Technical challenges of building DIY laser rust removal gun.

[Psi]

This subject is likely to invoke dire warnings about the risks of eye damage and the like.
But please refrain from posting them, i have worked with lasers before

Has anyone looked into building a 'small' DIY laser rust removal gun, or seen others attempt it?

The professional units look to run between 20W and 1000W of pulsed and scanned 1064nm.
Costing around $80k to $400k

Some initial research shows you can buy 10W 1064nm laser diodes from china for $300 or so.
And 300W 1064nm water cooled Q-switched for ~$1000
(sorry, i'm not posting links to super powerful laser diodes. If you cant find it yourself you definitely shouldn't be buying it)

Does anyone know the actual reasons why laser rust removal guns are so expensive?
- Is it just a minefield of regulatory hoops to jump though pushing up the price
- Are they just so novel and work so well they can dictate whatever price they want
- Maybe they own patent on the tech.
etc.
Or is there a part inside that actually costs a significant percentage of the $80k to $400k price?
Maybe it needs a special kind of laser? Q-switched etc. and simply pulsing a diode laser wont work?

Obviously any DIY unit would be more in the 10-50W range rather than 1000W, but even 10W would be useful.

[Psi]

Looks like the issue maybe getting a q-switched laser with short enough pulse width to burn off only the rust
All the lasers i'm finding are 400ms or so and i think it needs to be down in the nanosecond range.

[Weston]

All Q switched lasers are going to produce pulses in the ns region, it is a population inversion thing and thats how long it takes the dynamics to play out. If you are seeing values in the ms range I assume the listing is wrong or it is not a Q switched laser.

Please PM me the link to the Q switched laser if you don't want to post. I am curious and that sounds too cheap to be true.

Lasers have gotten a lot cheaper but have historically been really expensive. A rust removal system probably has a set of galvos with dielectric mirrors and a f-theta lens, nothing that would be $10k++.  Given the high peak powers needed to remove material like this I am dubious you could use normal diode laser. Once you have a Q switched laser with enough pulse energy you should be able to remove rust, it just becomes a matter of how long you can wait.

[SilverSolder]

A gallon of phosphoric acid is cheaper and gives longer lasting results!

[coppercone2]

this is useful for an antique furniture dealer or something

[Zip]

In turn the laser will get rusty

[CM800]

Some initial research shows you can buy 10W 1064nm laser diodes from china for $300 or so.
And 300W 1064nm water cooled Q-switched for ~$1000

I will eat my hat if you can legitimately purchase a working 300W Q-switched YAG or Fibre laser for ~$1000
I've had a quote from a chinese company for just a pumping diode (300W, 915nm) at $3k
(You would need 1.5 to 2 of these, as the efficiency for pumping is not very good)

The YAG / fibre optics are even more expensive, at 300W you will need water cooled mirrors, a very well designed cavity etc... Everything becomes hell working with those power levels, as using the wrong optics, or slight imperfections / dirt will ablate and ruin the components...

Looking around, a Q-switched 100W 1064nm will set you back ~$14k from a chinese, less then reputable company. You could expect significantly more for a western brand I imagine (though admittedly I haven't got quotes)

The price goes up exponentially with power... I truely wish you could by a 300W QSW 1064nm laser at $1000, the world would be a better place... (And my wallet would be much emptier, there's a lot of projects I'd love to work on, but the cost is too prohibitive.) but not yet!

[Psi]

Lots off good points.

Thanks guys

[Marco]

The modern way to cobble together a pulse laser in university labs seems to be all fiber, you can get double clad fiber COTS. It's not cheap, but cheaper than trying to negotiate for a one off big crystal. Personally I like the concept of amplifiers over Q-switching ... it avoids having to switch high powers. If you can get a PhD with laser experience to put it together for you, the components are probably not that expensive. The PhD's time moreso.

[StuartA]

I'm not sure if it is of interest here, but I recall that some time ago, people were investigating the use of citric acid solution together with high intensity lights for de-rusting. Citric acid is a very weak acid, but a good chelating agent and can be used on its own to remove rust.
Exernal lighting is obviously intended to add energy to the system and speed things up, but I don't recall the exact nature of the lights or the proposed mechanism of the process.

[james_s]

Lasers are certainly cool, but a gallon of Evaporust is only about $25, it's reusable for quite a while and does a good job. Electrolysis is simple and cheap for larger items.

[duak]

I didn't realize these things took rust off too.  I saw a video where one unit cleaned a cylinder head up pronto.

I worked with laser devices that delivered over 20 W of near IR at the film plane to expose printing plates. If you looked at the media while it was working you'd see a white spot about 2 mm wide.  Depending on the media type, there could be stuff blown off in little flakes or ribbons.  I think I have a bar laser with one bad facet somewhere.  I know that kind of laser has enough snot to burn holes thru fabric if properly focussed.

FWIW, here's what I think about the costs:

I'd bet there's at least $10K of parts for a low power unit.  I see there are at least a dozen companies making these things.  I don't know how big the market is or how it's divided up.  Some companies seem quite small.  I wonder if the light source is an off the shelf part or custom.

I shepherded two products through the US regulatory agency for laser products (CDRH) about 20 years ago.  It wasn't all that difficult - nowhere as difficult as getting approval for medical devices.  At that time, I did some tests and submitted some reports and that was that.  I didn't need to send a sample device for testing.  It's probably tightened up since then but since this device is Class 4 and inherently hazardous I'd expect that training in proper usage is a part of the cost.  I hope they've figured out some way to prevent the user from accidently exfoliating someone.  If not, maybe they've set aside money for good lawyers.

My experience with lasers and optics handling real power is that they degrade or even die for non-obvious reasons.  I expect that dropping the head on the floor will not do the galvanometer any good.  Any contamination on an internal optical surface with a high power density is bad news.  Dust gets pushed there by the laser beam so we had clean rooms and protocols for assembly and integration of our products.

After seeing how workers use tools in a machine shop, I'd say that a laser cleaning system should be designed to take abuse.  To make something reliable for an industrial workplace takes some real engineering, testing and money.  I remember a talk by one of my colleagues who used to work for Leica optical systems.  He designed an eyepiece for an optical sight for use in a tank to aim the gun.  He had a prototype handy, so to show how tough it was, he smashed it down on the edge of a table.  The whole assembly had to be able to handle being stepped on by the gunner as they got in or out their seat.