Acid cutting sheet metal


#1

I’ve been thinking about cutting metals recently, stainless, aluminum etc. It’s long been established that it’s not possible to cut metal with a 45w laser cutter, but I’m not one to turn down a challenge! :slightly_smiling:

I’ve etched PCBs in the past and, while it’s not possible to etch the copper surface with a laser cutter, it’s possible to use a laser to selectively remove a resist coating and then etch the exposed metal away with an acid. It got me to thinking, would the same be possible with 1-2mm sheet metals?

Granted, the copper on an FR4 circuit board is incredibly thin, but after searching I stumbled upon processes like deep acid etching which can etch thicker stuff. I’m wondering if anyone here has any experience with processes like this and if they’ve ever tried to etch clean through a piece of thin sheet metal. I’m happy to admit I’m pretty ignorant of metal etching processes, so I’d love someone to tell me why this is an awful idea, at the very least it’ll be a great learning experience


Lighting Gobo(s)
#2

It is a fine idea, and is a very common technique for jewelers and metal workers in general.
Straight acid etching works well as does electrochemical etching.
Here is a reasonable primer on etching http://www.ganoksin.com/borisat/nenam/etching.htm
It is an easy thing to experiment with, and you don’t even have to wait for your Glowforge!
Just make sure you have good ventilation and long gloves.

One thing to keep in mind, the deeper you try to go, the more undercutting you will get, so it is usually reserved for thinner stock.

Have fun!


#3

The link that @jkopel provided is a good resource. I would add a detail not mentioned;
When mixing the etchant or mordant always add acid to water, never water to acid. Acid is denser and will sink into the water, where adding water to acid will cause the water to “dance” around on the surface in a reaction similar to boiling that can and will splash it around.
Eye protection, gloves and positive ventilation are a must.

As the link advises, fumes must be exhausted, or done outdoors, with attention to where you stand in relation to the breeze. Be upwind.
The reaction causes gasses to be liberated and they tend to cling to the metal, preventing the acid from contacting the surface.
The author suggests using a feather to brush them away. A piece of string will do, or any nonmetallic soft material. I have used an eyedropper to squirt the submerged area to remove bubbles.


#4

Not to digress from the serious, technical nature of this thread, but acid eating metal just takes time. Makes me think of the Mythbusters’ salsa jailbreak episode.


#5

Undercutting was something I was concerned about, I was curious exactly how much undercutting would happen, presumably the longer the material stays in the acid, the more undercutting will happen. Perhaps using two mirrored resists, one on either side of the material, would reduce the amount of time required to etch, and therefore reduce the undercut.

It seems I may have to experiment a little with this, I’ll run a couple of tests with photoresist instead of laser-etched resist when I get some time and see if I can write up the results, it might be helpful for glowforge owners to be able to hack their way to cutting sheet metal.


#6

Thanks for the tip on adding acid to water vs water to acid, I’ll keep that in mind next time I’m working with any caustic substance. Fortunately I’m already geared up with eye protection/gloves/ventilation for etching circuit boards, I’m already safer than I need to be with that process so I don’t plan on taking any unnecessary risks with a more dangerous process, I’m a fan of my eyes and fingers so I don’t plan on burning them off anytime soon! :slightly_smiling:


#7

Hopefully HCL will have a little bit more of a kick to it than salsa :smile:


#8

I would strongly urge you to avoid straight HCl as an etchant. When strong enough to etch well it has the bad habit of rusting EVERY piece of ferrous metal within range.
Ferric Chloride is very useful for a variety of materials, is much safer to deal with, and produces a significantly lower volume of fumes.

For materials that don’t respond well to Ferric Chloride, I would always choose dilute Nitric acid over Hydrochloric. There are also other good solutions (pun intended) you might try. For copper based alloys (copper, brass, bronze) you might look into Copper Chloride in Aqueous Hydrochloric Acid, which works well and uses HCL in a much diluted form.

For deep etching, the commercial systems use air bubblers or even pumped etchant to try and keep things going straight. Your ability to replicate these systems is going to be based upon your ingenuity and willingness to assume risk. :slightly_smiling:


#9

Don’t worry, I wasn’t planning on, it was just a throwaway remark about it having a bit more bite than salsa :smiley:

That said, it’s a remark I’m glad I made, your replies are incredibly informative, very useful stuff!


#10

Then you’ve never had my salsa!