Author Topic: Brass Etchings  (Read 10857 times)

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Offline karlgalster

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Brass Etchings
« on: 02 February 2010, 18:47:11 »
I have never done any brass etching and I expect there are many others on this forum in the same boat (if you wil pardon the pun). Perhaps you and Mark should start a new thread on this subject?
Robin

Offline colin

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Re: Brass Etchings
« Reply #1 on: 03 February 2010, 06:05:09 »
your request in my command... shall i leave it under "General Discussion" or would it be better under "Hints and Tips"

in this thread, mark (hopfully) and i shall try and give a few tips on how to prepare a drawing so as you can get your own Brass Etchings done.

i have not got my own Etching chemicals, i just do the Drawing and then send the drawing of to some one who can..

Offline colin

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Re: Brass Etchings
« Reply #2 on: 03 February 2010, 08:01:08 »
First of all you need a Drawing program, I use Coral Draw, its reasonably easy to use, not as expensive as most CAD (computer aided drawing) software, and can save the Data into various Data formats.

then you need to find some one that can do etchings, and ask them at the same time what etchings process they use (Positive or Negative) and also very important what Data formats they except.

Q "what does Positive or Negative mean"

I hear the first question, there are two ways to etch and this depends on whether the metal has a positive or negative photo film on it.

if the film is positive you can do all your drawings in Black (remains) white gets etched away, of course negative is visa versa.

When doing your drawing, one of the simple rules to follow, no lines are meant to be thinner than the metal thickness your etching.

Now you can do your drawing, but thinking about that, when etching, both sides of the metal get etched at the same time, so you need a front and rear side, were the rear side is a mirrored version of the front side.

And if you would like things like nuts and bolts to stand out (relief) (2D / 3D effect) then careful thought needs to be taken as to which parts of the front side needs to be omitted, as the rear side is always the full picture.

So that would mean that the rear side is always flat and the front side now has indentations, if you would like the 3D effect that both sides of the object have indentations (relief) then you need to draw two fronts and two backs, or used the folding technique.

The following photos, show a boarder front and back, plus my version of turnbuckles were the top turnbuckle gets folded over the bottom turnbuckle, this giving a turnbuckle that is 0.4mm thick, but the bolt part is only 0.2mm thick.
« Last Edit: 03 February 2010, 08:12:07 by colin »

Offline karlgalster

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Re: Brass Etchings
« Reply #3 on: 03 February 2010, 17:55:28 »
Thanks Colin, not sure I totally understand this. Not sure I have grasped the idea of a 3D effect. Metal gets etched away both sides - is the 3D effect achieved by limiting the time the etching occurs? I can understand that having a mirror image the other side will give maximum thickness, just a masking one side then presumably that side is unetched the other side gets etched but what stops the etching from the other side eventually removing all the mertal unless the process is stopped after a period. Might help if I knew what a turnbuckle is?
Robin

Offline colin

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Re: Brass Etchings
« Reply #4 on: 03 February 2010, 18:14:53 »
the exact time that a piece of metal is emerged in the etching bath i am not to sure of.... that you would have to ask an expert in etching.

but both sides of the metal, are treated in the same way a photo is made (old style) with light shone through a negative onto paper, in this case the paper is the treated metal.

the 3D effect is achieved through placing two etched parts once etched back to back, and then either soldering or gluing them together.

below is a photo of a original turnbuckle, the etched ones, i will get a photo over the weekend from the person that is etching them.

Offline karlgalster

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Re: Brass Etchings
« Reply #5 on: 03 February 2010, 19:05:02 »
OK no timing involved. Still not sure about this. You said -

"Now you can do your drawing, but thinking about that, when etching, both sides of the metal get etched at the same time, so you need a front and rear side, were the rear side is a mirrored version of the front side."

OK understood.

But -

"And if you would like things like nuts and bolts to stand out (relief) (2D / 3D effect) then careful thought needs to be taken as to which parts of the front side needs to be omitted, as the rear side is always the full picture."

I thought the rear side was a mirror of the front side. If the front isn't a mirror image won't all the metal get etched away from the front?

Robin





Offline colin

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Re: Brass Etchings
« Reply #6 on: 03 February 2010, 19:20:18 »
when i draw something. like the above Turnbuckles, i draw the hole thing fist, replicate the amount i need, and then i mirror it, that is then the rear negative(photo) finished.

then i go back to the front and start rubbing out the parts that don't need to lets say 0.2mm thick, this then achieves the relief effect (2D)

then if two of these parts are glued back to back then you have 3D.

each side gets etched at the same time, lets say, 30 Sec etches away 0.1mm
with a metal sheet of 0.2mm it will be etched through in 30 Sec.

so with the film on the back the hole object says, the missing parts that were or have been omitted from the front will be etched away.

so the main object (rear side) will now be 0.1mm think and the front the parts that were left on the film will be 0.2mm thick

of course things like Doors, and the such like, on the front side you would removed the door and leave the handels, hinges and the likes of, this would mean you have a Door that is 0.1mm thick (from the rear negative(photo/film), on top of the door is the handels, window and hinges from the front negative(photo/film) which makes up the thickness of the metal to 0.2mm.

i hope this might have explained it a little better.  ^^^
« Last Edit: 04 February 2010, 07:03:11 by colin »

Offline colin

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Re: Brass Etchings
« Reply #7 on: 04 February 2010, 08:20:42 »
lets see if this photo might help....

if the piece of metal was 0.2mm thick, everything that is Blue and Green would stay at 0.2mm thickness
everything that is Orange, would get etched away on one side but remain on the other, so this would be 0.1mm thick once etching is compleat.
the pink is depicting the holes were at a later stage, once bent into shape and the rollers (green) are placed into position a rod can be inserted so that the block will work.

