My Cermark nightmare

[Allen Rawley]

In my experience with Chinese glass tube lasers and metal tube lasers and Chinese machinery/controls, the following factors may affect the results with Cermark. We had attempted a production job with Cermark on stainless steel using a Weike 60 watt and gave up after many tries and washing off the steel pucks, and eventually switched over to use the Synrad F100 (set at lower power than max) to run the job. The problems we had included variations in laser power (some worked and some did not and some on half the job) and image quality was poor at times (actually it was all over the place).


First, a glass tube laser does not have a set polarization, like a metal tube laser. For those of you unfamiliar with polarization, think of it like polarized sunglasses, where only half the sunlight gets to your eyes and it is in one orientation, and if you were to put a second set of the same sunglasses together, but at 90 degrees off then no light goes though and you see only black. So, with the metal tube lasers, they are polarized in one direction (like a Synrad 48J-2 25 watt) or a combined tube (Synrad 48-5 50 watt) has two set polarized tubes combined. The point is that the glass tubes are not locked on polarization so haphazardly, during laser operation the polarization is rotating. What this means is that the temperature is changing in the nonround beam that goes to the material surface during the job. To test this in operation, you can put a polarization window at the proper angle and heat up something like a piece of metal and use your Fluke meter with its temperature gauge and watch the temperature change over time, it will go up and down and up and down and up and down.

A second factor may be the control system. Typical higher quality American controllers use a first pulse suppression technique, where the first pulse out of the laser spikes to a higher power relative to the rest of the subsequent pulses, so it is blocked out. Another controller difference is that the glass tube lasers run using a PWM signal. What this means is that the high voltage laser power supply is getting an average power by pulsing on and off. For example, when you run the Triumph 80 watt and it is set to 40 watts, then over time this is a square wave turning on and off half the time, say in one minute. These high voltage power supply can cycle on and off at a much slower rate than the metal tube (RF powered) lasers, and perhaps enough that you are seeing the effect in the Cermark. The Synrad, F series, for example, use a 25 KHz cycle, that is much faster than the 2000-5000 range for the high voltage power supplies. Now, combine that information, with the laser rastering. When you raster, there is a separate signal that enables/disables the high voltage power supply. So, if this signal is set on, while the averaging pulse is set off at the start of your engraving, then you may get a rough edge.

[Kev Williams]

I'm back!

Ok, first off, Gary said "I don't understand why you're changing the power"... If you're referring to the power grid, that was the first time I've done one, I was just doing what Scott suggested, and sorta copied the grid from the Cermark website. Also, this laser is a beast, you simply can't just run it at full power! This afternoon I did a semi-3D test engrave of a photo of a rose in oak, ran it at 400 speed and 50 power, and the black sections went nearly an 1/8" deep- Running my LS900 at full power and 20 speed would take 5 passes to get that deep! As for the power my Triumph does have, after a little research I found that Reci tests their tubes at 30mA. My supposed-to-be 80w tube at 30mA put out 110w, and the "agreement" power was 90w, which (I assume) is approximately the output at the 27mA suggested maximum. Sending a 70% power instruction to my laser when running a solid black raster line puts my meter right at 27mA. 73% puts it at 28mA, and I was noticing the other night that a 30% power instruction the meter was hitting 14mA. If actual output power is relative to the power meter (is it?), then my 30% power translates to around 45-50 watts output. From there the power falls off big time, like it did from 30% to 20% on my grid in the 500-speed column...

Second, I ran another grid, using different focus points. Pic is below, and I had some goofy issues at first so it's a bit weird in spots ( )




It's pretty tough to make out much from the pic but I DID decrease the contrast so the blacker sections would show up better. The numbers are the focus distances of each test.

First thing that really stands out is that, in the middle sections, nearly all of the 1.32's are blacker than everything else! In the upper-leftish area, too much power makes all the numbers too gray. From 40 power and below, the other numbers start getting darker, because the the higher focus numbers are closer to the 'actual' focus point of 1.48", and the extra heat seems to help. And 1.32 is about useless below 30 power. And like before, speaking of power, I have pretty good results at 35 power, but almost zilch at 25 power.

I expected better from the 1.38 numbers, they're the worst in nearly all tests. Cermark, with this laser at least, likes the lens closer. But one issue with the nice black 1.32's is they're a teensy bit thicker than the others. So I've pretty much settled on 1.35" as the focus sweet spot. And the best overall 1.35 number group I can find on the plate is 35 and 40 power at 400 and 450 speeds. I ran another panel at 450 speed and 38 power and it came out just beautiful. And while it warped, it wasn't nearly as bad. And FWIW I goofed on the thickness of these panels, they FEEL like 1/8" but they're actually only .080 thick.

So I'm pretty zeroed in with the Cermark now, so I'm happy! I guess what I'm having a hard time figuring out is why the radical difference in focus points between a nice crisp marking on anodized vs. getting Cermark to work? Just to make sure I'm not crazy, I just did a test- top row was focused at 1.35", bottom row focused at 1.48". That's over 1/8" difference...?




