Engraving Annodized Aluminum

Thanks - I’ll have to give that a shot. I actually bought an ammeter just to see if the levels were different. With the same levels (~5-6 milleamps), I get very different results when comparing Cohesion to Nano…so there’s something else going on.

Like I said, it’s finnicky. I’ve seen where I can increase the potentiometer and decrease the percentage in lighburn (to keep the same number of milleamps), and my resulting work is much different (better). I need to get this resolved, because right now, it’s more of a crapshoot than science on dialing in settings that work.

I also noticed, now that I’ve got my ammeter set up, that for some settings, changing the % power in lightburn doesn’t materially change what shows up in the ammeter. For example, I was running at 70% max power in lighburn and seeing the ammeter show around 14. I bumped it up to 80%. Still showed 14. Up to 90%, still showed 14.

OK. The pot sets the maximum limit of mA. Light burn then controls a percentage of that. HOWEVER, the default smoothie firmware is capped at 80% power so LightBurn is only controlling a percentage of 80% of what the pot is set to. So 70% on a nano is not the same as 70% in LightBurn. It is actually 70% X (80% X Pot Setting) So if the Pot is set say to 10mA, the nano would put out 7mA but the C3D with LightBurn would put out 5.6mA I hope this is making some sense. You can edit the smoothie configuration file to be at 100% , and then the power settings you used with the nano would be the same with LightBurn.

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Thanks, Anthony for trying to help…I did set the Smoothie config file to 100% early on…just to make sure I was comparing apples to apples.

Is there a way to turn OFF pwm? Go back to just doing dithering/raster instead of getting a true grayscale? I’m sure grayscale/PWM is great if it works. But I just can’t seem to get it to work. I’m at least 50 hours deep in trying to get this board to work…and my lightburn 30 day trial is nearly up.

One last comment…in case it matters, the potentiometer is the digital one…not the dial.

A few quick notes just to get the conversation going again, this is intended more as a recap of this thread to make sure we are both on the same page, and then we can continue the conversation:

PWM does seem to be working, I do see quite some change in darkness in these. PWM Period of 200 or 400 is usually all that’s needed, but you seemed to be having sufficient enough contrast at the period of 200 (first pic).

By the way, overscan is definitely the thing to use to stop the “dark curtains” from happening on the edges of a scan.


Then, as you discovered, setting the pot lower allows for more detailed grays to come out.

We cover that here: Cohesion3D PWM Control and Potentiometer vs 'Digital Panel'


So there’s a few ways we could go forward:

  • It could be the LPSU either being “finicky” or “weird”.
  • The digital panel is less than ideal for true gray details, the analog knob does work better for setting the max power and then we can really dial in. When you say the overall performance is finicky, it could be because of this.
  • You at least have an mA meter now, so that’s good. If it is saying the same power as you expect consistently, then that is another argument towards “PWM is working properly”
  • We could rewire to bypass the digital panel entirely. It’s possible, it’s not my favorite idea, but it’s possible. I’ve got probably 1500 boards in the wild by now and this has never been necessary before.

Good recap. The only other thing I’d throw in is the disparity between the sample on the flashlights. T Highfill vs. Trey. While at some point in time I’ll probably be doing work in grays, right now I just want to engrave anodized aluminum as clearly and bright as possible. And the anodized aluminum is what is really giving me the problems.

With the Nano board, I’m getting a “pop” on the aluminum surface when the laser fires. I get a similar pop when running the potentiometer anywhere between 50% and 99.9%. The mA meter never gets over 10.

Seems like I never get that kind of pop with the cohesion board. Except for right on the edges (like you can see with the one that says Trey above). It’s almost like there’s a different amount of energy or frequency or something at the edges. If I run the pot at 99.9% and run lightburn at 100% power, my mA meter spikes up past 30. To keep it from spiking above 10, I’ve got to set the pot on 20%…which leaves the mA meter around 2 for most of the run.

