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Trying to make a smoke box number plate. On the computer we made the design
sized it 5/8" diameter and the made the mirror image. Read several
sites about making printed circiut boards. It seams like they are printing on photo paper then with a iron transfer the ink to the copper. I'm using brass.
we could not get the ink to transfer. I would like to figure out this process
so i can make parts in the future. Any one have some advices or a process that works?
 

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Hi Chris,

The idea is correct BUT there is far more involved, as you must have a good resist - thats the black parts that are what is left, the brass is etched away with the (very nasty) chemicals. This leaves the parts that were black on your design, and they need half etched parts to hold the entire design together otherwise they fall into the liquid -NOT the intention!

Brass has various degrees of hardeness but all are harder (thus more difficuilt to etch - hence stronger chemicals) than copper.

PCB's being copper are realtivly easy, brass is not I'm afraid.

To get good edges and accurate design, you need to make the design at least 5 times larger than required; have a word with some commercial etchers to see what they need before running a proof etch.

They should also be able to give you some prices, a photo negative needs to be made from the design, including any extra colors (for etching from the back and also half etching either way). They shouuld be able to do that and tell you what size of sheet is reqwuired to fill their 'photo tool'; (don't forget that your original is up to five times the finished size) that is what your design ends up as.
 

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I've always read that one should print onto a transparency using a laser printer of photocopier. The laser toner is actually plastic, and it can be transferred (with heat from an iron) off of the transparency. I doubt you'll be able to get an inkjet printer to do anything useful for this process. With that said, I've never tried either method.

If your design is simple enough would it be possible to draw the mask by hand? I believe that Sharpie ink will work as a resist. I wouldn't want to make a lot of parts that way, but for a one-off, it might be easier than trying to print the design.
 

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I use transparencies specifically designed for ink jet printers. You can get them at staples here on the North Central Coast of California. You then add a photo active emulsion bought at most art stores. The instructions for using the emulsion come with the product and is a lot clearer than what I can describe. I don't know about the heat transfer technique, but it seems a lot easier than photo active emulsions. Does anyone have a vendor?
BTW. If you use photo active emulsions the black part of your transparency will be the stuff that is eaten away by the etchant,,, which is the reverse of what you will get from a direct transfer.
One thing about the photo emulsion, you have to have a very clean and polished brass surface or the emulsion will not stick. I'd imagine its the same for the heat transfer, but I won't know till I try it, so If you have some source you can provide me for this cool technique, I would really like to try them.
I suspect that if there is no source, I have an idea that the person etching this way is using the special ink jet paper for heat transfers to materials. That stuff is also available at staples. I'm not so sure the ink jet transparency paper will behave favorably to heat like the former product.
 

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I bought this photo-etching kit a few years back from micro-mark:
http://www.ares-server.com/Ares/Ares.asp?MerchantID=RET01229&Action=Catalog&Type=Product&ID=83123

Basically you print your work onto a transparency. Then you laminate photo-resist material onto the brass sheets (I think you can by this already done at other places). Then you take your printed transparency and clamp it over the photo-resist covered brass and expose it to the sun for a few seconds or under a special light for a few minutes. This process hardens the photo-resist material to the metal on the clear sections on the transparency. Then you put the metal sheet into a developer solution, which removes the unharded photo-resist. So now you are left with a hardend material on top of the metal surface that will not be eatin away when you put it in the etching batch.

Here's some photos of the project I was working on of an 89' enclose autorack in Z scale and some photos of some of the steps:
http://www.conrailray.com/testmain.php?scale=z&category=freight&page_id=8

-Ray
http://conrailray.com/index2.htm
 

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Steve,
Thanks, that makes sense now, seeing that the transparency is used for over head projectors and that surface is hot that they set on.
I'm still going to experiment with the T-Shirt Transfer material to see how that works, since it will probably be easier to use in the long run.
I'll let everyone know how that turns out in another thread as soon as I try it.
Ray,
That is exactly the process I use, except that I use photo emulsion because it is easier to apply and that resistive material provided in the kits can get very brittle and breakdown if you are slightly off on the timing to expose it to light.
 

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Here's another article on acid etching. While the area of modeling related too is about as far as you can get from railroading, it's still I think a very good bit of information. So for what it's worth here's the link.

Acid-Etching by David Merriman
 
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