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Allan Longson
02-19-2014, 5:24 AM
We have a 50W ULS6.60. Recently it has been struggling to cut 4mm venered wood. We have checked the alignment, we clean the mirrors and lens religiously but results have just been getting worse even though we keep bumping the power up and dropping the speed. On the last job today, I was looking into the machine whilst it was cutting and noticed a halo of light on the wood that is lens shaped and the laser dot is about 1.5mm off from the center of this halo. Looking at the alignment beam, the dot appears to be center of the lens so the question I have is is this halo and the position of the laser beam in it a reliable guide to finding the center of the lens?

Mike Null
02-19-2014, 5:39 AM
That would appear to be an issue with the mirror or the lens or a focus issue. I haven't seen it before. Is it possible to install the lens upside down?

Dan Hintz
02-19-2014, 6:16 AM
Check the output window on your tube... halos typically mean one of two things: a lens has shifted off axis (the cartridge lens is impossible to fix by the user, the focusing lens is much easier), or a mirror is aiming the beam well off-center of the lens.

Allan Longson
02-19-2014, 6:33 AM
That would appear to be an issue with the mirror or the lens or a focus issue. I haven't seen it before. Is it possible to install the lens upside down?

You can install it both ways but we put the replacement in the same orientation as the original one (from new). Unless Universal installed it incorrectly then we assume it is in the right way.

Allan Longson
02-19-2014, 6:41 AM
Thanks, we will take it apart tomorrow and have a good ferret around to see what is wrong.

Mark E Wilson
02-19-2014, 10:09 PM
Allen I had a similar issue with my Universal. We figured out the laser was hitting the side of the air assist cone. After cleaning everything and checking everything ad pulling all of my hair out I was re-cleaning the mirror above the lens and discovered it was loose. I added a little epoxy and it seems to be working fine. I would call ULS though, they are always super helpful and can send instructions for just about anything.

Allan Longson
03-01-2014, 3:23 AM
An update on this and looking for advice on what to do next.
As I said in the original post, over time we have had to bump up power and drop speed to cut the same wood. Some days things work perfectly, other days we get lots of rejects because things just don't quite cut through. It's on the horizontal cuts we have the problem, mainly top and bottom of the work sheet. Vertical cuts are ok all over the job.
In the last 2 weeks we have: put in a new cartridge, lens and end mirror. The cartridge made no difference, the lens and the mirror a little. We are also going to replace the 1st mirror as we see some marks on this. The lens we are using we sourced from China, our local ULS agent reckons his oem lens (at 10x the price, US$450) is far superior.
After all the changes we still have the halo, and it was even more pronounced when we put the new cartridge in. However the laser beam is now center of the halo so I suppose that is a step forward.
Also we don't use an air assist cone.
Can the lens make that much of a difference? If so, can anyone recommend somewhere where we can buy quality lenses?
Could it, after all this, be the power supply slowly giving up over many many months?
We are now scratching our heads wondering what else we can try to get the cutting capabilty of the machine back to where it was when we first purchased it.

Dan Hintz
03-01-2014, 1:17 PM
Even the $30 lenses from eBay are just as good (in these machines) as the "high-end" ones pushed by the big companies (lenses are a very high-profit item for them... no appreciable warehouse space necessary, cheap to purchase).

I can't think of a reason for a power supply to create a consistent halo (off the top of my head), but that doesn't mean one doesn't exist. Still, an optics issue is the most likely cause by a significant margin.

Mike Null
03-02-2014, 6:17 AM
Even the $30 lenses from eBay are just as good (in these machines) as the "high-end" ones pushed by the big companies


I seriously doubt that.

Scott Shepherd
03-02-2014, 9:20 AM
I have to agree with Mike on that. I got to know our old ULS rep pretty well and we'd talk for hours some times about issues, the trade, etc. I recall talking to him one day after he'd spent most of day trying to solve a customers issue. He told me at the end of the day, he swapped out the lens with a spare he had brought and the problem went away. He asked the customer where he got the lens he was using and the customer told him he bought it off of ebay.

So they chased the problem for hours, measuring power, aligning things, measuring the power supplies, etc, all for the issue being the lens.

I'm not saying that's your issue, but I'd certainly try it, especially if you had access to one to try for free.

Dave Sheldrake
03-02-2014, 9:34 AM
ULS lens's are made in the II-VI factory in China :) A good lens can make a difference over a bad one but not by huge factors. Cheap ($10) lens's from China are usually pretty poor but once you get into the $30+ range they are all pretty much the same thing.

cheers

Dave

Scott Shepherd
03-02-2014, 10:08 AM
From a trouble shooting standpoint, I think you have to try the lens. You've replaced the tube, so it's not that. If it's not the tube, there's not much left between the tube and the workpiece, other than lenses and mirrors. If you aren't using what they require, I suspect that's your issue, not to mention it pretty much stops much tech support. Not because they won't help you, but because you're not using their products so they can't do much other than to say "The tube is good, the other parts you bought are aftermarket and we have no way of verifying those, so we're not sure how to help you proceed".

It almost has to be lens and mirror issues. If it's aligned and cutting incorrect, there's just nothing else it could be, I don't think.

Scott Shepherd
03-02-2014, 12:23 PM
I think they are the same "in theory", but from what I was told from someone in the business I trust, is that it does make a difference, and I believe that.

I'm open to suggestions on what else it could be, if the beam is good, the alignment is good, and the problem exists, what else can it be? I'm sure it's possible it's something else, but the one variable is that they have used after market mirrors and lenses.

