Black v Gray Cermark, whuuuUUTT?

[Kev Williams]

OK, so for going on 5 years I've had issues with my 80w RECI-Chinese Triumph producing grayish rather than blackish Cermark results. My Gravograph 40w LS900 and the 30w GCC Explorer both give me stellar black results. Both have Synrad lasers in 'em...

I just bought a new (to me) Gravograph 35w LS100, which tested at 45 watts.

So it's been much to my chagrin that this new laser is giving me the same exact results as my Triumph rather than my other 2 Western machines!

One difference: Coherent laser this machine, Synrad's the other two.

Since I can't have two machines that don't do stainless, I decide to run some tests at varying power levels, to see if too much power is an issue...

And something really weird and unexpected just happened:

First, here's the test pieces:
394930
394931
394932
first, the two "laser test"s in the middle were done long ago with the LS900 for reasons I forget ;)
The top line tesT(s) were done with the LS100, between 90 and 60% power, same speeds, not much change, but--
In pic one shot straight-on, the top line is noticeably grayer compared to all the others.
The bottom 2 pics show how it gets worse as the plate is angled-- ICK!!

BUT, the tesT's in the very middle, they're nice and black! At all angles! Perfect!
but, how it happened was the weird and unexpected part because--
-- that line is engraved with the same exact settings as the top line!

I made one tiny change, what was it? :D

(and I'm very much hoping it works for the Triumph!)

[John Lifer]

Hmm m. Focus

[Kev Williams]

Nope, both versions in sharp focus... but you're in the ballpark ;)

And, I'm testing the Triumph, I'm hoping...

[Gary Hair]

top to bottom vs bottom to top

[Scott Shepherd]

Lens size (focal length of the lens)?

[Kev Williams]

:) Ok--

what I did: Swapped the lens from the LS900 to the LS100. That's it... !

To test the results I put the LS100 lens in the 900, and I got gray engraving -- Definitely the lens!

And late last night I put the Explorer's lens in the Triumph, and lo and behold, for the first time ever, the Triumph produced nice black outlines on one of my big SS operator panels! Holy crap!!

I'm elated! Now, I knew there was a difference between $18 lenses and $300 lenses, but I had no idea just a lens change would make such a night & day difference with Cermark! I've tried probably 10 different Chinese lenses the Triumph, different 1.5", 2", 2.5", 3" and 4"ers, and a couple of 1.75" GaAs lenses, never gotten black Cermark with any of them. Likewise, I've used a couple of the Chinese lenses on the LS900, and they worked great, but I wasn't doing stainless. Just found this out by accident!

So I'll be asking my rep why the LS100 lens acts like a cheap lens? It's flawless to look at and engraves everything else beautifully, but maybe it's been replaced?

Final question then, if I spring for a couple of $300 lenses, how will I know they'll be the ones I need?

[Scott Shepherd]

:) Ok--

what I did: Swapped the lens from the LS900 to the LS100. That's it... !

To test the results I put the LS100 lens in the 900, and I got gray engraving -- Definitely the lens!

And late last night I put the Explorer's lens in the Triumph, and lo and behold, for the first time ever, the Triumph produced nice black outlines on one of my big SS operator panels! Holy crap!!

I'm elated! Now, I knew there was a difference between $18 lenses and $300 lenses, but I had no idea just a lens change would make such a night & day difference with Cermark! I've tried probably 10 different Chinese lenses the Triumph, different 1.5", 2", 2.5", 3" and 4"ers, and a couple of 1.75" GaAs lenses, never gotten black Cermark with any of them. Likewise, I've used a couple of the Chinese lenses on the LS900, and they worked great, but I wasn't doing stainless. Just found this out by accident!

So I'll be asking my rep why the LS100 lens acts like a cheap lens? It's flawless to look at and engraves everything else beautifully, but maybe it's been replaced?

Final question then, if I spring for a couple of $300 lenses, how will I know they'll be the ones I need?

You don't need to spring for $300 lenses. Go to ii-vi and you can call them. Tell them the diameter and the thickness and they'll match it to what they sell. They supply lenses and mirrors to everyone in the business. I think my first (and only) lens I bought from them was about $125. I think it was $145 or something and they had a first time buyer discount so it ended up being $125. Top notch company, very good people, very smart.

[Mike Null]

+1 on ii-vi

[Ian Stewart-Koster]

Amazing to read about the differences...Thanks for the story, Kev.
But we use ii-vi here also.