I’m going through a lot of flashlights trying different settings…so if there’s a “focused” type of test you want me to run or something you want me to video, let me know and I’ll give it a shot.

Ran one last test tonight. In both, Potentiometer set to 99.9. Ztable at same height. Just rotated the flashlight between tests.
Top is with cohesion/Lighburn. Fill mode (you’d have never guessed it!). Speed 35mm/sec. Max power 100%. 1000 DPI. Smoothieware max power set 1. Actually ran over it twice, the brightness got a little more pronounced on the second run, but not by much.

Bottom is with Nano/K40. 35mm/sec. 1000dpi, .001 inches.

Any additional thoughts?

So, 1000 DPI is physically impossible and a myth propagated by certain people that do not know any better. 254 DPI is a good number to work with. 200-300 DPI is a good range to use. Above 300 DPI is where you begin trying to defy physics. The laser dot simply isn’t that small.

I was thinking a lot about whether the alternate PWM wiring would be worth exploring with you, and I don’t think it is. PWM appears to be working properly for you, which means that the board is working properly, and PWM is not the root of the issue you are having.

This is a settings game, mostly in LightBurn, but possibly some on the board like the acceleration values, to find what works for you.
The M2Nano does not have any sort of acceleration parameters so just because you specified “some speed” with that does not mean that a) it was actually hitting that max speed, or b) that the C3D board is reaching that max speed because it actually respects the accelerations set for it on the config file.

Unfortunately I don’t have any experience with engraving on anodized aluminum. I primarily cut engineering parts.

When we’re getting people set up, it’s the fairly basic stuff where engraving speed and pwm tuning are usually the last things we go through. By all measures, the board is working.

Fair enough…While I appreciate that you don’t engrave on anodized aluminum, it was the reason that I bought the engraver, this board, lightburn and the camera.

That said, how do I go about returning the board? If it is performing worse than the nano, and as the manufacturer you indicate that you can’t help, I’m not sure what else to do.

Setting the pot to 99.9 (spiking over 30ma as you said) is going to burn out your tube quickly, and can actually reduce the output power as well.

It looks like you are only getting outlines, which doesn’t make any sense. What format are your files, and how do they look in the preview window? What happens if you try to burn the exact same file with the same settings on a piece of wood?

I’m with you on running it at 99%…and normally don’t do it. But as a matter of testing, I’m trying anything. You can see in some of the earlier examples, though, that whether it is 99% or 70%, I get similar results.

If you look really closely, it isn’t “just” an outline. It’s almost like there’s a pulse at the end of the lines that makes it look like an outline. The very first picture in this thread shows it clearly.

For the “live confidently” example, I used an SVG file. But I’ve tried image files and also tried text tool from within lightburn and some of the other tools within lighburn (lines, squares, etc).

I’m away from my engraver till Sunday, but would be happy to run a test then. Is there anything in particular that would be beneficial to see? I’d be happy to do a ramp test if there’s one in particular you’d like to see on the aluminum.

I’m interested in this alternate wiring for the PWM. I have my pot set to 15% and in light burn the power is set to 1 and speed is 50. When I try to do a greyscale photo all I get is a dark black shape of whatever picture I try. I want to do the test you did with the grid squares. How did you do it? Is there a file that automatically adjusts the power for each square of is it a manual thing?

With the power set to 1% you’re using a very limited range of the power output. For grayscale images you’re better off setting the pot lower and setting the power in LightBurn to full, so the board is giving you the full range of output.

For example, Smoothieware uses 12 bit PWM, which means 4096 total possible output power settings. If you set LightBurn to 1% power, then run a grayscale image, you’re using 1% of that 4096 range (roughly 41 values) for an 8 bit image (256 possible values), so you’re losing precision. If you set the pot higher and used 10%, you’d have 409 possible power output values, which is more than necessary for an 8 bit image.

We can extend the trial again if necessary.

