At 08:33 AM 10/18/01 -0500, Robison Michael R CNIN wrote:
>my question:  what am i likely to find when i go over there?  i'm
>going to assume that there is some scanning or photographic
>hardware thats associated with some software program that
>converts a raster image into the vectorized gerber files.  are you
>guys familiar with this kind of setup?  what are some of the software/
>hardware setups employed for this?  surely its better than me sitting
>here re-creating the boards by hand.

I did a board by photographing the board, scaling and filtering the photo 
appropriately with Paint Shop Pro, and using a bitmap converter (there is 
one in the filespace for [EMAIL PROTECTED]) to bring the images 
into PCB, on mech layers. It was quite dirty, but I just used it as a 
template to place the traces.

However, software to convert bitmaps into gerber has been around for a long 
time. My guess is that the software analyzes the image and produces gerber 
draws and flashes to imitate reasonably closely the original. It will be 
great if it does this. If, instead, it creates a raster image with gerber 
draws, you would be able to use it as I used my photo, only the dimensional 
accuracy would be pretty easy to maintain.

Assuming that it outputs real draws for traces, you will import the Gerber 
to a working layer. You may need to clean it up, you might edit traces to 
be the same size that might be slightly different in the conversion. If 
pads have been built with draws, it will be a nuisance, because you will 
need to get rid of them. In fact, it might be simpler to just use the 
scanned data as I used a camera image.

You will identify common footprints from the layers; you may use your 
library for that; but for unusual footprints you will create pads from the 
gerber data if it contains flashes. You might or might not adjust their 
position; if a pad already exists, you will probably edit it to multilayer 
and put a hole into it, as well as giving it a number. Before doing this, 
select and copy a footprint's set of pads into the footprint editor. Once 
you have made the footprint, place the footprint over the pads you selected 
and clear the selection. This way you work through the board assigning 
components as appropriate and then deleting the free pads from your import. 
Eventually you will be left with only footprints and connecting track. This 
track may need to be adjusted, but redrawing it with loop removal turned on 
may be faster.

I recommend keeping the image on a mech layer so that you can, at the end, 
use a blink technique, or contrasting colors with alternating the layer 
drawn on top (or transparent colors so that non-coincidence will produce 
contrasting colors, like white for coincidence and two contrasting colors 
for primitives that exist on one layer and not on another), to compare your 
final layers with the input layers from the scanner.

You will probably also need to massage the gerber into a form that Protel 
will properly input. This has been discussed many times and recently, so 
I'm not going into that now.

Abdulrahman Lomax
Easthampton, Massachusetts USA

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