================
I have 3 lasers and they're all pretty different. I've always had consistency issues with my 25w ULS doing Cermark so I did a power grid with it today. And I found out why I've been having issues; the power/speed settings that actually work well with Cermark are extremely limited... I found it's sweet spot at 100 power and 23 speed. Slowing down 4 points to 19 speed, the laser boiled the Cermark. Speeding up to 27 speed, the Cermark would barely stick! That's not much range to play with! A couple of 90-95 power/speed settings will work, but I see no reason to slow it down! I've been running a bunch of small ID tags since I ran the test and they've all been perfect! I definitely recommend a power grid test! And maybe some of you guys with Chinese lasers might try some radical focus changes?

[Jonathan Bowen]

I have basically no experience with this stuff other then a few test runs for a project. I did however have a lot of trouble with 2 tone acrylics. I think what I had was 1/32". It was warping on me bad and that material is super expensive. I finally figured out I could set my laser to only etch on one direction. Takes forever but I had amazing margins on that job. Wish my buddies company didn't screw him over. He stopped taking orders for that product they were used on out of spite basically. Guy does a few jobs for over half a mil per year and you'd think they would just let him do his thing.

Anyway not sure if that is any help at all but it was a simple fix and it worked for me. Now if I could just stop blowing tubes every 6 months...

[Dan Hintz]

I've always had consistency issues with my 25w ULS doing Cermark so I did a power grid with it today. And I found out why I've been having issues; the power/speed settings that actually work well with Cermark are extremely limited... I found it's sweet spot at 100 power and 23 speed. Slowing down 4 points to 19 speed, the laser boiled the Cermark. Speeding up to 27 speed, the Cermark would barely stick!

I am questioning your testing methodology (not as you state it, but how you're actually running it... the things we can't see and the things you may not notice). On my 60W ULS, my speed was roughly the same as yours @500dpi on a 31mil piece. You're less than half of the power on a piece that's nearly 3 times as thick. Are you testing the durability of your marks with steel wool? I'm beginning to think the wide variance in "good" marks is because you're not even close to the "good" mark range yet, and your marks are just waiting to rub off.

[Scott Shepherd]

I agree with Gary, where's the chart with max power? You keep posting charts with the power cranked down. Keep the power up and the speed down, not the speed up and the power down. My guess would be running it at your 80% recommended power (or whatever that reading is that tells you not to run it any hotter), and then start with too speed and work your way down in speed. On our Trotec, running 82w, on stainless, we're at 100% power and about 50% on the speed, if I recall right from memory. That probably translates to about full speed on your laser. So full power, full speed. Start there and work down on the speed.

Just my opinion. And there is no reason for it not to be in focus. There's something wrong going on there. Think about it, it's optics, it's either in focus or not, and it's going to be the biggest power density when it's in focus, not out of focus. There's something else going on there that you need to resolve.

[Ross Moshinsky]

I don't see how it can be ignored that the Chinese machine's max speed is 20in/sec and a normal laser's max speed is 80in/sec. That's why "normal" isn't working here.

50% speed on a 140in/sec is 70in/sec. A "normal" laser would be at 100% power (80w) and 80 speed (64in/sec). 6in/sec difference falls right in line with the margin of error Ferro gives. Go try to find the best settings for Cermark on your machine assuming you can't go faster than 15%. You probably won't run at 80W. That basically shows why the 30-50 power setting at 20in/sec works the best. The laser doesn't move fast enough to mark Cermark using the full power of the machine. Pretty much means if you buy a Chinese laser to use Cermark, you might as well only get 50-60W because any more than that, you can't use.

[Kev Williams]

Ross is correct, my machine is quite slow- and machines are different. I run Cermark at 14 speed in my 40w LS900, 23 speed in my 25w ULS. Part of the reason for the difference is the 900's 14 speed is nearly twice as fast as the ULS's 23 speed. Another reason must be the power-to-speed ratios of different machines aren't going to match at all. I mentioned in another thread that I borrowed an identical ULS to mine to run a rush job. I had to add more power and less speed to the borrowed machine to do the engraving, yet the hole cutting settings were identical to each other.

As for me not using max power, the 60% power shown on my test grid equates to 90% of my laser's recommended peak. And as Ross mentioned, my max speed is probably around 20% of a Trotec. And being a 51" long machine, I prefer the engraving quality of slower speeds (at least until I get it further tweaked to suit me). When I hit Cermark hard with the power, all I've ever gotten is lovely, beautiful, durable goldish-gray text that becomes invisible when the light hits it at angle. I can't have invisible engraving on my stainless, it needs to be as close to black as possible!

Have I tested my markings with steel wool? I occasionally test with scotchbrite, but why fool around? How about a real test? -- say, a nice healthy dose of 80 grit sandpaper attached to my trusty HF straightline sander...





Yes, I lost a few of my "good" numbers, but I don't have to go far to get the better ones... And while the upper numbers really stood up to the sanding, they should, they had mega-heat fusing them to the SS! However, durable as they may be, those images were totally unacceptable to me, they were nowhere near black, and would have no contrast against reasonably shiny #4 finish SS. The sanding taught me another thing: I should be leaning more towards the 1.38" focus point...


While in between typing all this, I did a test with my 2 larger machines. I used an old chunk of yellow/black NON-laserable Rowmark that I've been practicing on since I got the Triumph. I ran a full power/full speed pass with the Triumph, and did the same with the LS900. The Triumph was about .005" shy of a complete burn thru (last pic is the back side), and the 900 barely made a mark. So yes, there's a reason I've been having trouble hitting the Cermark sweet spot! This is definitely a Tim Allen machine!