Offline karlgalster

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Re: Brass Etchings
« Reply #8 on: 04 February 2010, 18:40:39 »
Ok now I understand. I guess the timing must be quite critical to achieve etching from the original 0.2mm down to 0.1mm. Thank you for your efforts Colin in shedding light on thsi subject. I expect there are others out there who are also learning something but too shy to comment!

Got a few questions though. On your latest photo for example the artwork shows very thin lines on front and reverse. Presumably this to create something like spru that is cut off after etching?

How thin a sheet of brass can you use? From one of your earlier posts you implied the width of the "to remain" cannot be narrower than the base material width.

You get your photo etching done for you. What level of cost does this involve.

Robin

Offline colin

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Re: Brass Etchings
« Reply #9 on: 04 February 2010, 19:30:23 »
yes the very thin lines are a type of sprue that holds the items in place while etching and supports the items for transport, and of course cut off when you take the items out of the frame.

not only brass can be used, there are a few metal types that can be used but that is a matter for the person that is doing the etching.

as far as i know most etching can be done on metal that is 0.1mm to 0.5mm in thickness, the person that is doing my etching normally etches at a scale of 1:200 his website is only in German, look on the left side for Fotoatzteile 1:200      http://www.modellschlachtschiffe.de/shop/

when drawing lines, they have to be no thinner that the thickness of the metal, so if the metal is 0.2mm non of the single lines drawn can be thinner than 0.2mm, this only applies to a line that is on its own eg. the sprue lines.

the costs:
one of payment for the production of the negative (photo) film = between 10 and 40 pounds depending on the size of the negative (photo) film, a piece of paper size would in the region of 40 pounds.

for the etching anything from 3 to 20 pounds depending again on the size of the outer frame

for example the small blocks and the turnbuckles (total of 120 Items) will cost me about 30 pounds.
« Last Edit: 04 February 2010, 19:34:09 by colin »

Offline Mark

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Re: Brass Etchings
« Reply #10 on: 05 February 2010, 08:05:52 »
I am a bit late in getting into this thread but here goes.

I have never done any etching myself, but have been reading up on it and learning rapidly as I go. The basics as I understand it so far and the route I have chosen to follow are;

1. Draw the part/s (For which I used 3D CAD, this allowed me to design the sheet metal then "Flat Pattern" it) see below.
2. Produce the negative for the photo etching, this is where I think I am doing something slightly different. I am planning on one sided etching through 0.2mm sheet. To get the 3D effect I am producing a double mask. 100% protection means the photo resist Will be exposed fully to allow the material to be burnt away completely. 50% protection means the photo resist will only be exposed for half the time which means the etching process will go much slower and not eat all the way through. I have not looked at double sided etching on my first experiment as I did not feel there were any parts I that I needed reverse detail on.

This is a far as I have got, but hopefully will soon have something ready for etching.

Mark
« Last Edit: 05 February 2010, 08:17:43 by Mark »

Offline karlgalster

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Re: Brass Etchings
« Reply #11 on: 05 February 2010, 18:29:40 »
Colin. Interesting web site. As you said a lot of material at 200:1 but of interest as a reference for Kriegsmarine builders. I did notice they have a nice100:1 Destroyer radar matrass that would look good on the DM Z37.

The costings you quote are quiet high but you get what you pay for.

Mark,
I like the "flattening" feature of your software. The d.i.y etching approach is very interesting also. It will be informative to see how you get on.


Robin

Offline colin

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Re: Brass Etchings
« Reply #12 on: 08 February 2010, 11:46:36 »
jup that matrass does look rather nice doesn't it... :)

about the costs, the film production is the expensive part, once that is done the parts can be reproduced again and again, at much lower costs, for example if i require the 120 parts a second time it will be about 8 pounds..

Offline Mark

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Re: Brass Etchings
« Reply #13 on: 09 February 2010, 09:42:47 »
I have had a chance to sit down and finish the drawings for all the etch components now and have dropped them into a frame.

I will move things around for the next few days until I am happy that everything is supported.

Mark

Offline Mark

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Re: Brass Etchings
« Reply #14 on: 23 March 2010, 19:01:06 »
Well as usual work got in the way, but I have now finished the artwork. The company I am using has checked it all through and say it's ready to go. I have attached some pictures of the artwork and will post some of the etching when I get it back.
 
 
Mark
« Last Edit: 23 March 2010, 19:01:49 by Mark »