At 06:43 AM 2/7/2002 +1100, Ian Wilson wrote:
But then why stop there - the design rules should allow us to check that 
the component fitting under the one with some "off-pcb" space is not too 
high.  I may be able to fit an 0805 under a ROM socket possibly even an S0 
in some parts but not a fat tant.  Or what about fitting small components 
under the curve of a large axial cap?  The height available varies with 
distance from the centre line of the component.

Yes. I made no suggestion that Protel should stop at any particular place....

I do think that my suggestion about allowing internal pockets may be 
overkill for a first implementation. That, being relatively rare, should be 
covered by design rule exceptions.

>I seem to remember that one of the PCB packages has a design rule system 
>that can deal with addition and subtraction etc.  Using this (and with 
>some extra design rule functions like DistanceToComponentBorder, and/or 
>Overlap etc that give us measures off the component(s) being DRC'ed) we 
>could get more elaborate.  Cost would be a significant slow down in DRC 
>and great scope for complex design rules not doing what we actually wanted.

Collision detection should be pretty fast, and then, once there are no 
collisions, checking for enclosure should also be pretty fast. I don't 
think that the slowdown would be significant, there are plenty of other 
things much more complex which are DRC'd. Remember, most components would 
have a rectangular outline, so not too many primitives would be in the outline.

Outline at MMC (maximum material condition, the largest that the part could 
be, or, in this case, additional allowance might be made for manufacturing 
requirements) is a very simple concept, I'm surprised that it was not 
implemented long ago.

Abdulrahman Lomax
Easthampton, Massachusetts USA

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