PDA

View Full Version : Black marking on aluminium without cer/thermark



Arjen Abbestee
03-12-2014, 12:09 PM
I'm sure this has been asked before, but my search returned no answer... What kind of laser (in terms of wavelength and power) do I need to make black (or at least very dark) markings on clear anodized aluminium like the back of an iPad? I have a CO2 laser that suits my purposes fine but the question 'can you make black markings on my ....' comes up quite often...

tnx, Arjen

matthew knott
03-12-2014, 1:25 PM
Fiber laser or YAG is what you need, so around 1000nm, it will get you a very dark grey that most would be happy to call black. Much harder to get black on plain aluminium but clear anodised is ok.

Arjen Abbestee
03-12-2014, 3:48 PM
Thanks, I figured it had to be around 1000nm, since yag/fiber and co2 are the most 'common' lasers used. If time is of no importance, what would be the minimum wattage to make dark mark (not the Harry Potter kind) on anodised aluminium?

matthew knott
03-12-2014, 3:52 PM
10 watt would be fine for muggles like us !!

Arjen Abbestee
03-12-2014, 4:19 PM
But I still feel like a wizard when I cut thing on my machine!
Now I'm starting to wonder if it is at all possible to 'convert' my machine to a YAG. I know Trotec has a machine that does both, but I assume you cannot use the same optics for both CO2 an YAG due to the very different wavelengths. But if I read it right a yag laser module plus power supply can be had for less than $1000,-. But I'm sure there is more involved than just replacing the CO2 tube with a yag module...

matthew knott
03-12-2014, 4:29 PM
dont think you will get a pulsed yag laser for $1000 !! A fiber laser source is about $5k, then a whole load of work, you can use the same optics in both 'IF' you have the right optics, glass type (normally used for yag) is a no-no as the co2 will destroy them. In theory in can all be done but its fair from easy and you would need to know exactly what your doing plus all the safety implications to think off ! My advise don't try it Arjen

Arjen Abbestee
03-12-2014, 4:35 PM
I may feel like a wizard but I know very well I am not one. So I won't try anything before I know everything there is to know about this stuff and as you may have guessed I have a long way to go...
I saw this page (don't know if posting links is allowed here): http://www.aliexpress.com/store/group/YAG-Laser-Mark-Machine-Parts/926078_252099148.html
Maybe this stuff in not at all usable, like I said, still a lot to learn but having so much fun doing it!

matthew knott
03-12-2014, 5:06 PM
thats a good price for a diode side pumper head, i remember paying ££££'s for them. you still need to add a diode PSU, a q switch, a q switch driver, a water cooling system (+/- 0.1 deg), front and rear mirrors, beam expander, a load of machined metal work, wire, some electronics and you off and running, think about another 4k of parts to start lasering !!

Arjen Abbestee
03-12-2014, 5:25 PM
So this will be something to consider when I look out the window and see a long queue of people all waiting to have their iPad engraved in black. Not anytime soon I guess, but one can dream...
It would be nice though to have a machine that can be converted from co2 to yag when needed. When the optics are the same you'd 'only' have to replace the tube (and connect the right supply and driver etc.) and you're good to go. Oh well, maybe some day.

matthew knott
03-12-2014, 5:43 PM
Easier, better and probably cheaper just to get yourself a new fiber laser that's ready to go, then you have both that you can use at the same time! just stings the wallet a bit at first!!!

Arjen Abbestee
03-13-2014, 6:15 PM
Ah, now you're being practical. Where's the fun in that?

Chuck Stone
03-13-2014, 9:37 PM
can you overpower (remove) the anodized layer and color fill?

Arjen Abbestee
03-14-2014, 3:42 AM
My clients mostly come in with iPads/phones/laptops they want engraved. That's why I don't want to use anything wet like cermark or paint...

Has anybody tried a 445nm laser on anodised aluminium?

Jeff Woodcock
03-15-2014, 7:07 PM
Has anybody tried a 445nm laser on anodised aluminium?

Yes, I have used a 445nm on anodized aluminum. I had to go real slow with 4.5W of power.

Arjen Abbestee
03-16-2014, 4:37 AM
That does not look bad at all (and I'm talking about the engraving, though the same goes for the girl in the picture :D).
Did you build your laser engraver yourself?

Jeff Woodcock
03-16-2014, 7:09 AM
Thanks Arjen,

We built and installed the 445nm LD engraving systems on two of our CNC routers. Both are 4 axis machines.

Arjen Abbestee
03-16-2014, 8:33 AM
4.5 Watt seems like a lot for a Laser Diode. Where did you get it and how much did you spend?