Dave Sheldrake
03-02-2014, 3:32 PM
I've been to the II-VI manufacturing facility in China if that helps? there are lines and lines of processes with different manufacturer destinations in the control bins. The only separating system used is the focal lengths (most western stuff is metric vs most Chinese stuff is imperial) there are very few places in the world that actually grow the Zinc Selenide used so there's a good chance no matter who is selling them they all come from about 6 different companies. Chinese manufacturers get big big price breaks on their stocks so Chinese laser builders/assemblers get the lens's at a much lower price (not forgetting they order 1000's at a time)

cheers

Dave

Scott Shepherd
03-02-2014, 4:03 PM
I've been to the II-VI manufacturing facility in China if that helps? there are lines and lines of processes with different manufacturer destinations in the control bins. The only separating system used is the focal lengths (most western stuff is metric vs most Chinese stuff is imperial) there are very few places in the world that actually grow the Zinc Selenide used so there's a good chance no matter who is selling them they all come from about 6 different companies. Chinese manufacturers get big big price breaks on their stocks so Chinese laser builders/assemblers get the lens's at a much lower price (not forgetting they order 1000's at a time)

cheers

Dave

I don't think the location of the manufacturing is at question. Most every high tech gadget in the world is produced in China. Then again, so is just about everything in the dollar store. That doesn't prove anything other than they are able to produce VERY high quality products as well as complete junk.

Without knowing the source of the optics in question, this is all speculation. No one yet has come up with any other theories on what's going on with the OP's issue. My theory is it's his optics. What's you and Dan's theory on what's causing this?

Allan Longson
03-02-2014, 5:12 PM
Thinking about how to measure the output of a laser at the surface. What if you had a container with a measured amount of water at a specific temperature (start temp, say 4 degrees) and then at a x power level and x speed and x ppi you timed how long it took for the water to reach an end temp (eg boiling)?

Dumb idea or not?

Notwithstanding an optical issue of some sort, I still can't think of any reason why horizontal lines in our work often don't cut through yet all the vertical lines will?

ps - the mirrors we replaced are oem, ouch on the bank balance....

Dave Sheldrake
03-02-2014, 5:49 PM
A halo effect is caused by scattering (usually backscatter) but I'm not quite sure where it's going to be rooted. The total reflector may have a fault but this kind of thing is more usually alignment. Halo's ON a lens are usually lens damage (the coating has been overheated) but as the lens has been changed having the same issue with two consecutive lens's is highly unlikely. It may still be an optical abberation but if it is then it's going to be in the resonator optics.

Hummmm how did you adjust the focus Alan? Chinese lens are rarely what they say on the box, focal position can be up or down a mm or so.

cheers

Dave

ps: Alan, calorimeters aren't a good way to check beam power, too many losses to be accurate unless they are properly insulated.

David Somers
03-02-2014, 6:03 PM
Dave,

What instrument or method do you prefer for checking beam power?

Dave

Mike Null
03-02-2014, 6:06 PM
Alan

I believe you can borrow a meter from Universal--at least they used to do that.

Scott Shepherd
03-02-2014, 6:26 PM
A halo effect is caused by scattering (usually backscatter) but I'm not quite sure where it's going to be rooted. The total reflector may have a fault but this kind of thing is more usually alignment. Halo's ON a lens are usually lens damage (the coating has been overheated) but as the lens has been changed having the same issue with two consecutive lens's is highly unlikely. It may still be an optical abberation but if it is then it's going to be in the resonator optics.

Can't be in the resonator side of the optics, he just replaced the entire tube, which has all those optics built into it. Also highly unlikely that 2 different tubes have the same bad optics from the factory.

I am assuming the tube is fine, since it's new. I'm assuming it's also lined up properly. If so, it has to be the lens. There's no other piece of the puzzle. That's my opinion. Could be completely wrong, but there's just not that many pieces in the chain.

Dan Hintz
03-02-2014, 7:53 PM
Place the focusing lens directly in front of the laser's output window (just hold it by hand at the approximate appropriate distance), and see what kind of a pattern you get. If the pattern is clear, that narrows it down to the mirrors. If not, that narrows it to the internal optics or the focusing lens. Let's start there.

Kev Williams
03-02-2014, 9:23 PM
Mirrors-- the mirror above the lens in my LS900 is held in place with a snap ring. I removed it once to check it out. To look at it, it's identical on both sides. I thought "what a good idea, if the first side goes bad just turn it around!"

Nope. I did turn it around and tried it, it wouldn't engrave squat. I could barely cut paper with the thing. Changed it back around and all was well again...

I could see absolutely NO difference between the two sides. But obviously there is! From that test I can see where even a tiny issue with a mirror could have big effect on the beam...

Dave Sheldrake
03-03-2014, 3:23 AM
I'm still thinking alignment Scotty, Halo's are caused by scatter but it's working out what is causing it.

Kev's right, mirrors can cause huge problems so that's a possibility.

Could be the PSU I guess but not quite sure how to test that. I'd go with Dan's suggestion, rule out the mirrors and tube then go from there.

cheers

Dave

ps: Dave I have a power meter and beam profiler.

Allan Longson
03-03-2014, 4:33 AM
Not sure how one would check the laser beam before the mirrors unless we bypass the lid switches?

walter hofmann
03-03-2014, 5:06 AM
hi there
just my two cent from experience because I had sometime a halo too and was going crazy then I found out that the laser head did change in plump good knows why and after align the head in perfect plump and level the halo was gone.
maybe that's the reason here too.
greetings
waltfl

Dan Hintz
03-03-2014, 7:04 AM
Not sure how one would check the laser beam before the mirrors unless we bypass the lid switches?

I'd remove the laser from it's mount for ease of access. Set it on top of the machine, make a simple cardboard box extension to put the focal lens at about the correct distance from the cartridge, and do a test fire. Obviously pay close attention to what you're doing and avert your eyes during the test fire.

It will take you probably 30 minutes to set all of this up, but it wall answer a lot of questions at once.