kicad-developers team mailing list archive

[Lorenzo Marcantonio <l.marcantonio@xxxxxxxxxxxx>]

On Wed, Dec 04, 2013 at 12:28:55PM -0800, Cirilo Bernardo wrote:
> That's a good idea. If we could extrude a courtyard rather than the silkscreen outline then we would meet all the functional mechanical requirements of IDF3 by simply adding a height to each component. Extruding an outline of the silkscreen won't quite work though since in many cases it won't serve the purpose of the mechanical fit check. On the other hand, maintaining component outline files in the manner that we maintain VRML files would be a royal pain in the ass - so much so that, in the absence of courtyard outlines, I am tempted to simply extrude the silkscreen outlines simply to provide some sort of markers and give the users a general idea of the component locations. I see the IDF exchange with MCAD as good enough for many purposes, but things will be much better when/if I get around to doing proper 3D modeling.

How other people do it (e.g. Altium, IIRC), extended by my own ideas:
provide layers for explicit mechanical extrusion, when it's missing extrude
the assembly layer, when everything else fails do the courtyard. And the
specified model obviously wins if it's specified. The extrusion layer
would be used for non rectangular things (like aluminum caps or simple
polygonal items like THT power resistors), assembly for most rectangular
things, and obviously a model for critical stuff like connectors,
switches and buttons.

Rationale: the courtyard contains the pads and the fabrication excess so
it's way too big. The assembly box (usually folder-thing shaped) is in
maximum material condition so it would be a really good candidate (*if*
it's only an outline... for example I put an arrow there to indicate
the insertion side for connectors; that would break it).
However it's always a box so an intermediate shape would be useful
(instead of a full model): that would be the mechanical extrusion layer
(maybe height could be encoded there as width, like in eagle? it's ugly,
I know). The silk screen is absolutely not-useful since it's usually not
even a closed shape (example: the inspection bar/dots). In fact some
silk conventions *break open* the shape to indicate pin 1!

To make things simpler: just use the specific layer and put a function
in the module editor to copy the assembly or whatever and create
a default extrusion (with specified height); the user would then edit it
if needed. Then during exports just process that layer and ignore the
other stuff.

> Ultimately the MCAD doesn't care about the holes; with SolidWorks I simply have a cut outline named "PTH" which contains the location and size of all PTH and the same goes for NPTH. Even the mounting holes which happen to be plated go into PTH, so I can't even distinguish mounting holes from others based on the name or grouping within SolidWorks.

It seems that's a 'nobody care' value, then:D (still hoping for a flag
to denote important holes, for filtering plots too!).

-- 
Lorenzo Marcantonio
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