gEDA-dev: PCB - XY values of centrioid in BOM/DXF exproter(was gEDA-user: PCB Element for a Molex 71661-2068?)

[Timmerman, Bert]

Hi Peter,

> What do other packages with 3D modelling use for their models?

I don't know, ... yet.

> Do you really mean centre of gravity, or some kind of geometric
centre?
> (Thinking of modelling components with non-uniform material density).

Well, erm, you're right, center of gravity isn't exactly the right
description.

> I'd have expected to use some centroid in the plane of the PCB, and to
> have the Z axis of the attach point on the component correspond to the
> plane of the PCB it rests on.
>
> Eg. SMDs would start at Z=0 and go upwards in Z the height of the
> component.
>
> A through-hole capacitor would have its base at just above Z=0
> (clearance for lead expansion / contraction), have the cylinder
> extending up with +ve Z, and leads protruding down with -ve Z.
(assuming
> we go so far as modelling leads).

I used the conventions you described as a matter of fact.

And I did model the leads in the parts I have sofar.

For most parts I have a model with leads with the full length as
specified in the datasheet, and a model with cut-off leads for through
hole parts protruding through the pcb for about 1.0 mm.

Sofar I have some 500+ models in AutoCAD (and SAT file format) which I
use for mechanical designs.

Kind regards,

Bert Timmerman.