|Dec 01, 2005, 02:30 AM|
Photo Etched parts
Do it yourself.
For at least the last year or two, I have told myself that I would make my own photo etched parts. And in the past, I have. I drew a triangular truss for a mast onto each side of a thin piece of brass with a sharpie marker, Threw it into some Ferric Chloride for etching circuit boards, and came out with an open web truss that I could solder onto my mast.
This time I wanted to do something a bit more elaborate. So I bought everything I needed to make a good photo etched mask, laminate it onto brass, and etch the parts at home. That was back in June (2005).
Well with the day mostly for my self, I cracked all the seals and followed the instructions from Starship Modeler.
I created the artwork in Coreldraw copy and pasted together a full sheet, 8.5"x11", and printed out onto glossy photo paper.
I added some small attachment lines, with a sharpie marker, across the artwork so the parts would stay together as on a model tree.
This was then photocopied onto "Press 'n Peel" transfer film.
the Transfer film allows the photocopy toner to be laminated onto the brass sheet.
The brass is cleaned, and then the brass and the transfer film are run through a laminator, or pressed with a laundry iron.
|Dec 01, 2005, 02:41 AM|
I ran the sheet twice with the cover sheet over it, and found that there was not enough heat to bond the toner to the brass. I ran the brass and the "peel 'n press" through three more times without the cover sheet and was satisfied with the adhesion.
At this point I roughed up the back side of the sheet with steel wool and primed it with some standard Krylon primer. As mentioned in the "Starship Modeler" article, red primer would have been a good visual for when the etching was finished. I used what was on hand.
Once the primer was dry, I protected it from scratches with clear packaging tape. This also holdes the parts together after etching.
I then cut away the parts that I wanted to try etching.
|Dec 01, 2005, 02:53 AM|
The "Peel 'n Press" backing is then removed. I actually laminated the smaller piece three more times. When I started to lift the PnP backing, some of the toner came up. Three more times through the laminater was sufficient to keep everything in place.
A good photo copier is really a must. The copier here had a "streak" through the art work. I noticed it on a test copy, but went ahead and copied to the PnP as this would all be good information.
When the PnP backing was removed, you could see bare brass where the photocopier had streaked. I touched up these and other areas with a sharpie marker.
Once I was satisfied I also blacked out any other exposed brass that I didn't need etched. Then it was off to the acid baths.
|Dec 01, 2005, 03:11 AM|
The garage was cold, so I brought the tub into the house after the first half hour.
I agitated and flipped the brass about every half hour.
After the first hour and a half I could see the primer showing through the brass.
This is where the red coloring would have been helpful.
I allowed the piece to etch a full two hours. I then rinsed the piece off and checked all the etch areas for the primer color. And declared the piece done.
I rinsed the piece thoroughly in a solution of baking soda and water to neutralize the acid.
The 1/32nd inch line work was eaten through from the edges in some areas, but the 3/64 inch lines were almost perfect. The areas to be etched don't need to be so wide, most of my "etching" areas were at least 1/32nd inch wide also, and I think they came out a bit large.
The toner will wipe off with laquer thinner. I actually bent a piece by pressing too hard. Interestingly, the areas that were covered with the Peel 'n Press toner application were slightly etched, and copper colored. Areas where I had marked with the Sharpie marker were actually better protected, and still shiney.
To release the parts from the tape you want to soak them in laquer thinner. I tried peeling the tape away dry, but it was difficult. With a little soaking, and a quick wiping to remove the residual primer, the back side was also a shiny brass tone.
The large parts are supposed to be a louvered vent for the fireboat.
The smaller rectangle frames will have mesh stretched over them, and be railings for the Washington State ferry boat.
|Dec 01, 2005, 08:22 AM|
By building an warmed and agitated bath (aquarium heaters and bubblers have been used), you get a much faster etch, with sharper resolution.
Also decrease time in bath by etching from both sides. Simply reverse the art to make two Press'n'Peels sheets that can be put together, toner side to toner side. Register these PERFECTLY by sighting through, and tape one edge to make a sandwich board. Then slip the brass sheet in between, and proceed to the fusing step.
And lastly, by including little connector tabs in your artwork, you can ensure that loose parts don't fall out and get lost.
|Dec 01, 2005, 12:21 PM|
I had the bubbler, from an old aquarium, but kept imagining sputtering and splashing acid. When I brought the etching tub into the house, I put the cover over it, and sat it on top of one of the furnace vents.
|Dec 03, 2005, 11:52 AM|
Joined Jul 2005
Back about ten years ago, I got a book from the local library as to how to do the same thing you are doing. Although I used the method, supplies and equipment noted in the pages, I can see a similarity of a few items on a more modern scale. Maybe I can aide you on your next project with a couple comments.
I was aiming to etch some .015" and some .020" brass sheet that I picked up at a swap meet for $1. I initially went the route explained by the brochure obtained at the electronic shop for making Printed Circuit Boards at home. That was enlightful but a waste of $$ for the system essentially only marred or darkened the surface, and did not really cut brass. It was set up for cutting copper, not brass. Months later, I then found the book and went the route of silk screening. Got a quart of resist for Nazdar of Los Angeles, and a whole bunch of other things. After setting up, this portion went like automation, and produced very fine lined work.
