I spent the day experimenting with a new process yesterday, Electroetching Aluminum. I had good results, but want great results. Probably half of my problem is the K40 I’m using to etch the masking material.
I tried Enamel paint, with decent results. The paint was very fragile in the areas that were thin.
Next up was Lacquer. Faster drying than enamel, same issue with loss of detail and fragile thin areas.
Blue Sharpie. Total fail. Oddly I was expecting an effect similar to anodized aluminum. The laser didn’t even touch it!! I’ll try again with a black one once I find one.
Powder coating yielded the best results. Quick cure time. Decent detail. it takes 3 passes on the K40 to completely ablate the material.
Anyone have any thoughts on other materials that may work well. Either a direct coating that can be applied to the surface, or an indirect stencil film?
Polymide worked so poorly I forgot to mention it. maybe it was my settings, but it just charred. I have a large roll of Kapton from my 3d printer I was hoping to use, since I don’t use it for 3d prints anymore.
I’ve done some masking with polyimide tape for powder coating and it works OK in my opinion. The method I used was to cut out the shapes I wanted to paint and then weed them out before coating. You’re right, it basically turns to ash… black fine ash. Another problem I have is that it tears so easily it’s a huge pain to weed and then it’s a huge pain again when you’re peeling up the masking. Features wider than… say… 5mm are OK, but ~1.5mm wide and smaller are really annoying.
I can’t remember if I’ve tried engraving away the polyimide. I have, however, washed a piece of aluminum that had masking on it and the mask held up basically perfectly, even with gentle scrubbing with a toothbrush. Perhaps the char could be washed away?
I would like to try this stuff from Eastwood… http://www.eastwood.com/high-temp-blue-masking-tape.html
I ordered it last weekend, but the order fell through (their payment system didn’t like my shipping address/IP address mismatch and I didn’t like that they took two business days to let me know and refused to increase the shipping speed to compensate). Once I’m not mad at them any more I’ll probably order it again.
This tape is polyester and apparently withstands temperatures up to 500ºF. All the other polyester tape I could find maxed out at 400º. A quick internet search revealed that polyester laser-cuts and engraves quite well, but I haven’t tried it and I didn’t check many sources. The other high-temp polyester tapes seem to use a silicone-based adhesive, silicone also cuts and engraves well (as I understand it). Though, it doesn’t look like Eastwood lists the adhesive type for the tape being sold on their site.
Is the aluminum anodized? If it is, then I’m not surprised you had difficulty. The dry moly/cermark works by forming an oxide layer when lasered. If the aluminum is anodized, it already has an oxide layer.
On the other hand, if the aluminum is anodized, you can mark it by zapping the oxide layer. You just have to know.
(Technically speaking, all aluminum is anodized, because the way it resists corrosion is by forming an oxide layer – the oxide is the same “size” as the metal, so you don’t get cracking as you do with other metals, and once the layer is formed the metal is protected. In practice, however, that layer is only a few atoms thick so from a marking point of view it’s meaningless.)
So I revisited Kapton tape today. It looks like it may be a winner after all. The trick was 2 passes. One at near 100%power and 150mm/sec next pass at 100/200, it’s possible a third would have been helpful to remove the remaining adhesive, I used an abrasive powder, and dishwashing soap to remove the light residue that remained. The tape held up well, and the engrave is pretty clean, although some of the serial numbers we lost.
Did you find out what went wrong with the serial numbers? It looks like some mask remained in the missing part of the “1”, did the laser just fail to hit that spot hard enough, or did something happen during the washing phase, or something else entirely?
Was the abrasive powder Comet or Ajax by chance? That’s what I use to prep my aluminum.
Be careful with those cheapo number sets. I bought several in different sizes and in every single box there were several punches that had the number way off center. It is super frustrating to try and line them up only to have the result look like you were drunk.
In contrast I have a couple high quality vintage sets that I got off ebay and they are all perfectly consistent.
maybe it was my settings, but it just charred. I have a large roll of Kapton from my 3d printer I was hoping to use, since I don’t use it for 3d prints anymore.
