Full problem with half focus -Help needed

Fri Feb 28, 2020

Hello,
I have a problem regarding good focus on parts of the bed. The weird thing is that I can not get a good focus closest to the laser tube, the further away the nozzle is the better result, the bed is 1300 x 900 mm.
Beam exits tube on left side (rear), I get worst results in the upper/rear left corner and absolute flawless results in opposite corner (front/lower right), there is not really a sharp edge where it flips, it gets gradually worse on the upper left half of the table (starting from the diagonal). It's as if the beam length is shorter than 1700 mm is becomes fuzzy.

Things that I have checked:

Beam path lies in a plane.
Bed is level in relation to beam path plane.
Lens is at same distance from material regardless of where on table.
Beam comes out from nozzle as a round dot all over the table (just bigger closer to the laser tube).
All optics are spotless clean.
Air assist is consistent all over table.

My biggest suspicion is the tube itself. After my original tube burned out I bought an SPT-laser tube with red dot aim diode, (Fantastic for calibration purposes, have not burn-targeted a singel piece of paper since). BUT after a handfull of days the water cooling hose loosened completely on the tube during operation leaking water. I contacted them and complained (many CAPS), and they strongly suggested I choose a more "standard" replacement tube without red dot because it was "still under development". I'm thinking that it might not only be the coolant hose issue that they had problems with. It could be that the coherence alignment is off or that the integrated prism for the aim laser is screwing something up. But if it was coherence it would become worse at longer distance.. yes? The prism would be consistently bad.
Tube used: https://www.sptlaser.net/co2-laser-tube/tr-series (130 W)

I've lived with this "feature" for almost a year now and managed to solve bed placement logistics so far but my commissions are getting bigger and I can not dodge this any longer. I'm clasping for straws here, I'm checking if the mirrors could affect some wavelength interference by not being circular polarized L/4 phase shift something something...
Many smart people have heard the problem and frowned their faces, wrinkled their foreheads and asked the same friggn question every time: "Are you sure? It should be the other way around!"

Is this forum my Obi wan?

Fri Feb 28, 2020

Your mirrors are not aligned correctly. Look at these FAQs and follow them religiously [if you are religious, other wise very closely]. The #2 mirror is not aligned correctly. I have a similar machine and the larger the bed, the harder it is to get it perfect. When a target on the #2 mirror beam is centered at the extreme rear as well as the front you will be a happy man. If it was easy... anyone could do it. Keep faith. Gene

Fri Feb 28, 2020

Henrik,

I'd love top hear more on that tube. I'm considering upgrading to the TR90. Russ has said that the SPT tubes are great quality, but you say you've had problems. I'm hoping it's just a combination of your bed size and the #2 mirror.

Please, expand on it more here, start a new thread, or PM me. Also, I see you have a rotary. What's your opinion of what you have / what do you like or dislike about it?

Sat Feb 29, 2020

Gene Uselman wrote: Fri Feb 28, 2020 Your mirrors are not aligned correctly. Look at these FAQs and follow them religiously [if you are religious, other wise very closely]. The #2 mirror is not aligned correctly. I have a similar machine and the larger the bed, the harder it is to get it perfect. When a target on the #2 mirror beam is centered at the extreme rear as well as the front you will be a happy man. If it was easy... anyone could do it. Keep faith. Gene

At the moment the machine is positioned at a bad location making it hard to get to 1st and 2nd mirror (will adress this next week), but it is possible to see that the dot does not move (within my perception range) when moving the 2nd mirror from rear to front. The dot moves ever so slightly when moving the 3rd mirror. In my experience any traveling target would result in the beam hitting the inside lip of the nozzle and create an oblong shape or even a crescent shape, that does not happen in this case, It just becomes bigger/diffuse. It can cut, the kerf just becomes bigger in both X and Y. If I overcompensate the other way the reverse result wold happen, worse at the other end, but that does not happen.
It could be that having the eyeball closer to the mirror would result in a better calibration, will try again and try to do better but I'm slightly skeptical that it is a misaligned mirror. BUT honestly I've tried som many things I could have forgotten/missed something super basic when fiddling with all screws back and forth.

