CerMark Striations/Inconsistencies

[Jonathan Groves]

I've been using CerMark LMM14 and LMM6000 for about 3 months now and am starting to notice some inconsistencies and vertical striations on our products we are marking. The issue only seems to occur where there may be a larger area that is being engraved and after engraved and washed, the result shows differing shades of black horizontal lines. I've attached an image showing what I mean.

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I have an 60w Epilog Helix and we've seen these inconsistencies at 40s 100p and 30s 100p as well as with the LMM14 and the LMM6000.

Can thickness of the CerMark be a factor for something like this? I'm at a loss of what to do and customers are not happy and I can't blame them...

Any help would be super appreciated.

[Kev Williams]

Banding, caused by the beam wobbling and overlapping.

My GCC and LS900 are horrible banders...
After cleaning all the mirrors on the GCC last week, I thought I'd give this leather a shot with the extra power...
While the power picked up, I was hoping the banding might decrease- as you can see, it did not!
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-My LS900 is just as bad. Funny thing is, the machines show banding differently- My LS900 will band large areas of black anodized aluminum badly, but the GCC doesn't band anodized at all.

There are various reasons for the banding. The most intriguing explanation I got was from the New Hermes boys, who said it's by design, to help with photo engraving. I thought it was a lame excuse, but it was hard to argue after these tests- this piece shows the top 3 lines of rastering at 50 lines per inch at different speeds. They all wobble, but differently. The bottom line is vectored at full speed- which isn't real fast, but there's no wobble at all. The real kicker? Each of these test were engraved TWICE- all lines exactly repeated themselves!
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--this pretty much rules out a mechanical issue, or a power supply issue, which are other causes...

This is another sample piece, where the top line is done at normal res levels, the bands are very obvious...
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Back to banding differently-- Neither of my machines cause any banding at all on Cermark. None. Your machine seems to be roasting the Cermark in the banded areas. But you also have substantially more power than I do. Now, my Triumph can cause burnt Cermark like that, just depends on the power settings.. and speed...

Which brings me to some advice... I bought the Triumph very much hoping that I could do Cermark much faster. Didn't happen...

I've come to find that Cermark likes to be engraved SLOW, and it doesn't necessarily like lots of power (it don't like my Triumph at all) You're engraving at 40 and 30% speed. The fastest I engrave with both my GCC and LS900 is 18% speed, at 600 lines per inch. Very different machines, but they both have roughly 70 in per second top speeds, and the lower speeds are pretty close to each other. I'll assume your machine should be close to the same, if not faster actually...

Ran these cups yesterday on the GCC, 18 speed, 100 power, 600 lines per inch. Not nearly as big a logo, but still, no banding or any inconsistencies--
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OK, some ideas: Slow your machine to 18 speed and reduce power to 60%, 600 lines per inch. I'm betting just that will get you a noticeable improvement...

If you're still showing bands, try the fix I did for the leather: I went 50% black, and ran the logo in halftone. I also slowed the machine down. At 50% black, you CAN, and may need to raise the power to compensate. Also, the GCC seemed to like 50%, anything above still banded. My LS900 likes 70% black.

I suspect you have a halftone or 'photo' mode that will run lower blacks automatically-- if not, use Corel to create a bitmap at 300 dpi if needed...

The whole purpose of less than black is because the dithering breaks up the beam's firing due to the white spaces. Less firing means less beam overlap, and much less or NO banding!

Hope some of this helps :)

And YES on Cermark thickness, you could probably thin yours out...

[Jonathan Groves]

Thanks for the detailed response! I've never had "banding" issues with anything other than the CerMark. The high power could be the culprit since it only happens on areas with a lot of black which means concentrated heat in a specific area. I could see how that could cause the roasting issue. We will give it a try at different settings as well as thinner coats of CerMark and see how it goes. Thanks again!

[Jonathan Groves]

Had some free time tonight so I sprayed up one of our "mistake cups" and engraved bars at different settings. As you said, Kev, the settings were the issue. I engraved at 30s100p, 18s60p, 30s70p, and 60s100p just for kicks. The results were very interesting.

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Overall, I couldn't tell much difference in the 18s60p and the 30s70p. The 60s100p I did just to see what would happen. It strangely looks blacker than the others, however, you can see streaks of metal through the black where the "grain" of the metal is.

All in all, after this test I think we've decided to do 30s70p just so we cain maintain our speeds. I just engraved a logo that was streaking on me bad with these settings and it looks perfect. Thanks for the suggestion!