Etching Into 18k Gold

[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.

Gold_Lion_w.jpg

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.