Leaving that phase asside, the biggest problem was in actual etching. Went through a lot of brass sheets, and chemicals, systems etc over the summer until a system was developed. You are probably near a good system, but here are some end results that was found.
Before applying the resist, scrub the brass. Do not rely on solvents. Initially use liquid Dawn detergent, mixed with some kitchen cleanser. Scrub this in with a nylon pot scrubber. need to get rid of any surface oxidation present. When you rinse off the solution, besides being shiney, but not glossy, water ought to quickly sheet off into one corner and not make visual pools. Keep your own hands squeeky clean, hold only via the edges, so as not to leave any fingerprints. Then use a simple strong solution of Tri-sodium Phosphate to de-grease. This is available at house paint supply stores, not Home Depot for about $2 per bag. You should see very tiny microscopic and random scratch marks across the surface. Not your smiling face.
Don't use a plastic tub. The bottom is too irregular. It will resist the acid, but the little lumps and bumps will also distort the wave action of the moving etchant. I got a Pyrex glass cooking pan from local swap meet. It was nearly dead flat across the bottom.
Don't etch face up. Etch face down. So that etchant would flow underneath the brass, I just bent each of the four corners a bit to provide a "Leg" to stand upon. Thus the very fine brass fell away from the surface via gravity, and did not instead lay on the surface, and hinder the further action of the etchant solution. When done and you carefully lift the parts away, there ought to be a silt of brass lying on the bottom.
Instead of the bubbling action mentioned for agitation, I found another $1 item at a swap meet. It was a 120VAC gear reduction cranking mechanism. It turned at about 1/2 RPM, and I simply drilled a hole for a coat hanger wire to insert and duct taped the other end to the Pyrex bowl. This provided a rocking motion to the etchant solution, as trying to pump it would mean an acid resistant pump. Expensive.
The standard Ferric Chloride that is obtained from Radio Shack or other electronics places is designed for copper. Not brass. A chemist friend of mine suggested that I hop up the solution by adding some Hydrochloric acid. I got a pint of this at a chemical supply place, (yes had to sign a form stating it would be used for legal purposes only) for a cost of about $2. I mixed it in at a rate of 4 parts etchant to 1 part acid. And BOY! did that ever change the cutting rate. It went from a two hour job to a 20 minute job. Did not have to warm up the solution either, the hot summer sun out on the back patio made it good enough. I turned on the wave action motor, poured in the hopped up solution, and then could litterally see chunks of brass fall away from the surface. Although they looked big, in the end it only etched a mere 0.002" into the face of the brass.
When done, wash off all residue the the remaining solution of Tri-sodium phosphate.
Initially, the Radio Shack stuff cost me about $20. Afterwards, omitting this expense, I got it down to about $15 with materials that worked, and took less time. But, that took time and was a learning experience too.
|Dec 03, 2005, 12:12 PM|
Thanks for the excellent info Umi & Coosbay. Can't wait to try this some time!
When working with the photoresist don't you have to expose the areas you want etched with some sort of UV lamp or am I confusing things?
|Dec 03, 2005, 12:53 PM|
From my earlier experiences, I knew to keep the etch side down, and I set it on some spacers to keep it from sitting on the bottom. I actually wanted to stand it on edge, but didn't want to pour all the etchant into the tub for the first shot.
I may build a plastic rack that can hole the pieces on edge when I do the next few.
It will also allow me to do a several at a time.
Also as Pat mentioned, it is possible to etch from both sides, but I didn't trust myself to line up the 1/32" line work.
One of the other guys in the local boat club does "photo" etching. You can pick up all the supplies in a kit at the "better" electronics shops. That's "Norvac Electronics" here.
The kit comes with a coating that you apply to the brass. Once that is dry, you lay your artwork, printed on clear acetate or other transparent media, over the coating and expose it to UV. My friend says any lamp will do. This is where it gets backwards.
Any area that is clear will expose the coating to light and harden it. These hardened areas will remain when the coating is later rinsed off. This is where your part will be protected from the etchant. I wasn't sure about the "regular" lamp exposure and my "fish tank" friend said he had a UV lamp for water purification, but that it would also give you a tan. So I opted for the toner method.
If someone wanted to try a simple part, the sharpie marker on brass does work pretty well.
Thanks for the "hop up" tip on the etchant. I will check into that.
|Dec 04, 2005, 04:26 PM|
Istanbul / TURKEY
Joined Feb 2005
more sppedy etchant solution:
Hydrochloric acid and controlled mix of hydrogenperoxide (H2O2) speeds up the etching time,
I prefer face up etching, if it is faced down, sometimes air bubles sticked to some fine corners, details and blocked the etching process
best for the bath; I use photo paper trays used for development (darkroom equipment)
|Dec 05, 2005, 01:39 PM|