Re: [Pcb2gcode-devel] best way to add text to pcb

[John S. <jrs...@op...>]

Thanks for your reply Patrick, and sorry for the delay. Took me  awhile 
to make thing mostly work.  Here is what I have managed so far.

I have now successfully made a DS board with some legible text on it. 
Stuffing the board and making the hardware and firmware work distracted me.

I ended up adding the text to the outline layer. As well as the 
rectangular mill outline.
Exported the outline as gerber from pcb.
I wrote a short perl script to read in the outline gerber, and split it 
to a standard outline (just the rectangle) and also turn the text gerber 
direct to gcode.

That gcode was then processed to height probe the board ( with 
Etch_Z_adjust.2.2.py) and then cut text after the main board top 'etch'.

I have 2 issues to fix with this flow before I would recommend anyone 
else consider it.
firstly - I should have used an otherwise unused layer, not outline. 
Should be an easy tweak.

Secondly, height probing.   I'm finding that essential to achieve decent 
void width control.
see 
http://www.cnczone.com/forums/pcb_milling/82628-cheap_simple_height-probing.html

However you can only do this once on a side before etching the board, 
since you lose the continuous copper electrical connection.

This seems to imply that I shoul merge the text gcode fragment into the 
main milling gcode.  I haven't automated that yet.

But I'm pretty convinced that the text should be milled as a positive 
layer, straight down the gerber, and the tracks as a negative layer, ie 
mill around the gerber.

I'm not sure whether  I prefer voroni milling or perimeter milling.

I do want to minimize mill time so cutting the isolations exactly once 
seems pretty important.

john



  On 16/01/12 02:45, Patrick Birnzain wrote:
>
> Hi John,
>
> I don't know any reasonable way of adding text to the board - maybe it
> works if you set the offset to the radius of your engraving bit, but
> that is applied to the whole board.
>
> I've not used it myself, so I'm not 100% sure what it really does, but I
> think the --milldrill option might be useful for you. Seems it does
> everything with the bit that's used for cutting out the board, though -
> if you have smaller bore holes, it still just uses the big one.
> You could try to split your excellon drill file in two - one with the
> big bores, and one with the smaller ones; then run pcb2gcode with
> big_diameters.cnc and --milldrill, save drill.ngc, and run pcb2gcode
> another time with the small diameters.
>
> Let me know if that works the way you want, it should be easy to add
> another option to pcb2gcode to do that automatically.
>