Re: Guide pins on smd solder mask.. #pcbgcode


John Johnson
 

If I follow your question: pcb-gcode doesn't do any tool offset for tool diameter (other than when creating track isolation/etch files). If there is a line to be cut in the milling layer, the center of the tool will follow that line. One workaround is to create lines on the milling layer that are offset when you lay them down. The easiest way is to set the line width to the tool diameter, and use that as a guide.
It might be possible to create custom components based on the ones you have, with any cutouts offset to compensate for tool diameter.


Regards,
John

On 31 Jul 2020, at 5:46, peterg1000 via groups.io wrote:

In order to properly locate a stencil over an etched circuit board I have placed circular smd pads at appropriate places on the board.  Holes to accommodate guide pins are placed centrally on this pad.  When the matching stencil is generated it is  square and slightly larger than the original smd pad.  Two questions arise, firstly - is it possible to generate circular holes in a stencil, and secondly - is the oversize intended?

After a lot of checking it would seem that in the case of my circular pad, the final hole ends up half a tool diameter larger than the original pad size.  Viewing the cutouts for other devices on the board, they would appear to be similarly oversized as well.

For example I placed an smd pad 0.05" diameter on the circuit board and the coordinates on the stencil for the sides of the matching square hole Gcode turn out to be 0.04413 in length.  With a tool diameter of 0.01182" (3mm ) I would have expected this to be 0.050" -  0.01182" (i.e.0.03818" ).  Curiously enough this is almost exactly half a tool diameter smaller than the actual value. Is this intended, an error in calculation or just co-incidence ?

Peter Harrison

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