The Shop > Metal Stuff

Electro Engraving Problems

(1/5) > >>

vtsteam:
I've been trying to electro chemically engrave a small metal plate or my new lathe. Not much luck yet. I first tried doing a resist transfer using a laser printer image on paper.



To make the transfer sheet, following several how-tos posted on the net. For a transfer medium I tried printing on three different suggested papers I could find around the house: glossy magazine stock, the back of a sheet of labels, and some coated printer paper. The test piece was aluminum, which I sanded with fine sandpaper, then hit with Scotch Brite, and cleaned with alcohol.

None of the above papers transferred completely. The glossy magazine stock may have worked the best. For that trial  whitespace was removed by soaking the paper in water, and rubbing it off.

The other two were supposed to transfer just by peeling off without water. The label backing did not print well through the laser -- it was a little pale and blurry, and left an after image further down the page I didn't even try with that one.

The coated paper did a little better and it did transfer somewhat, but not well enough.

I don't know if the heat was high enough, or the pressure wasn't sufficient, but I was using a model airplane covering iron set to the highest setting, and spent a lot of time pressing very hard -- it just didn't print well.

I'm suspecting that maybe the laser toner itself is at fault. It's an aftermarket cartridge, so that may explain the difference I'm getting compared to others I've seen in videos. The normal printout on paper is somewhat light as well, so that may well be the culprit.

vtsteam:
So then following a second suggested method in a video, I pulled out of storage a small cheap 2.5 watt CNC laser engraver I'd impulse purchased a couple years ago for model airplane work. The YouTube suggested method was to paint the alumunum test piece with black spray lacquer, and then burn the design through with the laser. Afterwards you etch and then remove the paint with lacquer thinner.

Well, because the size of this plate was only 4.25 inches wide, the lettering is quite small. I had saved the working png file at 300 dpi to preserve detail. After doing a couple test burns of a few letters on the prepared stock, I found that I needed full 100% power, but shortest burn time for best results. So, settings known, I started a full burn of the image at 7:00 PM, and figured it might take over an hour. I was using the software bundled with the engraver, directly with the png file.

Nope. It took 5 hours -- I was just about to abort the burn so I could get some sleep when it finished at midnight.  :wack:

vtsteam:
The burnt image wasn't perfect but legible, and this was just to be a test piece anyway. Next step, etch. There are quite a few methods and recipes on the net for etching, but the one that appealed to me as probably being as effective as any, and using available non-toxic household chemistry was one that mixed distilled vinegar with table salt and the used electrolysis to effect the etch.

So I hunted up the ingredients and found a vintage variable power supply (a 1963 kit nicad charger) and a tall glass vase and some wires and tape. Taping positive to the workpiece, and negative to a scrap of aluminum, I was in business. It bubbled, and  looked suitably mad scientist enough to raise a couple of eyebrows in the household before dinner...... well maybe a couple of jaded shrugs. Luckily I owned the vase.

vtsteam:
Most of the online accounts of this type seemed to get a deep etch at about the half hour mark. I had periodically switched off the power supply to pull out the workpiece and check progress, also to help agitate and clear away bubbles. But after 30 minutes it didn't look like much had been removed, if any. The cathode plate had been bubbling vigorously, but the workpiece's etched lines were generating gas at a more sedate rate.

I decided to go longer. I had the charger cranked up to its highest setting. Though without a meter, I didn't really know how much current I was pushing. Or the voltage. I just assumed everything was working because of the bubbles.

After an hour, I thought I could see definite etching, so I decided to call it done before some of the delicate spaces inside the small letters got undercut.

The result after cleaning off with lacquer thinner? Barely etched -- some areas not legible. Afterwards I did check the voltage after reconnecting everything, and it was 1.25 volts, far below what most recommend (ranging from 3.5 to 12 V). I probably should have used my 12V car battery charger. Oh well.  :wack:

So, determined not to spend another five hours babysitting a CNC router, I decided that raster (pixel) graphics were probably not the best way to go, and I'd look into converting my image into vector graphics and ultimately a g-code file.

Well 5 (coincidentally) hours of research later I had converted the image to an SVG file via Inkscape, then downloaded and installed a gcode generating extension for the same program, then found a detailed set of instructions how to make the file conversion suitable for a laser cutter (modifying the plasma cutter tool setup) and finally finished the job! Not. The generated G-code would never have worked, I could see quite plainly in the tool paths. The problem was the tiny size of the letters. I'm sure it would have worked on bigger graphic images.

So finally, I'm back to square one. I think the best way to get this etched for this particular image is likely to be through the laser printer paper transfer method, not the cnc laser engraver route.

I will need to get a denser print with maybe Dell (or Xerox) toner on proper transfer paper and that means sending away for stuff. Unless of course anyone else has a workable alternative suggestion...

AdeV:
Hm, you've got me thinking now...

I bought a cheap Samsung M2026W laser printer for my experiments with PCB etching. Like you, I went through all sorts of pain trying to find a decent printable medium which would transfer well onto the copper board. I also struggled to transfer it well using an old clothes iron. As mentioned elsewhere, I ended up using a cheap laminator, which worked great for a bit, but then the overload clutch started spinning; so I had to remove that (or, rather, jam it up so it'd end up stripping teeth rather than clutching... it's worked OK so far! The printer I bought from Argos (a sort of sells-everything catalogue shop in the UK), the laminator came from Amazon.

The best stuff I've tried so far is laser printable vinyl, printing actually onto the vinyl surface itself. Pass this through the lamintor several times (to build up sufficient heat in the piece), and so long as I didn't get too impatient, I was able to get 100% toner transfer.

AS for the etching itself.... I was using a mixture of hydrogen peroxide and hydrochloric acid, both of which I appear to have lying around the workshop  :scratch: :loco: :zap: for my PCBs, and had some success, although far more error than trial.... for aluminium I'd use sodium hydroxide - drain cleaner - which I also appear to have "a quantity" of around here... Actually, I may even have some distilled vinegar come to think of it.... don't ask.

Anyway.... I'm going to have a go tomorrow I think, just to satisfy my own curiosity... and if it works, I'll put some photos up for you.

If we didn't live on different continents, I'd offer to print your design onto vinyl and post it to you (actually - I will offer to do that if you like, but I've no idea how long the post will take!).

Navigation

[0] Message Index

[#] Next page