TLDR: A combination of alignment problems and wrong selection of lenses has resulted in premature burn out.
The failed lens was examined and appeared too clean to be caused by debris buildup. Significant deviation from center of the burn mark indicated misalignment. Pictures were taken scaled based on the residue/markings left by clamping in the tube. It was evident that the misalignments were substantially severe enough to reduce power delivery.
When the power drops, users compensate by bumping the %power. This leads to the second issue of the incorrect lenses used only being rated for 80W. This will be fine up to 60% power (out of 130W) but when bumped up to compensate for misalignment will lead to sudden failure.
Slightly edited the first figure here since the red circle I was using for scaling kind of made it hard to see where the lens actually is in the assembly.
For alignment I propose that we make a “laser lollipop.” I’ve always just estimated it by eye using with a corner of a piece of paper. But we could inform users that if its outside the circle then a ticket needs to be opened as part of the basic laser training.
Edit: The tip opening on the nozzle does indeed appear to be 2mm on this set. The banged up head also appears to have a 2mm opening. The larger the opening the less sensitive it will be to alignment but more sensitive to debris.
Edit 2: Maybe I was handed 1.) a 2" lens with the 2mm nozzle 2.) a well used 2mm nozzle 3.) a new 2" lens 4.) a broken 2" lens and I confused this to mean these were all parts that were used together.
Edit 3: I’ve checked online and Thunder sells the 2" lens assembly with a 2mm nozzle standard. Have we been buying 6mm nozzles and replacing them?
Head Assembly: 2" Head - Nova – Thunder Laser USA)
I think the general recommendation still stands but maybe the operating procedure should only call for a mandatory alignment check when a 2mm nozzle is used. Making sure all lenses have the correct rating for the output power will also be helpful.
Again chiming in with old data, we used to order the Cloudray II-VI lenses (that’s what’s linked on the old laser wiki page). They would still fail more frequently than seemed reasonable, but maybe the frequency has increased in the past few years.
We also made a point to use the larger openings to avoid clipping due to alignment errors. Obviously this is a bandaid solution to poor alignment, but the thunders are relatively large machines and not as mechanically stable as the higher end lasers, so alignment is especially difficult to maintain.
A good maintenance program, both with careful and precise alignment, and good maintenance of the linear rails and chassis, would be a great step to actually solving the alignment woes.
Being able to use the smaller opening should increase the velocity of the air assist which would help direct smoke away from the cut. It would be a step in the right direction.
A few months back I’d gotten a sample of stickers that were in an alignment target for use when aligning. I quite liked them but had only ordered a pack of like 10 to see if they would work first . They also make a bunch of other tools (of various quality) to help align - Like laser sights that screw into the head unit to make it easier to trace the path back.
Thunder had donated us a good dozen lenses and mirrors of their brand almost a year ago back now. As of around 2 months ago, we only had replaced one lens since then so there should be a bunch of the nice ones laying around in the maintenance cabinet still.
Seems like we should make sure lasers are centered so we could use a small tip. When HB showed me a lens earlier this week it looked like it had black soot on it.
So either the laser is burning the lens or air velocity flooding the nozzle is not keeping smoke and debris from the part out of the nozzle.
We definately needs lenses rated for higher power than our lasers can output.
Also as a note, and I don’t know which side this burn was on. In the past we have had super sooty material go in through the top side of the head unit and land on the top of the lens, where it caked on and burned. Not tons we can do about this since there is an airflow on that side of the lens… Usually it’s why we just warn people to try to use a lower power and more passes so that they aren’t creating as much instant soot.
(As an amendment, I was only ever using the higher powered lenses/ the lens itself was not the degrading factor when I was handling maintenance)
This was on the bottom side but I did not notice much evidence of caked on debris when examining the rest of the surface under the microscope. Outside of the burn zone, the lens looked relatively good.
Also please note that some of the particles that may have been observed during cleaning will likely also be a result of the ZnSe being vaporized by the heat. This is very toxic selenium dioxide powder so I’d recommend gloves if the ZnSe windows looks burned.
Those were old lenes. No way of knowing which laser they came out off… the alignment has been dialed in and currently in the center of rhe 2mm hole:.
It has come to my attention that we have members lowering and raising the bed to set the focus. They are setting the focus pad under the head and raising the bed until it makes contact.
When asked they say that’s how they were trained,.
We will need to correct this training. it’s not good for the bed to crash into the lens tube. Also we have a member or members changing the Jog speed from 150 mm to 500mm. This isn’t good for the alignment either especially when the head is crashed into projects…
As for alignment you’re all talking like this is as easy as adjusting a tie rod a quarter to to center the steering wheel. It easy once you know how, but it’s a skill they will have to learn. There is a learning curve.
I have more we can discuss in the committee meeting which is in the morning. Then we clean and Tweek the machines…
from what I’ve seen in the main cause of lens failures is a dirty lens. Thunder recommends the lens cleaned once a day minimum however with heavy use, they say every 30 minutes.
Coming in should check the lens prior to using the machine to make sure it’s clean. If they’re cutting something that is creating A lot of soot. They should be neighborly Clean the lens for the next User.
Those were old lenes. No way of knowing which laser they came out of… the alignment has been dialed in and currently in the center of rhe 2mm hole:.
The lens that has the small spot is from donner pulled by @gh05t on Wed. The other one is old as you mentioned and has been used as an example. I observed evidence of substantial misalignment on both. I just wanted to bring up the fact that perhaps the alignment does get knocked off by enough to render it incompatible with 2mm nozzles and that some of the lenses at least may not be rated for the power output.
With the exception of the nozzles on the lasers currently, all of the nozzles appear to be 2mm. I think when I counted today there were 8 of the 2mm nozzles in the box since the head assembly comes with 2mm as standard apparently.
I know its only a sample size of 2 but both had alignment issues that would not be compatible with 2mm nozzles. I agree that there are a number of different corrective measures that could make improvements. Obviously which things will yield the most benefit should be determined by the laser committee. Hopefully my bringing this to y’alls attention was useful in some way.
Edit 2: Sorry I just tend to be full of suggestions and feel free to ignore any that seem unhelpful. I do have another one though and I can’t resist sharing. Perhaps it would be good to take a picture of each failure in the future before attempting to clean it so as to gather more data as to what are the biggest problems. Edit 3: Tend to bungle posts when on mobile so reorganized it a bit to make it clearer to read
I was proposing a quick check type thing rather than having people fire the actual CO2 beam through tape at different head locations. Perhaps people could just do a simple “lollipop” test using the red indicator laser dot. Its not a substitute for full alignment checking but its quick and easy and in my experience severe crashes will throw off the red laser indicator as well (at least on the universal laser I used to be responsible for maintaining).
Will not suddenly make a regular user a maintainer but might give enough of an indication to avoid running it when its in a very bad state after a big crash.
I would love to attend Laser’s meeting tomorrow but unfortunately I don’t think I can make it. Which is one of the reasons I decided to just post this thread.
Haven’t cut with the laser yet but hope to some time in August. What do you all think about adding a link to a relevant manual or video in this thread so I can learn about what procedure to follow, to not contribute to this problem?
We have specific training regarding the lens cleaning. This isn’t a user serviceable item. Please feel free to get involved and join the maintenance program.
