Cermark in my LS900 vs my Triumph

[Kev Williams]

I brought this up when I first started doing Cermark in my 80 watt Triumph.

The short version: The Triumph literally incinerates the Cermark, and with very little effort. This turns it a dull, medium gray. A very NICE, and PERMANENT dull medium gray I might add. However, I don't WANT gray, I want my Cermark BLACK!

This is what's puzzling: My 40 watt Gravo LS900 will NOT turn Cermark gray no matter how hard I try. 100 power, 0 speed (which is about 1mm per second), 1200/1200 dpi/ppi won't do it. The Cermark ends up jet black. Same with my 25 watt ULS, but no surprise with the lesser power.

With the Triumph, running at 400mm/s and 40% power with the 2" lens in focus, no black. The only way I can get black is to defocus the lens closer by .100", and run around 350mm/s and 45% power. FWIW, 45% hits about 12mW on the meter, which I figure is somewhere in the 40-50 watt range.

I've gotten pretty good results using my 4" lens, but it'll fry the Cermark too. But I have more leeway with focus. I did a large logo last night, lots of black, it started out black, ended up gray. This is because a slight reverse-warp in the panel flattened out as it etched, which moved the focus point farther away. Pretty touchy. And why I'm posting this!

The setting adjustments I haven't really tried yet is to go much slower with less power. Like, 200 speed, 20% or so... My LS900 likes 16 speed/500lines/800dpi at 100% power. A rough guess on speed is about 100-125mm second.

I know there's gotta be a better sweet spot!

>edit< added this pic-- Note that "made in the usa" and the Crystal logo were done in the LS900. As you can see, they're jet black. Everything else was done in the Triumph, and it's NOT jet black. Look at the tops of the SKY, you can see it's blacker, then transitions to more gray. I did the logo at 450mm/s at 40% power, .07 gap, and defocused .06". As the panel flattened, the lens came more into focus, and cooked the Cermark.


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[Dave Sheldrake]

The way DC tubes resonate is totally different to RF Kev, the beam quality and mode of an RF is far better also

cheers

Dave

[Ross Moshinsky]

I think this is the last time I'll post this but: lasers use a ratio of power:speed.

Cermark's ratio is 80ips:100W.

510mm/sec = 20ips.

20/80 = 1/4. 100*1/4 = 25W

So you should be running at 510mm/sec: 25W

Basically you're too slow and too hot.

[Dan Hintz]

I think this is the last time I'll post this but: lasers use a ratio of power:speed.

Cermark's ratio is 80ips:100W.

510mm/sec = 20ips.

20/80 = 1/4. 100*1/4 = 25W

So you should be running at 510mm/sec: 25W

Basically you're too slow and too hot.

Such a statement makes several assumptions not specified... use of a 2" lens (i.e., a 5mil spot size), a good-quality beam as from an RF tube, a thin substrate with a low coefficient of thermal conductivity, etc. Using a DC Chinese tube to mark a thick copper plate is significantly harder to mark than using a Western RF tube laser to mark a thin piece of stainless steel. In other words, they really need to specify the power density needed for a good mark, but I doubt many would know what to do with that info if they had it. Catch-22.

My quick in-the-head calcs say he's not hot enough, but converting to mm/s and back, different power than what I'm used to, etc. can easily make me forget to carry the one. I'll do some on-paper calcs here in a sec to verify.

[Dan Hintz]

By my calcs, you should be around 700mm/s @100P for an 80W. The caveat is this assumes a quality beam from an RF source, so you may need to go slower with your DC tube, but that should be a good starting point to make a set of test squares. If you need to go slower, reduce the power in the same ratio. If you're not at the correct speed/power ratio to begin with, it will make zero difference how you turn the speed/power up/down, it won't mark. You need to find the sweet spot before adjusting both parameters at once.

You make mention of the Cermark looking black on one machine and gray on another... have you scrub tested all marks with some sandpaper? If it takes you hard scrubbing with sandpaper to get rid of the mark, that's a good mark... if it comes off with a few light swipes of a Brill-O pad, you're not adhering to your substrate and your settings are incorrect.

There can be NO warp in your substrates... anything more than 10-20mils out of focus and you're risking losing the sweet spot! Cermark must be consistent in its heat input to get a good mark... if you have warp, you will get good adhesion only at the point of focus, and the rest can flake/rub off.


I brought this up when I first started doing Cermark in my 80 watt Triumph.

The short version: The Triumph literally incinerates the Cermark, and with very little effort. This turns it a dull, medium gray. A very NICE, and PERMANENT dull medium gray I might add. However, I don't WANT gray, I want my Cermark BLACK!

This is what's puzzling: My 40 watt Gravo LS900 will NOT turn Cermark gray no matter how hard I try. 100 power, 0 speed (which is about 1mm per second), 1200/1200 dpi/ppi won't do it. The Cermark ends up jet black. Same with my 25 watt ULS, but no surprise with the lesser power.

With the Triumph, running at 400mm/s and 40% power with the 2" lens in focus, no black. The only way I can get black is to defocus the lens closer by .100", and run around 350mm/s and 45% power. FWIW, 45% hits about 12mW on the meter, which I figure is somewhere in the 40-50 watt range.

