FlatCAM pratical tutorial: copper traces geometry – Part 2

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Now we have a base project to start work. First step is to create a series of geometries that become the passes used by CNC to isolate the copper traces.

For all the milling working I use this type of bits

Pyramid Engraving Bits 20 Degree
Pyramid Engraving Bits 20 Degree

You find here

I prefer the 30° version because It’s more durable, and works like a charm.

PCB drill bits
PCB drill bits

You find here

Now I must say that most of the operation are the result of experience, so you must know that this operations aren’t the better operations, but they are my better solution for milling PCB.

Generate trace isolation geometry

Now we are going to select with double click the Gerber PCB_PCF8574_03_copperBottom.gbl where we can find the information about the traces.

FlatCAM isolation of copper bottom panel with arrow
FlatCAM isolation of copper bottom panel with arrow

Now you have the Isolation routing panel, here you have 3 parameter:

  • Tool dia (black): the diameter of the tool you are going to use
  • # Passes (blue): the number of isolation passes you want (more passes more isolation of the trace)
  • Pass overlap (red): the percentage of Tool dia to overlap between the pass

Now here I’d like to do a consideration, my idea is that we prefer more possible copper area, because if there are some problem or autolevel is not properly setted we don’t put out the work.

So I’d like to extend tool dia as much as possible, and you check this parameter directly on the draw of the Geometry generated, search for the closest items anche check if the geometry is broken.

Here an example with a tool size of 0.57

FlatCAM Beta Tool dia broken geometry
FlatCAM Beta Tool dia broken geometry

So I’m going to reduce the tool dia since 0.55 and the size permit to the geometry to have the correct size

FlatCAM Beta Tool dia for a perfect geometry
FlatCAM Beta Tool dia for a perfect geometry

This is a perfect solution for me, the result is a clean board with a good quantity of copper, and you have better result if you want more thin copper trace, but if you need more space from trace to trace (like for smd) you must try more fitted Tool dia.

As you can see I do 3 passes, you can understund the mean of # Passes in the draw, this value is combined with Pass overlap that set how much overlap, for example with 50% overlap you have:

image/svg+xml 50% Copper 1° pass 2° pass 3° pass

Or if you insert a 33% overlap

image/svg+xml 33% Copper 1° pass 2° pass 3° pass

The idea is to remove more copper as possible, so bigger Pass overlap is better, but you must pay attention, first we are using a bigger Tool dia, and 50% probably cover only 20% of material.

If you use a too big overlap the result is this

FlatCAM wrong pass overlap
FlatCAM wrong pass overlap

Here a correct pass overlap

FlatCAM perfect pass overlap
FlatCAM perfect pass overlap

As you can see there is a check Combine this is quite usefully, if you check It instead to create one file for pass

  • PCB_PCF8574_03_copperBottom.gbl_iso1
  • PCB_PCF8574_03_copperBottom.gbl_iso2
  • PCB_PCF8574_03_copperBottom.gbl_iso3

It generate only one file with all 3 geometry

  • PCB_PCF8574_03_copperBottom.gbl_iso

I prefer to create 3 or 4 file and group only first 2.

To group 2 or more geometry you must select they with Shift + mouse click or Ctrl + mouse click than go to Edit --> Conversion --> Join Geo/Gerber/Exc --> Geo, as result you obtain a new file with the join of the geometry you select.

FlatCAM Beta join geometry
FlatCAM Beta join geometry

I group only 2 geometry because I create a first gcode for this, I send the work to my CNC than If the isolation seems sufficient I don’t do more, if It isn’t sufficient I generate an additional gcode only for the third isolation geometry and so on with normally the limit of 5.

Here an example of single pass

Ciclop board for Arduino nano

beautiful, but very difficult to solder and quite dangerous, humidity or dust can create a short circuit.

ABB Aurora PCB multiple step

Result of first 2 passes

Don’t worry, the PCB isn’t clean, at the end when you clean It you got a good surprise.

FlatCAM PCB pcf8574 first 2 passes
FlatCAM PCB pcf8574 first 2 passes

The same but clean with sandpaper

FlatCAM PCB pcb8574 first 2 passes milled clean
FlatCAM PCB pcb8574 first 2 passes milled clean

Result last pass

FlatCAM PCB pcf8574 last pass
FlatCAM PCB pcf8574 last pass

Thanks

  1. FlatCAM pratical tutorial: introduction, installation and import
  2. FlatCAM pratical tutorial: copper traces geometry
  3. FlatCAM pratical tutorial: clean non copper area
  4. FlatCAM pratical tutorial: silkscreen geometry
  5. FlatCAM pratical tutorial: countour
  6. FlatCAM pratical tutorial: gcode and milling a PCB

You can find Gerber, fritzing, images and FlatCAM project files here.


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