the Geometry into G-Code.
• Preprocessors - the G-Code formats for the machine.
• Keyboard Shortcuts