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View Full Version : Weird Gradient Effect When Engraving Anodized Aluminum - Should Not Be There



Tracey Bakewell
01-27-2012, 4:51 PM
I just did a sample run for a new customer (ack!) For his pre-production video of this new product they're selling. Anyway, this could be a very good thing for me. I did a test, this did not happen, I did the real thing, the logo is larger about 5" square. Lost of engraving off the surface area. If you look in the picture, you can see where there are weird gradient lines forming about an 1" into the job. He was fine with it for now, but said when we go into production, we need to get that figured out. I don't have any product to test on until he brings me the real thing and he'll have one then for me to work with, might be weeks away.

Anybody know what this effect or problem is called?

I have a Universal Laser 50 Watt, and here were my settings for anodized aluminum:
power: 100%
speed: 25%
ppi: 500
Image Denisity: max (6) or 1000 whatever works for you

Jerry Hewett
01-27-2012, 5:03 PM
What is the file type your using?

Mark Sipes
01-27-2012, 5:06 PM
I would have run a second pass on the item at 600 dpi to make sure it was a laser problem and not a product material problem.

500 PPI is pulses per inch not DPI dots per inch


100 at 25% with a 50W should have taken the coating off...

Tracey Bakewell
01-27-2012, 5:07 PM
What is the file type your using?

CorelDraw x4, very simple all vector artwork.

Tracey Bakewell
01-27-2012, 5:10 PM
...and not a product material problem....

I was concerned about that. I asked, what did it look like before it was anodized so he brought one it that was before being anodized. Unfortunately, I think they treat the metal with something prior to being anodized so it really didn't do me any good to see the beginning product. I will definitely try that second pass.

Scott Shepherd
01-27-2012, 6:16 PM
Sounds like way too much power to me. Try the materials database settings for anodized aluminum. They are close and do a good job. That just sounds like a heck of a lot of power to me. I'll check my settings when I get back in front of our Universal.

Scott Shepherd
01-27-2012, 6:18 PM
Too slow too, and try image density of 5.

Dan Hintz
01-27-2012, 7:34 PM
Man, what is it with people cooking aluminum lately? On my 60W, my settings are 100S/20P/500ppi @ image density 5 (which is 500dpi). At your power, you're not just bleaching the dye, you're likely removing the anodized finish altogether.

That said, the ripple looks like a substrate defect, not a laser issue. See if you can view a few before they're anodized... mark them as a separate batch, let them be anodized, and then see if that pattern reappears.

Frank Corker
01-27-2012, 8:25 PM
I'm with Dan here, I can't figure out why people are using such high power to such low speeds, if anything they should be reversed to what you've done. I have a 45w and mine are 300dpi 100s/90p 400dpi 100/80, 600 100/70. With the newer manual the settings have been marked with even less power than those I've given. Tracey I'd also look at the file that you have used and change the engraved area to RGB instead of CYMK.
.....and Happy Birthday too!

Tim Bateson
01-27-2012, 10:35 PM
Just Yesterday, I spent an hour on the phone with a customer trying to explain that lasering - when done properly, should never remove anodization. A bleaching is all you really need and that as stated already doesn't require much power. Anodization can fill fine voids in the surface & if you removed a layer of it.... voids reappear. Probably polish scratches prior to being anodized.
At 35w, I always use 100% speed and 35-50% power depending on photo or text/graphic.

Rodne Gold
01-28-2012, 2:26 AM
I would do that engraving as a 90% greyscale and at something like 2-300 dpi - will go 2x as fast and give the same effect or better and stop moire and other artefacts. you can defocus a teeny bit if you go to the lower end of the dpi.

Scott Shepherd
01-28-2012, 9:21 AM
I just checked a job I run repeatedly that's black anodized. It was 100% speed, 30% power, Image Density of 5, on a 45W laser. Leaves a nice white mark.

Martin Boekers
01-28-2012, 6:24 PM
Check to make sure that Corel doesn't have any weird ICC profiles or that your not running in
CMYK I have had some strange things happen when that happens.

On the power and settings, you guys are right, on sheet stock I care it's quick and easy, but
some manufactured pieces like the JDS water bottles took a couple REALLY heavy passes
to get it done, you could feel where it lasered through. As mentioned previously I finally
tried the standard setting and cleaned it with a magic sponge and windex. So there is something
happening with some of these processes out there.

Rodne, don't know if you had a chance while in China to check out the andozing processes and
see how there may be variences that affect the power and speed to get it done.

Rodne Gold
01-28-2012, 8:39 PM
Colour anodising isn't a precise process, most plants use their own variation of dyes , thicknesses of anodic layers vary and sealants vary too.. that's locally

I have no idea of how they do it in China , suffice it to say that my perspex and engraving laminate supplier sent us some sample brushed anodised sheet pieces and they were up there or exceeded the best I have seen , visually. I didnt try laser them.

Dan Hintz
01-29-2012, 9:15 AM
As Rodney, said, it's not precise... though the better anodizers have it down to a science (art form?). The best anodizers have computer-controlled, voltage-controlled power rigs, they are always checking their solutions for proper content, etc.

Mike Mackenzie
01-30-2012, 3:16 PM
+1 on the power 20-30% max should be all that is necessary also image density 5. I would check with your customer and ask him what type of anodizing process was used.

I know that type 3 anodizing is a real bear to mark correctly all others should be no problem. I believe that image density 6 could cause this pattern.

Also you can mask it by using the texture function in the advanced tab.

Neal Schlee
01-30-2012, 7:41 PM
If you look in the picture, you can see where there are weird gradient lines forming about an 1" into the job.
Anybody know what this effect or problem is called?


Looks like worn head bearings and/or a worn anodized cross rail. Try running a pc. of clear acrylic and see if you get the same effect in the bottom of the cut.
If your rail is worn on one side try lasering at a different area.

Neal
ULS X-2 660 120 watt