Jeff Woodcock
03-16-2014, 9:19 AM
We are using two 2.25W 9mm Nichia LD's focused to the same intersecting focal point and it's mounted on our servo CNC router. The Nichia 9mm LD came from DTR on eBay for $99 each already pressed into a copper module and included a 3 element glass lens. The analog modulation driver is a Flexmod P3 and is around $35. On our first build, the mini CNC router is only a 1W and it uses a Flexmod P3 also.

Here is a video of our dual LD engraver shading a 3D spindle engraving. We were only using 2/5 of the full output power on this project.


https://www.youtube.com/watch?v=rUIrS3Ot1I4

Arjen Abbestee
03-16-2014, 11:57 AM
Good idea to combine two lasers in the same focal point. Should have thought of that myself. The price of laser diodes seems to rise exponentially with power, and since I don't want to spend a fortune on an experiment this is just what I was looking for. Now that I know that 445nm will blacken aluminium I guess other wavelengths between 445 and 1064 (fiber/yag) nm will also work. Lots of possibilities to play with now!
Good video by the way. I love how the vertical axes is used to retain focus. Halfway through the video is a shot of a motor driving something. Is that a mechanical laser-power-control?

Jeff Woodcock
03-16-2014, 2:14 PM
Actually Arjen, the 445nm whitened the black anodizing with high power and at lower power it stays black. The servo motor down below (4th axis) drives a US Digital MA3 magnetic shaft encoder. It gives us 0-5 varied analog voltage output to the Flexmod P3 LD driver based on a 0-360 degree rotation to vary the power. We power it with the 5v from the USB port on my PC.

This spindle/laser process takes two same size images, one is a greyscale height map image for the 3D spindle engraving and the second is a color or 8bit greyscale image for the shading. We use Mach3 for the controller program which is gcode driven and it's an open source option so we don't have the restraints of a proprietary program. We generate two gcode files with Picengrave image to Gcode program we use and then combine the two files into one. X,Y & Z from the height map image file and A from the other image file for varying the laser diodes power. It gives us X,Y,Z & A movements in one file so the LD's focal point follows the contours of the spindle engraving. The gcode we generate is 40,000 PPSI (Positions Per Square Inch).

Since the MA3 encoder has 10bit resolution, even at a half power setting, there are 512 incremental voltage changes to the analog modulation input on the LD driver with a A.0000 to A-.0256" full depth setting (8bit). To set the max power for the LD, we just change the Steps Per. in Motor Tuning in Mach3 for the A axis servo motor.

Our servo CNC router's spindle mount excepts both the spindle and Laser engraver so it eliminates alignment issues like when using two different machines.

Arjen Abbestee
03-16-2014, 5:47 PM
I'm impressed! Very nice combination of techniques.
I'm shopping for a 2W laser now. I'll attach it to the X carriage of my CO2 laser so I will use all the electronics and mechanics from that machine. That means the laser + mount has to be as lightweight as possible, it's not a heavy CNC milling machine capable of carrying 'lots' of extra weight.
Then it's a matter of finding the right speed/power combination. This will only be for black marking of anodised aluminium (read iPads/phones etc.). For all other purposes the CO2 tube does everything I need.

Jeff Woodcock
03-16-2014, 6:08 PM
Thanks Arjen,

It has been allot of fun with these builds. I like figuring out multitasking ways to use my CNC router. I have even thought about a 3D printer attachment to go on it in the future. I would post some links to the components you may need, but that is not allowed on this forum. Just search on the net based on my description. I would also recommend a Lasorb for ESD protection for the LD.

Arjen Abbestee
03-16-2014, 6:25 PM
You could pm me, but there are so many sellers for this kind of stuff I won't have a problem finding it.
Thanks for all the info.

Dan Hintz
03-17-2014, 8:00 AM
I'm impressed! Very nice combination of techniques.
I'm shopping for a 2W laser now. I'll attach it to the X carriage of my CO2 laser so I will use all the electronics and mechanics from that machine. That means the laser + mount has to be as lightweight as possible, it's not a heavy CNC milling machine capable of carrying 'lots' of extra weight.
Then it's a matter of finding the right speed/power combination. This will only be for black marking of anodised aluminium (read iPads/phones etc.). For all other purposes the CO2 tube does everything I need.

Why would you do this?

You still seem to be under the impression the laser Jeff mentions marks bare aluminum. It does not, it only bleaches the black anodizing already on it, just like the CO2 laser you already own.

