DIY etch-o-matic

[electrosonic]

If you haven't seen it their website it here

http://www.etch-o-matic.com/index.html

I found a pdf of a DIY version of the same  idea here

http://dl.dropbox.com/u/30050282/electric_stencil.pdf

Here is some information about using a Saline Sulfate (copper sulphate + regular salt) solution to electro etch aluminum.

http://www.nontoxicprint.com/etchzincsteelaluminum.htm

Here is what I have done so far

I ordered some durafilm and through a bit of trial and error have figured out how to develop it without the $200+ uv exposure kit.

I had an old ikea halogen power supply lying around which puts out 12VAC at 5A and put a 12v 50W halogen bulb in series with that to make current limited power supply (limited to about 4 amps).

I put one lead from the power supply to a 1590BB, and put the stencil on the enclosure, and then some felt soaked in the copper sulphate salt solution on that and then a piece of scrap metal was put on that which is connected to the other terminal of the power supply.

The bulb lights up, some crackling noise is made and some heat is generated.

Here is the result.




The technique is promising, the lettering of "out" looks good, the rest not so much. I moved the stencil on the bottom labelling resulting in the "smudge".  

Electro etching should be safer than using ferric chloride, the saline sulfate solution it is less dangerous and the reaction is more controllable.

It might be fun to play with a mimeo stencil in this application. A quick search of Google shows this supplier

http://www.repeatotype.com/mimeo.html

Anyone tried anything similar? Any advice or hints would be appreciated.

Andrew.

[Craiz]

Extremely cool! Thanks! I'll definitely be trying this.

[fpaul]

I've been planning to try it but haven't ordered any stencils. 

I'd be interested to know if you can get consistantly good etches.

[defaced]

I had an old ikea halogen power supply lying around which puts out 12VAC at 5A and put a 12v 50W halogen bulb in series with that to make current limited power supply (limited to about 4 amps).

Is the halogen bulb serving as the rectifier too?

[electrosonic]

Is the halogen bulb serving as the rectifier too?

The halogen bulb just limits the current. I made a second box that has outputs for current limited AC and DC (I used a 6A, 200V diode bridge). I found the DC marks were less dark. Maybe I should try again to verify.

I didn't use the bulb assembly, I just soldered some thick copper wire onto the halogen bulbs pins. If it burns out I have to redo it. The bulb is inside a 1590B, with a hole drilled in it above the bulb so I can see if it lights. I find in practise the brightness of the bulb gives you an idea to how much current is flowing.

I am not totally sold on the durafilm, it is kind of pricey. The etchomatic site does offer free samples so I would recommend trying that.

Other options I am considering are StencilPro, kind of like durafilm but it doesn't use a developer, just expose to uv and wash with water.

Mimeograph paper, you could draw or trace onto this and electroetch through it.

Maybe laser cut vinyl

The reaction is less violent than acid etching so I think there are more options for the resist. I think you could use a Sharpie for resist if you wanted to.

The main thing is finding out a technique which gives reproducible results, which means trial and error. The markings are dark but not deep. So in this stage I keep sanding off the same enclosure and trying different methods.

Andrew.

[fpaul]

I signed up for the free durafilm samples about 2 months ago.  Never showed up.

[electrosonic]

Still trying to figure this out. Some progress,  here are some test etches of a crab drawing -



Not super clean, but is has potential. (I got lazy in sanding out previous attempts as you can see)

Andrew.

[defaced]

No love on seeing your pic.  What is your setup like?  Volts, current, current type (AC or DC) and if DC, how do you have it connected, anode to the work, or anode to the solution? With those parameters maybe we can help. 

[electrosonic]

No love on seeing your pic

Yeah I wasn't saying it was beautiful.

I have a 12 volt 4 amp supply, those etches were done using copper sulfate and table salt as an electrolyte. I am still tweaking the exposure time and developer strength for the uv stencils. I have tried etching with AC and with DC (positive connected to the enclosure) and I am not seeing any difference between the two.

I haven't seen anyone else on this using this technique for marking enclosures, so any help/hints would be appreciated.

Andrew.

[defaced]

Ok, cool.  I can see your pic now, so I have some more ideas.  I have never done this for this application, but have done electrolytic etching before so my comments are somewhat general. 

Since electrolytic etching is largely driven by current density (amps/unit area), and your etch looks darker on the edge and lighter in the middle, I'd gather to say that you have lower current density in the middle of your etch (assuming the resist was evenly distributed and such).  Since the intent with the type of etching is to burn the living crap out of the area to be etched, I'd try the following to get the current up:
Etch a smaller area at a time
Add more salts to the solution until it saturates thus reducing it's resistance
Add more voltage to the supply to help it push more current through the resistance

And as an off the cuff idea, I noticed that the concentration of hydrogen peroxide in my copper etching solution had a strong effect on etch rate.  I suspect this is due to it aiding in the removal of the non-conductive oxide layer created on the surface of the area being etched.  You may have luck adding it to your solution. 

Keep up the good work!  I have wanted to go where you're going with this for a while, but time is short, so it's nice to see the process being publicly developed for what we're doing.

[electrosonic]

One problem I have been having is the electrolyte tends to be drawn up between the stencil nd the enclosure, blurring the edges. The process creates gas which can bubble under the stencil, making it worse. There are a bunch of diy knife makers who brand their work by similar techniques, though I think stainless steel is easier to mark than aluminum. I tried adding black fabric dye into the electrolyte to see if the etch would be darker, but it made no difference.

My next attempt will use less electrolyte and in apply the current in short intervals to prevent bubbles from building up.  I don't know what commercial machines uses for an electrolyte when etching aluminum. Maybe I can find some MSDS datasheets online for some clues.

Andrew

[artifus]

make that 'bug' a 'feature'! looks cool to me. play to your strengths.

[amz-fx]

The electrolyte for aluminum electro-etch contains a significant amount of acetohydroxamic acid, n-fluoren-2-yl-, cobalt (2+) complex (cobalt salts), along with sodium salts and a wetting agent.

I suspect that the cobalt acid will not be readily available to individuals. The only commonly available cobalt compounds that I can think of are in vitamin B12.  There are some in LIon batteries but it is probably not wise to disassembly a battery for its internal chemicals.

So, what to try?  Maybe white vinegar, vitamin B12 and some table salt...  sounds like a homeopathic remedy more than an electro-etch!  This is just a wild guess as a suggestion, and I have no idea if it would work at all, or even if B12 is soluble in acetic acid (vinegar).

Best regards, Jack

[electrosonic]

I guess I will stick with the copper sulfate / table salt solution works well enough for now. I hadn't thought about a wetting agent. The electrolyte doesn't easily pass through the durafilm, maybe I need to work on that.

Andrew.

[garcho]

There are a bunch of diy knife makers...

Sorry, just had to make sure no one missed that.

[electrosonic]

I had no idea that people made their own knives (outside of prison I guess) until I started looking for electro etching on YouTube.

Andrew.

[Perrow]

I had no idea that people made their own knives (outside of prison I guess) until I started looking for electro etching on YouTube.

Andrew.

I've DIY'd knives, this for example:







It's supposed to hang on the left chest strap of my backpack when I'm out hiking. Just raise my right hand to my heart and grab it, sits perfectly in my hand. Not electro etched though 

Since I made it I've changed backpack and the strap on the new one is too wide to pass through the hole in the sheath