Hi there,

Although not directly answering your question, more having a pop at your
failure to check the Gerber's before you send
them out & the subsequent recommendations on getting a Gerber viewer.

"Which one do I get" you ask.
Well this question pops up frequently, so here is a pre-prepared message
containing info on many
Gerber viewers etc.

Rather than just select a Gerber viewer at random, give your PCB
manufacturers a call & ask them what
software they use, and if there is a free viewer available.
It can be far better for you if you use a viewer that matches up with
the front end software used
by your PCB manufacturers.
If its not freeware then (providing the cost is not too great) a Gerber
viewer is well worth paying for.

I.E.
My suppliers all seem to use Graphicodes "GC-CAM", so I use the freeware
viewer "GC-Prevue" to view Gerber files.
I find it easy to use and very flexible in its ability to use many
different aperture & drilling tables, it allows
copying/merging of layers (& hence step & repeat), and can produce a
report on the number of drill hits per size etc.

Before sending any data to the PCB manufacturers I always check it, to
ensure that it is correct.
WYSIWYG is a fallacy (and don't we know it!).

Once I have viewed my Gerber's, turned invisible any pads etc that I do
not want on the photoplots (that my CAD system cannot),
I then send the saved GC-Prevue file to my PCB manufacturers instead of
the Gerber's.
They appear to prefer this, I know that I do.

I then get them to send me a copy of the step & repeated file before
they photoplot it.
I then view the data, checking that it meets the spec that was sent with
the original data etc.
That way I can be sure that the panel layout is correct & will suit our
production processes.

Now I do not want to be accused of being biased towards GC-Prevue
(although I am), I have tried many others
and am comfortable with this one though (especially as its free, so I
get updates whenever available.
However you could do the same sort of S&R checking no matter what
software as long as its the same as your PCB manufacturers.
(That's the main reason for this long explanation).

Here are some websites offering other freeware Gerber viewers that you
might like to try
GC-Prevue    http://www.graphicode.com
Viewmate     http://www.lavenir.com
CamCAD       http://www.camcad.com
CAM350      http://www.ecam.com
CAMCAD      http://www.rsi-inc.com (hang on, why have I got 2 entries
for this one?)
Valor Universal Viewer    http://www.valor.com  - Click on "FREE VUV"
A free Allegro Viewer is at
http://www.ambit.com/press_box/na/pr/1998/PCB/tsld005.html

Also for AutoCAD DWG/DXF file viewing you can try VOLOVIEW EXPRESS,
available via the
AutoCAD site or from ftp.autocad.com (its a 15MB download though).

For track width/current/resistance calculations try PCBTEMP available
freely from http://www.ultracad.com.
It can work out the track width for given current/temp rise/copper
width/thickness & visa versa.
Also the resistance of the track can be calculated.
They also do Crosstalk & transmission line calculators.


Matthew Lamkin
Printed Circuitboard Draughtsman
Protec Fire Detection PLC.



>-----Original Message-----
>From:  Mark Walter [SMTP:[log in to unmask]]
>Sent:  Monday, July 17, 2000 8:38 PM
>To:    [log in to unmask]
>Subject:       [DC] Cadence Allegro RS274x Artwork Bug
>
>Has anyone seen problems with generating artwork files
>using the Gerber RS274x Format on Cadence?  We are
>running version PE13 still and I recently sent out a board
>using this "new" Gerber only to find out that one of the
>shapes on the top layer did not plot- No errors nor warnings
>regarding this were given and the boards will have to be
>reworked at a considerable cost and loss of time in the factory.