Outlines data

EAGLE can produce outlines data which can be used for milling prototype boards.

The User Language Program outlines.ulp implements the entire process necessary to do this. The following is a detailed description of what exactly has to be done to produce outlines data with EAGLE.

Preparing the board

Outlines data is produced by defining a POLYGON in the layer for which the outlines shall be calculated. This polygon must have the following properties:

If a polygon with these properties is present in your board, the RATSNEST command will calculate it in such a way that its contours correspond to the lines that have to be drawn by the milling tool to isolate the various signals from each other. The fillings of the calculated polygon define what has to be milled out if you want to completely remove all superfluous copper areas.

Extracting the data

The outlines data can be extracted from the board through a User Language Program. The outlines.ulp program that comes with EAGLE implements this entire process. If you want to write your own ULP you can use outlines.ulp as a starting point. See the help page for UL_POLYGON for details about how to retrieve the outlines data from a polygon object.

Milling tool diameter

The diameter of the milling tool (and thus the Width of the polygon) must be small enough to fit between any two different signals in order to be able to isolate them from each other.
Make sure you run a Design Rule Check (DRC) with all Clearance values for different signals set to at least the diameter of your milling tool!

Non-zero values for the Isolate parameter can be used when working sequentially with different milling tool diameters in order to avoid areas that have already been milled.

Cleaning up

Make sure that you always delete the _OUTLINES_ polygon after generating the outlines data. Leaving this polygon in your drawing will cause short circuits since this special polygon does not adhere to the Design Rules!

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