[Kev Williams]

Then I'll have to give them a try, I can see where they'll need to special-make any lenses I'd want, none of their in-stock lenses are even close to what fits a typical laser engraver...:)

funny thing, I've only bought lenses for the Triumph, all of my western machines, including the 21 year old ULS are on the original lenses...

[Gary Hair]

Then I'll have to give them a try, I can see where they'll need to special-make any lenses I'd want, none of their in-stock lenses are even close to what fits a typical laser engraver...:)

funny thing, I've only bought lenses for the Triumph, all of my western machines, including the 21 year old ULS are on the original lenses...

They stock every size you could possibly need Kev. I know the GCC takes .75" and the one you have in the laser, or at least had in the laser, was a stock lens from II-VI. Check eBay there are a lot there - 19.05mm is close enough to fit, at least in the GCC anyway.

[Kev Williams]

If that lens is a ii-vi then I'm sold :) -- it's a hair under 3/4", maybe .71 as that comes to 18mm... a 3/4" does fit in the holder okay, I've used a 1.5 in it a couple times...

Their website's size listing's don't show anything close to laser-engraver size, at least this page doesn't, goes from 1/2" dia. straight to 1", and then nothing but bigger!
395068

--going to hit ebay..

[Scott Shepherd]

If that lens is a ii-vi then I'm sold :) -- it's a hair under 3/4", maybe .71 as that comes to 18mm... a 3/4" does fit in the holder okay, I've used a 1.5 in it a couple times...

Their website's size listing's don't show anything close to laser-engraver size, at least this page doesn't, goes from 1/2" dia. straight to 1", and then nothing but bigger!
395068

--going to hit ebay..

Kev, just call them. They are a huge company with a huge inventory. Just call them with the use and dimensions and they should be able to match your needs.

[Gary Hair]

Those are meniscus lenses and you want Plano convex.


If that lens is a ii-vi then I'm sold :) -- it's a hair under 3/4", maybe .71 as that comes to 18mm... a 3/4" does fit in the holder okay, I've used a 1.5 in it a couple times...

Their website's size listing's don't show anything close to laser-engraver size, at least this page doesn't, goes from 1/2" dia. straight to 1", and then nothing but bigger!
395068

--going to hit ebay..

[Scott Shepherd]

The part number I have for a 3/4" diameter, .080" thick, 2" focal length lens is 488614.

[Kev Williams]

Now, according to their website, seems I don't want plano-convex:

"Plano-convex lenses, the most economical transmissive focusing elements available, are ideally suited for laser heat treating, welding, cutting, and infrared radiation collection where spot size or image quality is not critical."

--I'm kinda thinking for my needs, spot size and image quality IS critical! ;) Their description of meniscus's...
"Meniscus lenses are designed to minimize spherical aberration producing a minimum focal spot size for incoming collimated light."

Virtually all laser engraver lenses for sale on ebay are meniscus lenses-- and of all the plano convex lenses for sale on ebay, almost all were clear not yellow, and for totally different machines and/or purposes...

I did buy 3 ii-vi lenses off ebay yesterday, two 2"ers and a 2.5"er, so I'll be reporting back with results when they get here... :)

[Gary Hair]

Hopefully you didn't order meniscus - they are not what any laser we (the "royal we") use.

https://www.quora.com/Whats-the-difference-between-Plano-convex-lens-and-biconvex-one



Now, according to their website, seems I don't want plano-convex:

"Plano-convex lenses, the most economical transmissive focusing elements available, are ideally suited for laser heat treating, welding, cutting, and infrared radiation collection where spot size or image quality is not critical."

--I'm kinda thinking for my needs, spot size and image quality IS critical! ;) Their description of meniscus's...
"Meniscus lenses are designed to minimize spherical aberration producing a minimum focal spot size for incoming collimated light."

Virtually all laser engraver lenses for sale on ebay are meniscus lenses-- and of all the plano convex lenses for sale on ebay, almost all were clear not yellow, and for totally different machines and/or purposes...

I did buy 3 ii-vi lenses off ebay yesterday, two 2"ers and a 2.5"er, so I'll be reporting back with results when they get here... :)

[Kev Williams]

https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2380057.m570.l1313.TR1.TRC0.A0.H0.Xlaser+ lenses.TRS0&_nkw=plano+convex+laser+engraver+lens&_sacat=0
^^^ this here is a link to what comes up when searching ebay for plano convex laser engraver lenses-- any that actually look like it would fit 'our' machines, is a meniscus ;)

https://www.ebay.com/sch/i.html?_from=R40&_trksid=m570.l1313&_nkw=laser+engraver+lens+meniscus&_sacat=0&LH_TitleDesc=0&_osacat=0&_odkw=plano+convex+laser+engraver+lens
^^^ and these are the meniscus offerings...

