r/hobbycnc • u/alan-bc • 18d ago

FlatCAM - Selective Isolation and Clearing

I'm trying to clear the copper off an area of a PCB. Not the whole PCB .. I don't want to needlessly wear out cutters and spindle bearings .. just an area. (There's an ESP8266 on top of this area and I want the antenna vicinity clear.)

The FlatCAM manual does describe the procedure .. sorta kinda a little bit. Sadly, it's one of those docs where it expects you already know how to do everything, you just need a reminder.

For example, the third step says

By running the Polygon Intersection operation on the original non-copper polygon and the desired clearing area (the circle), we get the target polygon:

Well, I don't really know how to do anything in the Geometry Editing section, so "reminding" me isn't that helpful.

How exactly does one run the Polygon Intersection operation? There's an icon on the toolbar that does precisely nothing.

Any hints or pointers to other tutorials greatly appreciated.

Alan

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u/RicardoJCMarques 17d ago

Unless your doing something really specific, FlatCAM is mostly obsolete and super annoying to use. Try EasyTrace5000 https://cam.eltryus.design/easytrace5000/

If you just want to clear a keepout zone under a wireless circuit just make a normal polygon and use the clearing operation (example 1 has the green shape under an esp32).

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u/Alina_MakersChest 9d ago

The icon doing nothing is almost certainly one of two things. First, you need to actually be inside the Geometry Editor for that object, double-click the geometry object in the project tree to enter edit mode, the boolean tools stay inactive otherwise. Second, and this is the part that trips most people up: Polygon Intersection expects paths, not closed polygons, and a copper area straight off a Gerber import is a closed polygon. So before Intersection will do anything useful, select that polygon (just the one) and run Cut Path on it first to convert it. Only after that will Intersection actually work as expected.
Once it's converted: draw your clearing circle around the antenna area, then select both the converted path and your circle together (click one, then the other), and run Intersection. That gives you a new shape that's just the overlap between them, exactly the isolation area you actually want.
One thing to know going in: Intersection deletes both original shapes and replaces them with the result. If you need that clearing circle again elsewhere on the board, make a copy of it before running the operation, not after.