Fiber Laser Aluminum Consistent Depth Issue

[John Kleiber]

We have a 50w fiber laser and have an issue with consistency of depth while engraving bold text or specific large solid sections of graphics.

When lasering at 225 deg. depth is greater at the beginning then gradually a little shallower.

I have tried various angles, speeds and line resolutions... even a small fan to cool.

It seems running faster 350 speed and loosening up the resolution to .05 from .01 helps.

I an not experiencing this issue with other metals.

Is the aluminum heating up and as a result not uniformly atomizing.... I say that because on a 10 loop run, the first 5 loops have a bright white laser response..... but later in loop 8,9 and 10, there is less intense light.

To work around the issue I cheat and ad a couple of small metal pieces to shield certain spots from becoming too deep.

Thanks
John

[Gary Hair]

I'm betting you are getting out of focus and losing power in those areas, especially when you say you can see a noticeable difference in later loops. Every loop lowers the surface a bit and you might have to re-focus to compensate. It's also possible that you are very close to being out of focus to start and it doesn't take much depth to be out of focus. Focus is more critical at the extents of your working area so I've found a few occasions where I had to do some work in sections to stay closer to the area directly below the lens. I'm not a physicist, so I have can't say if the aluminum heating can cause problems with lasering, but I've never had that problem before so I'm more inclined to think it's focus related.

[John Kleiber]

I will try some incremental test runs and adjust to determine if focus is the culprit.
I did not think focus would be the issue because while running the engraving on stainless steel, as opposed to aluminum, SS yields no noticeable problems.
Nevertheless SS is definitely not aluminum so I will try focus.

Thanks
John

[Kev Williams]

do you cross-cut? I'm still learning to use mine, but I've found cross cutting works better than a one-angle pass.
And FWIW, I don't do 'loops' when cross cutting, because each successive loop repeats the same angle until the loop count is done before running the second angle. Instead, I just use the 'mark counter' or whatever it's called at the bottom. That way, if I want 8 passes, it'll run the 45, then the 315 eight times rather than run eight 45's then eight 315's... seems to be more productive that way.

As for the focus problem, just split the difference before you start; if you plan to go .016 deep, then start the cut de-focused by .008...

[John Kleiber]

Cross cut and focus. ok I will give that a try in the morning.

[John Kleiber]

Cross cut and focus. ok I will give that a try in the morning.

I made 2 videos this morning to illustrate the uneven depth issue and poor burning as the loops progress.

This is TEST 1, Test 2 to be posted after.

TEST 1: This video is a 15 loop pass, speed 160, power 100
Notice as it lasers, initially its super bright, then gradually the brightness fades and the laser just dances on there surface.

https://youtu.be/RUZJ4tpFxWw


-John

[John Kleiber]

I waited approximately 2-3 minutes and performed the following second test using the same settings.
TEST 2: This video is a 15 loop pass, speed 160, power 100
Notice as it lasers, initially its super bright, then gradually the brightness fades and the laser just dances on there surface.

https://youtu.be/WePHAkh07Uk

I do not have this issue with stainless steel or other metals, only aluminum.
It has been suggested that focus could be an issue.... but why is it I get a nice bright white light during laser at the beginning of the run, then not. Wait 2-3 minutes then same thing, bright then dim?

-John

[John Kleiber]

Kev,

Not sure of the version you are running of EZCAD2, but I cannot find any reference on screen or in the manual regarding "cross-cut" or "mark counter"

My version is 2.12.0

Thanks
John

[Gary Hair]

I waited approximately 2-3 minutes and performed the following second test using the same settings.
TEST 2: This video is a 15 loop pass, speed 160, power 100
Notice as it lasers, initially its super bright, then gradually the brightness fades and the laser just dances on there surface.

https://youtu.be/WePHAkh07Uk

I do not have this issue with stainless steel or other metals, only aluminum.
It has been suggested that focus could be an issue.... but why is it I get a nice bright white light during laser at the beginning of the run, then not. Wait 2-3 minutes then same thing, bright then dim?

-John

I'm not sure why you have this issue with aluminum and nothing else. I ran a quick test with your settings on my 30 watt machine and I get a very bright flash the entire time it's running and some pretty serious depth. How deep is the mark you get after 10 loops?

[John Kleiber]

:)

I've made some progress. I have adjusted speed with some slight improvement... but FOCUS seems to be the culprit.
What thew me off was how well other materials laser'd well despite the laser slightly out of focus.
It's also weird in that, why would it laser ok during the first few passes, then fade.
It seems like if the laser were out of focus, the laser process would of been consistently poor.
I have no idea when the focus got out of wack. So far in testing, it's doing great and my laser time is 1/3 the time it use to be.

At least in this situation, it seems a symptom of a laser out of focus is a correct removal of material to proper depth in the outer area of the laser and less so to very little in the more central less focused part.

I drew up this diagram. I was engraving 2 lines of text and I noticed a depth inconsistency. Toward the outer edges, engraving was the correct depth, however the text toward the center was shallow.

In the diagram, out of focus in red, only becomes focused towards the outer edges.

344660

-John

[Gary Hair]

How did you determine the focus distance when you got the machine? Did the manufacturer provide you with a measurement? It seems like most of them have you laser a piece of hardened steel then raise and lower the head until you get the brightest flash - that should be in focus. I found that doing this with a square drawn at a size equal to the extents of my working area gave me the most accurate measurement due to the fact that the outer edges are more critical of focus than the center.

Are you lasering directly under the galvo head? If so, that should be the most forgiving place in your entire working area.

[John Kleiber]

How did you determine the focus distance when you got the machine? Did the manufacturer provide you with a measurement? It seems like most of them have you laser a piece of hardened steel then raise and lower the head until you get the brightest flash - that should be in focus. I found that doing this with a square drawn at a size equal to the extents of my working area gave me the most accurate measurement due to the fact that the outer edges are more critical of focus than the center.

Are you lasering directly under the galvo head? If so, that should be the most forgiving place in your entire working area.


Gary,

The installer did adjust the laser for steel at the time and we also did aluminum. However, while configuring the rotary I managed to break something in EZCAD2's settings. So I restored EZCAD2 and performed the focus process on steel myself, but unfortunately I did not test aluminum. Now I have tested both, the laser light is super bright and I get a nice ripping sound during lasering. :)

-John