_________
Brian G.
A software arc test:
Make 6 1 mil thick circles in PCB,
1 -> 1 inch diameter,
2 -> 1.003 inch,
3 -> 0.100 mil,
4 -> 0.103 mil
5 -> 0.010 mil,
6 -> 0.013 mil.
Generate a software arc based gerber, then on a new PCB, import.
Zoom in and compare. Also, assign separate nets, using select by
connected copper, and play with the clearance rule.
Also, is it possible that the aperature matching tolerance setting may
affect the definition of the software arcs. I think if I remember
correctly, in the older Protel PCB, there was even another
rounding/definition settings to the gerber generator.
________
Brian G.
----- Original Message -----
From: "Abd ul-Rahman Lomax" <[EMAIL PROTECTED]>
To: "Protel EDA Discussion List" <[email protected]>
Sent: Wednesday, September 28, 2005 11:28 AM
Subject: RE: [PEDA] arcs in Gerber go the wrong way
"Software arcs" suffer from the problem that they are a series of
straight-line draws. The program does not give any opinion, as far as I
have ever noticed, to control the number of draws per angular measure. My
sense, though, is that the deviation would not be great; I'd be surprised
to see more than a mil.
But I haven't, for many years, looked at this. I do know that Protel, with
small arcs, draws an awful lot of very short segments and should not have
this problem. So it would probably occur with large arcs. A little
experimentation would show how Protel actually treats the arcs and what
the maximum deviation could be. It would then be easy to avoid the
clearance problem by creating the arcs a little oversize and then backing
them off to the final value.
I liked software arcs because they are easier to import across CAD
platforms, and the data can be more easily manipulated. The RS274X arc
command is a tad complicated....
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