I've gotten pretty good results using my 4" lens, but it'll fry the Cermark too. But I have more leeway with focus. I did a large logo last night, lots of black, it started out black, ended up gray. This is because a slight reverse-warp in the panel flattened out as it etched, which moved the focus point farther away. Pretty touchy. And why I'm posting this!

The setting adjustments I haven't really tried yet is to go much slower with less power. Like, 200 speed, 20% or so... My LS900 likes 16 speed/500lines/800dpi at 100% power. A rough guess on speed is about 100-125mm second.

I know there's gotta be a better sweet spot!

>edit< added this pic-- Note that "made in the usa" and the Crystal logo were done in the LS900. As you can see, they're jet black. Everything else was done in the Triumph, and it's NOT jet black. Look at the tops of the SKY, you can see it's blacker, then transitions to more gray. I did the logo at 450mm/s at 40% power, .07 gap, and defocused .06". As the panel flattened, the lens came more into focus, and cooked the Cermark.

[Kev Williams]

Well, the DC lasers are a totally different animal, that much I've figured out. As for my Frenchie LS900, I have to engrave much slower than the calculations or it simply won't stick.

I did some test runs this morning, I put the laser IN focus for a change, started at 250mm/s and 18 power. I engraved "TEST RUN" in times roman regular at 1/4" high. Times is a good test because of the small serif details.

18 and 20 power proved not enough, I scrubbed it off with a paper towel.

I went to 21 power and lowered the lens to focus minus .030". The details got fatter, and still wouldn't stick.

I went to 23 power, and raised the lens to focus plus .010", and THAT combo worked pretty good. However, for long horizontal expanses, it's too hot. See the pic, the 'dash' is too gray. And worse, even the longer horizontal expanses of the text are too hot, while the shorter areas of the text are near perfect. But if I lower the power, then the long parts will be okay but the short parts won't stick.


Which means, I've pretty much decided that there is no 'sweet spot', and it's impossible to get satisfactory BLACK Cermark results with this machine. I guess that's where a nice, pulsed RF laser shines over a DC laser.

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[Dan Hintz]

Stop testing with text! Start with a power grid to create a baseline. Use 100% power to start. Find the proper focal point for your lens and stay there.

Without a proper baseline, all other tests are a complete hunting game. When, and only when, you get a proper baseline, then we can start helping you tweak for images/text.

[Gary Hair]

Stop testing with text! Start with a power grid to create a baseline. Use 100% power to start. Find the proper focal point for your lens and stay there.

Without a proper baseline, all other tests are a complete hunting game. When, and only when, you get a proper baseline, then we can start helping you tweak for images/text.

The nice thing about banging your head against the wall is that when you stop it feels really good!

[Dave Sheldrake]

Well made DC is great, but they end up in the same price range and life as a similar RF.
Other than the ZX series EFR tubes pretty much every tube out of China is a "Make do"

cheers

Dave

[Kev Williams]

I've done power grids and ramp testing.

According to my ramp tests, my sharpest focus with my 2" lens is 1.49" to the bottom of the lens barrel (the lens itself is nearly 1/2" farther up the barrel).

I grid tested from 25 to 60 power in 5% increments, and 250 to 500mm/s in 50mm increments. I did all tests at 1.32", 1.35", and 1.38" focus. According to my grid, to get a good black mark I have to focus at 1.32". Beam width must be pretty fat at this point.

At 1.32" focus my power grid sweet spots are 450-500mm/s@60 power, 400-450@55, 350-450@50, 300-400@45... At 1.35" I got so-so results. At 1.38", in every test it cooked the Cermark except 300-400 @ 30, and 250 @ 25 power. At 25 power above 250 speed, the Cermark rubbed off. At 35 power, any speed, it's cooked. And the closer I get to actual focus, the easier it is to cook. Just not seeing much of a happy-medium here.

I used my 4" lens a couple of weeks ago and got okay results, I need to do a grid test with that lens, maybe I'll get lucky...

[Dave Sheldrake]

I used my 4" lens a couple of weeks ago and got okay results, I need to do a grid test with that lens, maybe I'll get lucky...

The 80 watt has quite a fat incident beam from a RECI tube so the final spot will be a lot smaller in a shorter focal length lens, this is going to mess up the power density correction factor (it's going to focus all the power to a small spot) moving to the longer focal length will scatter the beam to a bigger spot and lower the power density.

This is demonstrated by the *better* results with the longer focal length and better results when the beam is run *off focus* so lowering power density.

In essence Kev, you are pumping too much power from that tube for the shorter focal length lens to be useful

cheers

Dave

[Dan Hintz]

According to my ramp tests, my sharpest focus with my 2" lens is 1.49" to the bottom of the lens barrel (the lens itself is nearly 1/2" farther up the barrel).

I grid tested from 25 to 60 power in 5% increments, and 250 to 500mm/s in 50mm increments. I did all tests at 1.32", 1.35", and 1.38" focus.

You seem unwilling to create a proper baseline for all further experiments. As such, I am unable to help.

I give up.