Strapping another laser to your CO2 carriage would be like tying a Ferrari on top of a Yugo because the Yugo has wheels.

Arjen Abbestee
03-17-2014, 8:39 AM
Good catch Dan, thanks! Yes, I was under the impression that the 445nm laser leaves a black mark on clear anodized aliminium. Now I see that in the image Jeff posted it is a black anodized sheet where the image is lasered by removing the black. Bummer.
So I'm back to where I started. The only way to get black marking on clear anodized aluminium is to use a YAG laser. And that's too expensive for the amount of work I'd do with it...
Though I still don't get why only a 1064nm laser can leave a black (or at least very dark) mark on aluminium. I get why my CO2 with the 10 times longer wavelength won't work, but wouldn't a 808nm work as well?

Jeff Woodcock
03-17-2014, 9:59 AM
Strapping another laser to your CO2 carriage would be like tying a Ferrari on top of a Yugo because the Yugo has wheels.

Dan,

I do appreciate the compliment of your comparison of my 445nm LD build to a Ferrari, considering Ferrari's are mostly hand built too, but why do you have to insult Arjen with comparing his CO2 machine to a Yugo on wheels? Sometimes you just are not very nice in your comments, especially anywhere I have posted. The term a$$hole comes to mind.

Arjen, I did point out that the 445nm whitened the black anodize at higher power in post #20 and I thought you understood that.

Dan Hintz
03-17-2014, 10:02 AM
Good catch Dan, thanks! Yes, I was under the impression that the 445nm laser leaves a black mark on clear anodized aliminium. Now I see that in the image Jeff posted it is a black anodized sheet where the image is lasered by removing the black. Bummer.
So I'm back to where I started. The only way to get black marking on clear anodized aluminium is to use a YAG laser. And that's too expensive for the amount of work I'd do with it...
Though I still don't get why only a 1064nm laser can leave a black (or at least very dark) mark on aluminium. I get why my CO2 with the 10 times longer wavelength won't work, but wouldn't a 808nm work as well?

There is a peak in the absorption of aluminum at the mid-800's, but you'll want more than a couple of Watts to do much with it. Fiber/YAG is on the other side of that peak (and surprisingly far down) from visible, but it's usually in the 20W+ range for marking. Just as a CO2 can cut metal when you throw in enough power (kW levels), if you throw enough power at it in the near-visible, it will be absorbed.

Dan Hintz
03-17-2014, 10:05 AM
Dan,

I do appreciate the compliment of your comparison of my 445nm LD build to a Ferrari, considering Ferrari's are mostly hand built too, but why do you have to insult Arjen with comparing his CO2 machine to a Yugo on wheels? Sometimes you just are not very nice in your comments, especially anywhere I have posted. The term Stalking comes to mind.

Sorry, Jeff, but I was not comparing your machine to a Ferrari, nor was I comparing his to a Yugo. I was making an analogy... tacking a low-power laser of one wavelength (Yugo) underneath a high-powered laser of a perfectly usable wavelength (Ferrari) is adding an unnecessary step.

Scott Shepherd
03-17-2014, 10:08 AM
Dan,

I do appreciate the compliment of your comparison of my 445nm LD build to a Ferrari, considering Ferrari's are mostly hand built too, but why do you have to insult Arjen with comparing his CO2 machine to a Yugo on wheels?

I didn't read it like that at all Jeff. I didn't read it like he said your machine was a Ferrari either. I read it as saying that "You already have a C02 laser that will engrave anodized aluminum the Ferrari in the equation), why would you strap on a 2W laser (the yugo in the equation) to do something slower than you can already do with what you have must faster".

Seemed like a point well stated to me, and didn't mention you or even remotely talk about anything you did at all. I think you may have read his comments wrong.

Arjen Abbestee
03-17-2014, 10:10 AM
My mistake completely. Sometimes one reads what one wants to read. I assumed from the start that your 445nm laser marked black, because that was what I wanted to read. And as you know, assumption is the mother of all f••k-ups...
But I still enjoyed reading about your CNC-mill/laser-engraver.

Arjen Abbestee
03-17-2014, 10:23 AM
So you don't agree with Matthew's comment that 10 Watts should be enough? I suppose (newbie) that lower Wattage can be compensated by lower speed, but only to a certain point where the energy from the laser is simply not enough to have any effect on the metal even when the beam is standing still. Is that correct? I don't run a commercial shop, so speed is not my main concern.

Dan Hintz
03-17-2014, 10:43 AM
You can engrave with 10W, but your processing speed will be lower. I'm trying to be somewhat vague on specific values as they're not important, per se.