Etching Into 18k Gold

[Tim Bateson]

Now I have always avoided jewelry engraving. A local Diamond Cutting & Jewelry design shop has convinced me to try to etch an image into a piece of 3x2 inch of solid 18k gold plate.

Disclaimers aside, has anyone done this and have any hints?

Attached is a sample of the image I cut into aluminum.
319961

[Gary Hair]

of solid 18k gold plate.

Not sure it would work either way, but there would be a difference between solid and plate. Plate would reveal the base metal and solid wouldn't.

[Mark Sipes]

According to the clip on YouTube https://www.youtube.com/watch?v=OkGX8JAy-d4 A ceramic based material is applied... I assume it it Cermark does not tell the wattage but looks as good a stainless.. Won't the Fiber mark gold https://www.youtube.com/watch?v=hqqlyFSkyZo

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[Tim Bateson]

I plan to use the Fiber to etch into the gold. I'm sure I can, but worried the gold may warp as I etch it.

[Scott Shepherd]

Gold is also highly reflective. I'd be concerned about backscatter frying my tube.

[Mark Sipes]

As we tell the "new to engraving" several passes on low power is better than 100 power on your first attempt of a new material... spray the surface with a light coat of powder. Pam with baking flour comes to mind...




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[Mark Sipes]

Gold is also highly reflective. I'd be concerned about backscatter frying my tube.


Not to be a smart a** but rather to understand. How does the reflective surface cause the tube to be in jeopardy. Does the reflective beam traveling back through the lense and mirrors, overpower the beam leaving the tube and then frying the optics at the other end. I understand the lense is in a direct path of the scatter, just don't understand the tube part.

[Scott Shepherd]

Mark, I've been told that when it does happen, and I'm probably saying this wrong, it combines with the existing beam, heading backwards, and it can fry the tube. Even if it doesn't make it that far, backscatter can be bad for many things. I'm not suggesting you can't engrave gold, just that as a new user of the fiber, that might be a good question to ask the people that make your machine before throwing it in there and giving it a whirl. The risk might be zero, but in industrial lasers, shiny things like brass, aluminum, and copper were always very dangerous to deal with and those systems had some high dollar, serious protection to keep things like that from happening.

Just food for thought before someone fries a brand new $60,000 laser.

[Gary Hair]

spray the surface with a light coat of powder. Pam with baking flour comes to mind...

Please elaborate Mark, I've never heard of this before.

[Mark Sipes]

Well I just figured to cut down on the reflective surface a thin coating of dust would reduce the "scatter" so talked about as a damaging force to the tube and optics. When I am laying out acrylic awards I spray the surface so I can better see the red dot in placement of text and alignment. Clean up is a snap.

[Michael Hunter]

I thought the point of fiber was that the beam energy is absorbed by metal, rather than being reflected?

I can understand Tim's worry though - anything gold is by definition an expensive item and therefore potentially costly if anything goes wrong.

[Dan Hintz]

You will be very unlikely to make a dent/scratch in gold... even at the 1um wavelength of "fiber", gold is just too reflective. You really need something about half of the wavelength to get sufficient power into it.

[Scott Shepherd]

I thought the point of fiber was that the beam energy is absorbed by metal, rather than being reflected?



You'll still have the possibility of something highly reflective going back into the lens. The difference is that it's now a focused fiber beam going backwards into the system. Not something you'd want to happen on a brand new, high dollar machine.

[Michael Hunter]

You'll still have the possibility of something highly reflective going back into the lens.

If the metal absorbs the beam power, then it isn't reflected back into the optics.

But now Dan says that gold *is* reflective at fiber wavelengths.


I'm confused here - Trotec specifically mention gold in the list of materials that their fiber laser will engrave and Epilog claim their fibre will mark "almost any metal".
So which metals are truly suitable for fiber engraving?

[Dan Hintz]

If the metal absorbs the beam power, then it isn't reflected back into the optics.

But now Dan says that gold *is* reflective at fiber wavelengths.


To be clear... gold is nearly 100% reflective at 1um wavelengths (most of what people have). You don't get into real absorption amounts until you're below about 600nm. Gold has a nice little absorption peak around the 530-540nm mark, so a green laser at 532nm is often the best choice. The problem is, green lasers aren't nearly as powerful as your typical 1um fiber (dollar for dollar), but the absorption is so strong there you don't need to be that powerful.

I can't say I've ever tried gold with a 1um fiber... never any call for it. But feel free to try and let me know how slow you have to go before you start to make a dent.

[Chris DeGerolamo]

*patiently waiting for the actual engraving while chanting 'do it, do it, do it'*

[Michael Hunter]

But feel free to try and let me know how slow you have to go before you start to make a dent.

I'd love to try it, but I don't have a fiber.
I do lots of anodised aluminium with my CO2 and some stainless with cermark or plaster. To be able to mark other metals - particularly precious metals - (without resorting to cermark or similar) would be very useful, but I'm unlikely to invest in a fiber if there are a whole load of metals that it WON'T work with.

Whilst I'm aware that the machine manufacturers claim as wide a range of materials as possible, I'm puzzled that Trotec claim gold if it is really very difficult and potentially damaging to the machine.

[Dan Hintz]

Whilst I'm aware that the machine manufacturers claim as wide a range of materials as possible, I'm puzzled that Trotec claim gold if it is really very difficult and potentially damaging to the machine.

I just looked up info on their fibers... they're Q-switched, which means they could be pulsed with very high powers. How high isn't listed, but with the extremely low absorption value for gold, you really need high power to remove/mark material (similar to a piece of 1/8" stainless steel laughing at a 100W CO2 laser trying to cut it, but a 1kW CO2 laser would blast right through it). If Trotec (or anyone else, for that matter) can pulse with enough peak power, then yes, it could likely mark gold. If they claim they can mark it, then bets are they have a decent amount of peak power coming from their setup. A 30-second search on Google for Epilog and ULS did not turn up anything about using Q-switched fibers, so more searching would be necessary to determine if they can, as well.