The things I’m interested in are:

  • The file you’re burning
  • The settings for the Fill layer
  • The preview of the file
  • What it looks like when burned on wood

The result you’re getting doesn’t really make sense, so I’m trying to figure out what’s happening. about 1% of these boards fail, so it’s possible, but it’s rare. In nearly every case we’ve seen where the customer swears they have a bad board it’s ended up being user error - either settings or wiring. So I can’t say for certain that nothing is wrong with your board, but I can say that statistically it’s unlikely, and we’re trying to eliminate the other things that it could be.

Here ya go. No need to extend the trial. I went on and bought it. I’m confident you’ll get me fixed up. :slight_smile:

First, a sample on K40Whisperer. Potentiometer was set to 80%. I used an SVG file that I created in Inkscape. Nothing fancy, just typed text. Settings in the first picture, results in the second.

For the Lightburn test, I connected the Cohesion board. I left the potentiometer on 80%. Didn’t change the z table. I used the text tool in lightburn to create the text. I’ve gotten similar results in the past using different formats/images. For this one, though, I thought I’d keep it simple using the tools within the app to hopefully at least remove one variable. You’ll see 4 shots below: Settings, preview, output on wood, output on the aluminum.

Note in the aluminum photo, while it looks like a “line”, you can actually see that it’s scanning…and the part that seems to take well is the outer edge of when you’d expect the laser to cycle on/off.

That makes total sense! I was going at it bass ackwards. I was lowering the power in the software and upping the power on the pot. I’m going to try it in reverse and see what it does…

UPDATE: I searched for a picture I took that would be a good test and I found one and printed it out on some birch plywood. It came out decent compared to my others. I used 100% power in the software and 5% on the pot.

There were some grey clouds in the pic above the skyline that didn’t print. Not sure why because they were grey enough to print. Just wanted to update on my greyscale printing. At least I know it works now…

For starters, turn off “Scan shapes individually” - that will get you to the point where the whole thing is scanning consistently, with the exception of the furthest left / right edges.

Try this as a test: turn off bi-directional scanning. To me, it looks like you’re getting a strong burn at the start of each line, but then the power drops off. I’m not sure why that would happen, but turning off bidir will verify that - You’ll get the strong spot only on the left, or right, depending on which way it’s traveling when it fires. Right now I suspect you’re getting a burn at the left when it’s traveling left to right, and a burn at the right when it’s returning, going right to left.

If you do a long-ish solid rectangle, what does the milliamp-meter do? Does it stay consistent, or does it spike at the start and then fall off again? (do you have a ma meter?)

On the wood burn you did, if you look carefully, does it appear to be shallower in the middles?

One thing I notice, you’re using a different interval in Whisperer and LightBurn - You have the Whisperer output set to 500 DPI, and LightBurn set to 338 - that’s going to put down about 35% less power on a given area, which might explain the difference in output.

Turned off “Scan shapes individually”
Turned off bi-directional scanning.
Changed DPI to be 500 to match Whisperer.

I couldn’t tell anything in the wood. I.e., didn’t seem to look any deeper/shallower in the middles. But admittedly, it would be pretty hard to see I bet. And my eyes aren’t that great.

I do have a ma meter. I wired it myself…so that is suspect. :slight_smile: I placed it in-line to the wire that runs to the tip of the laser. When I did the long rectangle, it pegged to the right (north of 30). To get it down to the 10-15 ma range, I had to drop the POT to ~30%. When I dropped it there, it was consistent across the whole rectangle. If I need to do more scientific testing on that, I can tonight. I could also try a long rectangle in Whisper and compare the outputs if that would help.

Here are the photos of the output with the settings adjusted like you mentioned. Turning off bi-directional did isolate to one side.

Here’s one last thought…and maybe someone on here knows more about it than I do. It does seem like the power output is different on the left side than the right. But wondering if it is “more” power…or “less” power.


Any ideas based on the test from last weekend?

Is your laser power supply screeching like a banshee when PWM is applied?