What am I missing?

[Scott Shepherd]

What am I missing?

A phone call to people who know more about lenses than all of us combined? :D

Ebay isn't my first choice for trained professional advice.

Plus, on that ebay link you listed as the first one, it says 0 results for what you searched so it's just showing you a search with some of those items missing.

For the record, I believe Gary is right. Here is the description of the lens that I ordered 5 years ago :

The fact that it says PO/CX leads me to believe it's a Plano/Convex lens.

ZNSE PO/CX LENS 0.75''DIA 2.0''FL AR/AR 1 ET=.080''

[Kev Williams]

Not trying to be argumentative, honest, but why is it every laser optics mfr's website I've found describes plano-convex and meniscus lenses exactly as ii-vi described them (as I posted above)? These descriptions lean toward high power cutting machines, but that shouldn't change the generalities...

Now, I've bought many a lens from China since I got the Triumph almost 5 years ago, and while many of them are described in the ads as meniscus, they are in fact plano-convex, as the bottoms are flat as a pancake. All the lenses in my 'good' machines are definitely plano convex too. But I DO have two actual meniscus lenses, they're a pair of GaAs 2" lenses I got a couple of years ago, the bottoms of these are most definitely curved. And, they're true focal length is closer to 1-3/4" than 2". They work nicely, but I've never done any actual spot-size experiments to compare them to my other lenses. I've used 3" and 1-1/2" Chinese lenses in my LS900 once or twice and they worked great, but I've never tried any of them on stainless. Haven't tried one of the GaAs lens in a good machine yet either. Could be one of these cheapies will make my LS100 do stainless better than its current lens. But of course, I can't just swap them because the stock lenses measure 18.8mm dia, and a 19.08 lens won't fit. The GCC lens may be 18.8 too but haven't measured it, I just know that it's smaller...

SO, I'll bet a buck the 'meniscus' lenses I ordered will likely be plano's.

That all said, since every lens I own 'cept the 2 GaAs lenses are plano's, I'd still like to know what's going on with the LS100 lens that it won't turn Cermark black?

[Scott Shepherd]

I'm just giving you a hard time Kev, because you keep asking questions and I keep saying that you can call them as ask them. I don't know the difference or why one works better than another. But I do know they were quite helpful and knowledgable.

Might be worth a call just to get educated. Just in case the rep doesn't know, I suspect they'll get you in touch with someone else who can.

[Kev Williams]

My tinnitus is getting so bad 9 out of 10 phone calls is mostly me saying 'sorry, what was that?'... And I can't understand ANYone who's on an iphone. They've got all the high tech stuff working well, maybe they can actually make the talk quality better than a soup can on a string?
( rant off ;) )

The simple reality is, I want/need a lens for the LS100 and Triumph that will make Cermark black!

[Gary Hair]

Did you look at this link Kev? Our lenses are flat on one side and curved on the other, right? Now which one is like that in the picture from this link.
https://www.quora.com/Whats-the-diff...d-biconvex-one (https://www.quora.com/Whats-the-difference-between-Plano-convex-lens-and-biconvex-one)



https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2380057.m570.l1313.TR1.TRC0.A0.H0.Xlaser+ lenses.TRS0&_nkw=plano+convex+laser+engraver+lens&_sacat=0
^^^ this here is a link to what comes up when searching ebay for plano convex laser engraver lenses-- any that actually look like it would fit 'our' machines, is a meniscus ;)

https://www.ebay.com/sch/i.html?_from=R40&_trksid=m570.l1313&_nkw=laser+engraver+lens+meniscus&_sacat=0&LH_TitleDesc=0&_osacat=0&_odkw=plano+convex+laser+engraver+lens
^^^ and these are the meniscus offerings...

What am I missing?

[Kev Williams]

So I decided to check my lens arsenal just to see...

Turns out my two 3"ers, and my two 4"ers are plano. And most of my 2"ers are actually meni's, even the one with 3 cracks. I have 2 new spares I got the same time as I got the GaAs lenses, they're both meni's.

My favorite lens at the moment in the Triumph is a 2-1/2", and it's a meni. So when I get some time I need to locate all the plano's and do some side by side. Because until I just now checked, I thought only my GaAs lenses were meni's. The concave on those is quite obvious, the others not so much.

Meniscus, notice the daylight-
395327

Plano, flat--
395326