[Tim Bateson]

OK, Here is the result. I wasn't much worried about it being reflective even though it was like a mirror, as the lens will focus for a given distance, the reflected beam would no longer be in focus upon reaching back to the lens.

Now, they've given me a blank check (metaphorically speaking) for this piece, I have to decide what this work is worth. I know the Jeweler will be shaping this gold plate around the outline of the Lion, applying it to a big gold bracelet, then bending to fit the client's wrist - This image was a special request of his client.

319990

A lot of gold dust left on the laser bed, any hints for collecting it? This plate was so reflective it was hard to get a good shot of it.

[Matt Geraci]

Tim-
Great work! Bold engraving!! To the victor go the spoils!!
I tried to find some answers on this topic... dug a little deep...

"...The reflectivity of a given material will depend on the frequency of the lightsource through the dispersion relation of its index of refraction. For instance in thecase of normal incidence, values for reflectivity of metals in the near UV and visiblespectral range are typically between 0.4 and 0.95, and between 0.9 and 0.99 for theIR [7]. In addition, the reflectivity of a surface will depend on the temperature of thematerial through changes in the permittivity, band structure, plasma oscillations, ormaterial phase [19]. For instance, upon melting, the reflectivity of silicon increasesby a factor of about 2 [20], while that of a metal such as Ni changes by only a fewpercent [21]. In the case of small scale or structured materials, additional optical resonancesare possible, such as surface and bulk plasmons and polaritons, which canlead to enhanced absorption or reflection due to the details of the photon–electroninteractions [22].Once inside the material, absorption causes the intensity of the light to decay withdepth at a rate determined by the material’s absorption coefficient ˛. In general, ˛ isa function of wavelength and temperature, but for constant ˛, intensity I decaysexponentially with depth z according to the Beer–Lambert law,..."

http://www.princeton.edu/~spikelab/papers/book02.pdf

PS- My fiber is built! Shakedown and testing in progress... should ship within a week or so!

[Scott Shepherd]

I wasn't much worried about it being reflective even though it was like a mirror, as the lens will focus for a given distance, the reflected beam would no longer be in focus upon reaching back to the lens.

Yeah, that's not how it works, it 100% can damage the mirrors from a reflection. Looks like it worked out alright which is great, but don't talk yourself into a false sense of security that the beam is too out of focus to reflect back into the lens because that's not true.

[Mike Null]

Tim

Nice job. Thanks for sharing that photo and info.

[matthew knott]

Gold is not really difficult to laser with a fiber laser, a short lens helps , 100mm would be a good choice, it is very possible to damage the optics in the machine, recently someone here with a galvo machine sent me photos of damaged galvo mirrors that have been caused by back reflection. Pretty much all fibre laser used for engraving are q switched , all with similar specs , normally made by SPI , IPG or raycus and a few other company's . Intrestingly copper is much harder to engrave and an old fashioned q switched yag is a better option as it has much higher peak powers.

[Matt Geraci]

What is the incidence of damage from back reflection on galvos and any ways or tips to avoid it? I've been doing a lot of reading on the technicalities of fibers and industry studies. The best quote I've heard was something along the lines of engraving with fibers is still much of an artistically driven "black art"...! There are a lot of people doing some great work out there, but still a lot to learn and each person's use is different.
Mine should arrive within the month!


Gold is not really difficult to laser with a fiber laser, a short lens helps , 100mm would be a good choice, it is very possible to damage the optics in the machine, recently someone here with a galvo machine sent me photos of damaged galvo mirrors that have been caused by back reflection. Pretty much all fibre laser used for engraving are q switched , all with similar specs , normally made by SPI , IPG or raycus and a few other company's . Intrestingly copper is much harder to engrave and an old fashioned q switched yag is a better option as it has much higher peak powers.

[Tim Bateson]

... The best quote I've heard was something along the lines of engraving with fibers is still much of an artistically driven "black art"...! There are a lot of people doing some great work out there, but still a lot to learn and each person's use is different...

Settings for the Fiber are nearly impossible to find, as compared to a CO2. You will find a lot of incomplete settings such as Speed/Power/Frequency. I say these are incomplete as they don't account for DPI at all & it does make a difference (on my machine). Also these settings are very vague as a Fiber can make many types of marks and or etchings, depending on modifying Speed/Power/Frequency/DPI/Focus (ALL 5 settings do matter). That's a lot of variables to pick from, especially when you have nothing but the client's piece to test with. I have asked a few members on this forum for assistance, but no response. Either they are as lost as I am or choose not to share the knowledge.

I have a whole month and half with mine and have a zillion notes so far. Some good & some not so much. I still hate Marking Aluminum as the fiber is of little help, same with Pewter and Copper. Note, bad luck with all of these, but refining settings without test pieces will take a long time if ever to find good settings. Cutting into material hasn't been as hard to figure out. That part of my business is now booming!

[Gary Hair]

I say these are incomplete as they don't account for DPI at all & it does make a difference (on my machine). Also these settings are very vague as a Fiber can make many types of marks and or etchings, depending on modifying Speed/Power/Frequency/DPI/Focus (ALL 5 settings do matter).

If you throw in the gantry vs galvo then you get another set of variables - hatch angle and multiple passes with different hatch angles on the same job. My guess is that you don't find people willing to give up their settings because either they haven't figured it out yet or their machine and yours are just different enough that the settings would be useless. My galvo, for example, would have nothing in common with your gantry machine so what works well for me would not be possible for you to replicate with the options on your machine and vice versa.