laser engraving on anodized aluminum

Hello,

I am new to laser etching/engraving. I work at a machine shop that has a 40W laser engraver. I have been trying to get a nice crisp logo (25mm x 2mm) on black anodized 6061 and 7075. I can get a pretty good looking logo, but it appears more blue/grey than white. Other parts that I see the laser etching is really white.

I've been playing with the dpi setting, speed, and the power settings. More power seem to turn the etching brown. Too little power and the logo barely appears. Speed doesn't seem to affect it at all.

Any suggestions?

Thanks,

Chris

This may be an obvious question, but have you tried adjusting the focus of the laser instead of the power?
We have a very similair setup and have run into this issue in the past. That is how we fixed it.

Yes, I have. It seems like the power and the focus are linked. I've been trying to keep one variable constant and changing other to see if I can work this out.

I currently have my lens about 54mm from top of part. This seems to get me the smallest laser point. If I bring the lens closer, say to 52mm, the etching comes out blurry at any power. If I leave the lens at 54mm, more power makes etching brown and blurry.

I'm stumped. Are there more variables I can adjust?

First, make sure it is regular black and not 'hard' anodized as that is almost impossible to remove cleanly.

Second, use 2-passes to get a nice clean result. The initial pass will remove 90% and leave it grey but the follow up will clean it up nicely.

Zax.

Quote:

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Originally Posted by zax15uk

First, make sure it is regular black and not 'hard' anodized as that is almost impossible to remove cleanly.

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I was just about to ask this as well. I was thinking that maybe the problem lies with the part rather than the machine.

pretty sure these parts are not hard ano.

I'll try two passes

does anyone have any general settings to use for engraving on anodized aluminum? low power high speed? 500 dpi?

thanks

I usually get good results with 2-passes of 10W @ 12cm/s using 250dpi.

(this is on dog tags which have a pretty thin anodized coating)

Zax.

i'll send a photo in a few minutes. I am engraving over a part that has been lasered by another company. I cannon replicate the clarity or the colour.

this is a part that has 1 laser etched logo that a supplier did for us. It is the logo that is the whitest and most crisp. all the other engraving was done by me.

can anyone tell me what I'm doing wrong?

many thanks if you can!

Chris...

A few questions for you.....

What machine are you using? My machine has an Image density as well as PPI level. I usually lower the density for fonts depending on the material.

You said you are new to laser engraving...have you checked the rudimentary first?

Cleanliness and condition of lenses and mirrors? There are 4 or 5 depending on the machine, in the engraving cabinet.

Also, have you checked the beam alignment?

I haven't etched much Anno Alum, but quite a bit of Anno Pot metal and chrome. The color coming through the etching is usually the substrate. I can't remember if any of the alum. I have engraved ever had a white color to the finish product.

In my opinion...it,looks like the finished engraving your source supplied was color filled. Rub and Buff works wonders!

Phil

I second that... it looks like it's color filled to me. It's just too white. Can you use something sharp and scratch inside the engraving to see if there is a white coating?

Thanks for the suggestions.

Late Friday afternoon I tried engraving in a different spot in the machine's travel and found that the mirror positioning is off: the laser didn't make it to the last mirror/lens. I'm going to have to adjust.

I'm not sure what kind of machine it is, no label or manufacturer on it.... seems like a Chinese machine. The software I'm using is MoshiDraw.

Can you tell me about the colour fill? How would I do that? I tired scraping the sample laser etching and it does seem to come off easier than what I etched... so maybe it is filled... I like the look and I'd like to replicate it.

Glad you're making headway. Yes, the mirrors need to be adjusted right on for best results. You do have a Chinese machine if you are using MoshiDraw. Zax can help you out with questions about it.

You can color fill a couple of different ways. You can mask the area with masking tape before you engrave it, engrave through the tape, then airbrush paint into it. Or like Red Earth said, you can use a stuff called Rub-N-Buff that is a colored wax (I think) that you rub into the engraving then wipe/buff off the excess. I've never used it so I'll let someone with knowledge of the product fill you in. I'm wondering if that stuff might stick to the original finish too though.

Skip

Rub & Buff is an oil based paint stick. just rub on and remove the excess with a cloth. You can also dampen it with WD40.

It's not permanent.... So.... using the mask method and a rattle can or air brush would suit your purpose better.

On your part... using a small width of masking tape will suffice. on larger applications I use transfer tape for transferring vinyl.

Phil

Car touch-up paint works well for small areas too. It is easy to apply and the finish is extremely durable.

Zax.

I have a part that I sell, that is hard anodized and lasermarked. These parts look very similar to your sample. I think the key is the type of laser. Hard anodize must be lased with an Nd:YAG laser, not a CO2. I have not seen the type of laser mentioned in this thread, by my guess is it is a CO2.

Here is a link to one sample:

http://images41.fotki.com/v1252/phot...SCN9412-vi.jpg

The mark is pretty much "pure white" and VERY durable.

Note, you will NOT get this type of mark on regular black anodize, which is really just clear anodize dyed black. To check if your parts are regular or hard anodize, try to scratch them with a key. Regular anodize will scratch off, down to the aluminum, very easily. Hard anodize will be difficult to scratch, and may chip off if you really go at it.