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EJ, I should have made myself clear, I wasn't suggesting that Corel was a CAD program, only highlighting some differences.
I learned AutoCAD way back in the 80's. Wasn't impressed with it. Tried again in the 2000's, still didn't like it. I've been using CorelDRAW for over 20 years. I won't say it is perfect, far from it, but I find it very easy to use. I like it better than Illustrator, probably more because of familiarity than any real advantage. The biggest thing for me is drawing WYSIWYG. I like being able to draw a square in one motion, fill it with black or a colour, turn it on or off via layers, copy OR duplicate it with same properties and know it will print as I see it. I've always had a problem with CAD programs that print after a line, to a line and you don't see what you've done until it's printed. I also like being able to switch from line view to full colour view with one click. Like I said, probably more a familiarity thing than an actual function of the program. I'm trying to learn Rhino3D and am running into the same issues. I just don't like how things are done.
As for accuracy, I draw to a half thou, which in my books is plenty for photo etch. When the chemical milling (photoetching process) is done, a second here or there can alter the outcome by that much.
So lets discuss the processes. Originally, Printed Circuit Boards were designed by people sticking black tape onto clear acetate 3 or 4 times the finished size. Then it was photographically reduced onto a negative or positive film (depending on the type of resist chemical), This had the effect of reducing any errors or roughness in the edges. Then the film was laid on a board with copper on it coated with photo resist and exposed to UV light until the resist weakened, allowing a developer to dissolve the part not wanted. After this the board was then dipped in Ferric Chloride acid, eating away the bare metal until you had resist covered traces left that would carry the current between board components.
Advances over the years included a resist film that could be stuck to the boards, instead of a liquid spread onto it to cure. Conveyor style spray washers to control exposure time of the metal to the acid, double sided boards, multi layered boards, CAD printing of the artwork to be photographed, then CAD printing onto the film and finally CAD printing of resist directly onto the boards. There were some other variations along the way, but these are the major steps we're interested in.
The process of etching metal without the substrate needed for printed circuits is essentially the same and is often referred to as chemical milling. Brass is generally used for PE because it's easy to manipulate and takes glue and paint well and is also solderable. Stainless is used when you want strength, but doesn't hold paint very well. Beryllium Copper is also used at times.
When I started doing my own PE for my kits, I preferred drawing in Corel since I was skilled with it, however, over the years certain technologies have disappeared or are difficult to find. One of these essential to the traditional method of PE making is the large format film cameras used to make the negative or positive films to use in exposing the resist on the metal. In the past, you could print on paper and have it photographed. Now that most places have gotten rid of the their cameras, you have to print directly onto a clear sheet with a special printer. Some places don't even like that as the sheets are thinner than they prefer to work with and could cause issues during the exposure. Most etching places are only set up to take CAD files and use these to print their own films or directly onto the metal. CAD programs set up for printing a little differently than Corel.
My preferred method is to export my file into a PDF, send it to a graphics place that still has a film printer and then have that film sent to the etcher. There are many other ways to do this. I like it this way as I know that what I see in the PDF is exactly what will be printed onto the film and nothing in the original file will be altered or misinterpreted.
Corel as been able to handle pretty much anything I throw at it size wise, but it has been known to crash on occasion.
Darren
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Darren (Admiral Hawk)
In the not so tropical climate of the Great White North.
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