Laser Engraving Aluminum Surface Roughness

[John Kleiber]

Something I've lived with for the longest time when deep engraving aluminum is surface roughness.

While ablating aluminum anodized coating is breeze and leaves a smooth surface. The only way I have ever been able to alleviate roughness deep engraving is either abrasive blasting or burnishing afterwards.

Unfortunately, laser marking precoated parts leaves those options impractical.

Is this just a natural unavoidable reaction aluminum has when subjected to deep engraving?

[Kev Williams]

You're talking about the edge-slag on the surface, NOT the bottom of the actual cut, correct?

If so, I'd like to hear some suggestions myself

[John Kleiber]

You're talking about the edge-slag on the surface, NOT the bottom of the actual cut, correct?

If so, I'd like to hear some suggestions myself

Yes, edge slag. Bottom roughness is not a problem. But roughness to finished product drives me crazy.

[Gary Hair]

I use lower power, higher speed and higher frequency when I'm concerned about slag. For most of the lowers I engrave I use 300-500 speed, 40-60 power and 40-60 frequency - usually takes 50-100 passes but it's as clean as can be when done! Oh, the speed is in mm.

[John Kleiber]

I use lower power, higher speed and higher frequency when I'm concerned about slag. For most of the lowers I engrave I use 300-500 speed, 40-60 power and 40-60 frequency - usually takes 50-100 passes but it's as clean as can be when done! Oh, the speed is in mm.

Thanks Gary. I will run a test this morning using your settings side by side with mine from yesterday and report back.
Laser time is equally important. Hopefully I can make the mark in a similar time frame with better results.

[John Kleiber]

I use lower power, higher speed and higher frequency when I'm concerned about slag. For most of the lowers I engrave I use 300-500 speed, 40-60 power and 40-60 frequency - usually takes 50-100 passes but it's as clean as can be when done! Oh, the speed is in mm.

Gary,

I tried your settings, and while the settings worked somewhat, as a practical matter its a no go based on long laser times.
I'm looking for a quality deep mark, with a relatively smooth service, and high volume quick throughput per part.
I will keep experimenting.

-John

[Gary Hair]

The main factor is going to be time - how much time are you willing (able) to take and get the results you want. Faster engraving can only really be accomplished by using low speed along with high power and low frequency, unfortunately that leaves you with slag. You'll have to decide where the trade-off is between speed and results.

[John Kleiber]

The main factor is going to be time - how much time are you willing (able) to take and get the results you want. Faster engraving can only really be accomplished by using low speed along with high power and low frequency, unfortunately that leaves you with slag. You'll have to decide where the trade-off is between speed and results.

Time = $ and the customer has hundreds of industrial parts. I've informed the customer on what to expect based on the speed and they are ok with that.

In this case, industrial parts need to be more practical marked than pretty.

-John

[Scott Shepherd]

I'm not sure what rough edges you guys are getting. This is what I get in steel. I suspect that you are overpowering it far too much.

This was done today, so it's fresh in my mind.
IMG_4156.jpg

[John Kleiber]

I'm not sure what rough edges you guys are getting. This is what I get in steel. I suspect that you are overpowering it far too much.

This was done today, so it's fresh in my mind.
IMG_4156.jpg

Aluminum in the case regarding roughness. I've spent probably more time than practical messing with settings today to get a decent mark in an efficient time frame.
Nevertheless, the customer should be happy and part throughput speed should work well.

Aluminum is just funky. In order for it to atomize and remove efficiently by laser, it requires brute force.

[Scott Shepherd]

I engraved aluminum 5 minutes before that photo. 1 aluminum, 1 steel. Still don't see all the issues being described. Try changing your hatch spacing.

[Tim Bateson]

...
This was done today, so it's fresh in my mind.
IMG_4156.jpg

When I do steel like this I get a rust like color in the engraving.

[Kev Williams]

Like John, I'm in a hurry!

I have come up with a bit of a fix, doesn't eliminate the slag but it helps---

What I do I use the 'line reduction' to keep the main cuts from going all the way to the edges, then running a series of lower power/higher freq outlines to finish the edges--

I just drew this up as an example, but my numbers are pretty close. Also, I used black and blue cross hatches just for visual, in normal use I'd just use black for both hatches...

First 2 hatches are .05mm line spacing, 45 and 135 degrees...
for the first hatch I've added a .1mm line reduction--
f1.jpg

2nd hatch I entered a .07mm line reduction--
f2.jpg

The 3 hatch is a 5-line 'island' routine. To do this, I entered a "0" line space, this prevents a full-fill routine.
Then at the bottom, I've entered 5 in the NumLoops, and entered a tight loop distance of .01..
f3.jpg

This is the result....
f4.jpg

So what happens is, loop one runs but avoids the edge by .1mm,
loop 2 extends the cut by .03mm-- So the middle minus .1mm is hogged out, 2nd pass creeps out a snick farther...

Then the 3rd hatch runs its 5 lines from the actual edge and meets the first 2 hatches.

The trick is, to find the right speed, power and frequency of the island hatches, how many loops to run, and the spacing.

I've only done this a few times on some AR lowers, and haven't had time to experiment much, but it does cut the burr down a ton, and seems like a good compromise between fast-as-you-can hogging and slow-n-easy hogging...

[John Kleiber]

Like John, I'm in a hurry!

I have come up with a bit of a fix, doesn't eliminate the slag but it helps---

What I do I use the 'line reduction' to keep the main cuts from going all the way to the edges, then running a series of lower power/higher freq outlines to finish the edges--

I just drew this up as an example, but my numbers are pretty close. Also, I used black and blue cross hatches just for visual, in normal use I'd just use black for both hatches...

First 2 hatches are .05mm line spacing, 45 and 135 degrees...
for the first hatch I've added a .1mm line reduction--
f1.jpg

2nd hatch I entered a .07mm line reduction--
f2.jpg

The 3 hatch is a 5-line 'island' routine. To do this, I entered a "0" line space, this prevents a full-fill routine.
Then at the bottom, I've entered 5 in the NumLoops, and entered a tight loop distance of .01..
f3.jpg

This is the result....
f4.jpg

So what happens is, loop one runs but avoids the edge by .1mm,
loop 2 extends the cut by .03mm-- So the middle minus .1mm is hogged out, 2nd pass creeps out a snick farther...

Then the 3rd hatch runs its 5 lines from the actual edge and meets the first 2 hatches.

The trick is, to find the right speed, power and frequency of the island hatches, how many loops to run, and the spacing.

I've only done this a few times on some AR lowers, and haven't had time to experiment much, but it does cut the burr down a ton, and seems like a good compromise between fast-as-you-can hogging and slow-n-easy hogging...

Kev, I intend on trying your settings. This anodized marking job is due on Monday so I have not had time to test, but I intend to next week. Here is the serial marking I completed yesterday. Turned out pretty good, but I'm eager to try your settings.

My laser P/N and S/N are top. Customers tool engraving and hand engraving (yuk) bottom.

upstream_sleeve_part_marking.jpg