kicad-developers team mailing list archive

[Cirilo Bernardo <cirilo_bernardo@xxxxxxxxx>]

----- Original Message -----

> From: Lorenzo Marcantonio <l.marcantonio@xxxxxxxxxxxx>
> To: Kicad Developers <kicad-developers@xxxxxxxxxxxxxxxxxxx>
> Cc: 
> Sent: Thursday, December 5, 2013 10:10 AM
> Subject: Re: [Kicad-developers] Development of IDFv3 export
> 
> 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.
> 


Thanks for your comments. The more I think about it, the more I suspect that the least intrusive compliant IDF solution is to maintain IDF footprint files in a manner similar to what we do with VRML.  I'm not really keen on that though since I see IDF as being of rather limited use. I'll post on the user's list and see if I can get some comments from habitual IDF users.  For my own use I like the ability to generate my board solid model with holes in it and I'm quite happy to spend a few minutes manually putting in models of the more critical components; even in a previous project with over 400 components on the board there were fewer than 20 components which required good models.

>>  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!).
> 


Well, it's an enforced "nobody cares" value since even an expensive MCAD package will not give you what you want even when IDF provides it. I wonder if CATIA does any better.  What kind of flags would you put on holes and how would you use those flags? I'm just curious - not volunteering to code such a thing of course. :P

- Cirilo