Hi Guys,
There is an on-line users guide
at;
This has some good explanations and definitions of
RS-274X parameters as well as RS-274D "D" codes.
I used it as a reference when trying to get legacy
designs into Protel from Gerber. Protel will not accept standard RS-274X so you
have to manually manipulate the files to import them in the proprietary Protel
format, oddly Protel exports in standard format. This is a clever marketing
strategy which makes it as hard as possible to transition from one CAD/CAM
package to another (he said with sarcasm dripping from his voice).
Dan
----- Original Message -----
Sent: Monday, January 27, 2003 6:14
PM
Subject: Re: [TN] Aperture file
format
Hi Phil!
Here's some stuff I found that explains
more what a *.whl file is. I've run across them quite a bit, and turn them
into a text file to import as a aperture list to view the gerbers...I use GC
Preview, and Lavenir Viewmate.
Hope this helps...
-Steve
Gregory-
Gerber
Gerber is a
format designed by Gerber Scientific for use with their
Photoplotters.
The Printed Circuit industry has adopted it as a
standard because of the flexible and reliable way in which it can be used for
Photo plotting Printed Circuit artworks.
The Basics
Gerber data contains all
of the X & Y coordinates of pad positions and the coordinates for the
start and end of traces. These are preceded by codes to tell the photoplotter
what it should do with these coordinates.
The two most common
instructions are "Flash" and "Draw". To understand these terms it is useful to
know a little of the history behind photoplotting.
In the early days a
photoplotter consisted of an Ultra Violet light source which could be turned
on and off at will, these are called Vector plotters.
The light from
the source would shine through holes on the aperture wheel to expose the UV
sensitive photographic film. These holes are known as apertures and depending
on the size of the wheel only 50 or so apertures could be used.
If more
apertures (pad or trace sizes) were required from the design another aperture
wheel would be needed. The process of the light turning on and then off
through the aperture wheel in a certain position is known as a Flash
.
To produce a trace the appropriate aperture would be chosen and the
light would turn on and remain on whilst the head moved around drawing the
trace, in much the same way as a conventional pen plotter would do, this is
known as a Draw.
This is obviously a very time consuming process, some
plots could take in excess of 1 hour, also designers became very limited by
the number (and shape) of the apertures that they could use.
To combat
these restrictions Raster laser plotters were developed. The way in which
these machines differ is in the way the film is exposed and the data handled.
Before the Gerber data arrives at the Photoplotter the circuit design is
converted into a series of dots or Rasterised.
Then instead of the
aperture and light source arrangement as used by the above plotters a Laser is
used. The Laser turns on and off very rapidly where the dots are required thus
exposing the film. The Laser normally moves from left to right in strokes down
the sheet at very high resolutions 3-5000 dpi , a 20" * 24" sheet being fully
exposed in less than 6 minutes.
Because the data is converted into a
series of dots and no physical aperture wheels are used any shape can be
plotted with no limit on the number of apertures that can be
used.
Formats
RS274-D.................Requires a separate aperture
table
RS274-X..................Aperture table is embedded in data.
Hello Technetters,
I've come across an aperture file that
I'm having trouble reading into
my CAMtastic 2000 software.
Looking at
the file with notepad it has reference to CADAM (40) and has
the file
extension .whl
Can anyone shed some light on what this
is?
thanks,
Phil Dutton
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