To comment on Dave V request:
I actually removed the prism for cleaning once and found that when I put back it has... less than desirable tolerances, which means that the red dot and IR-beam can actually hit different places. So use only compressed (dry) air to clean this part AND se if you can enclose the beam between the tube and 1st mirror to minimize particulates getting on the tube optics. My stated problem remained after I corrected that flaw. Other than that and the hose coming loose I have no real problems (except maybe perhaps a faulty tube). I recommend the tube with the caveat: do not loosen the diode under any circumstances and check the coolant hose is properly attached. (they have probably fixed that by now).

Sat Feb 29, 2020

Just a simple little reminder; adjustment and alignment CAN NOT always be done with just tweaking a screw here and there.
To properly align everything means sometimes you have to modify the original build.
Things are not always as square or parallel as you may think.
Properly checking EVERYTHING is very important if you want a laser that works correctly and to its maximum ability.
I bought my Chinese laser to save A LOT of money, but the Chinese guy that built it did not care how good it worked, only that he got paid to throw it together.
My first laser worked pretty good out of the box so I did pretty well with it. However, when it caught on fire and I ordered the second one, it was an identical laser as the first one and it was junk. I had to modify the bracket for the 2nd mirror, square the gantry to the rails, modify the laser head bracket to get it square and level the bed. Oh, and it all had to begin with squaring the tube first. The gantry was so far out of square that I had to remove it completely to drill and slot new holes in the slides to fix it.
My 2nd laser now runs circles around what I was able to do with the first one.
I won't go into the procedures to check all of this because Russ has some really good videos that will walk you through it.
In summary, you do not have to check all of these things if you trust the guy that built it, which is what I did with my first laser.

Sat Feb 29, 2020

This is a Bodor laser which I consider well designed and assembled... not to say that any problem is not possible and you will do well to verify all the things that Willy mentioned. You have a serious machine there and it should work very well when sorted out.

Sat Feb 29, 2020

Here here. I'm seven months in and still working on it. The truly bad part on my unit was a cooling and flow switch problem that cooked the tube. Dollar wise I have not had to put a lot into it and the manufacturer is replacing the tube. but time wise...

Conservative estimate is a full day when added up, realistically more like two with all the little stuff. Add in all the mis-cut projects and general frustration and I'm probably well over a month of troubles. Bad Chinglish emails only add to it.

Sun Mar 01, 2020

Yes, it is a Bodor laser, designed in Switzerland no less (!!), has a sturdy frame out of big square steel tubing... but still put together in China. I did not recall I had this issue with the original tube, but then it stood on a much flatter floor, it could have set slightly.
BUT still, if the beam path is confined to a plane it should not matter. If the laser hits the same spot on the mirror at both ends of the linear rail it is straight, even the Chinese can not make bad light that bends in air :p.
I put an indicator clock in the head and moved that around the bed and was within reasonable tolerances for the extruded aluminum profiles the table is made of, around +/-1 mm at worst. I use a 5 inch lens (127 mm focal length). The focus depth is bigger than the measured tolerance measurement.
I'm going to do a tear-down tomorrow and start from scratch.

And I can relate to your situation Dave, no real understanding of what a unscheduled stop in a production machine implies from the tube manufacturer. Their firs line of customer support has their script that they use and not until you comply with their rudimentary checklist (by sending video of the machine) can you be directed to more "senior" support. They offered to give me a new tube if I payed for shipment, cost slightly more than the tube itself.

Sun Mar 01, 2020

Yeah, Russ said for one of his the shipping practically doubled the cost.

I'm 'glad' to hear that your problem with the red dot happened after you removed it for cleaning. I seem to recall someone else with a problem with them but it was after something similar as well, so it will get dusted and cleaned in place, no removal. I did another search last night when I should have been in bed, and I 'think' I have found a distributor in the US. If their web site is to be believed they have flat rate $5 shipping and will ship immediately on COD.

So far I have found two options with Cloudray. Pay full price with outrageous but snails pace shipping on the web site via PayPal, or talk ( email ) directly with the sales department, get a better price and 3-5 day shipping... but have to pay with a bank transfer. $50 in my case.

When I ordered my new controller, I saved $10 but three weeks shipping time. If I order the SPT TR90 from them it will be about $55 savings. If this US company is to be believed, I will save over $100. Ruka Laser https://ruka.world/ They don't seem to have quite the diverse product line as Cloudray, but that may just be what's on the web site, I have not talked ( emailed ) directly with them yet. They show offices in the US, Mexico, and Chile.

Sun Mar 08, 2020

UPDATE

The machine has moved to a more flat/stable section of the floor and after some tweaking I get consistent good results across the entire bed except the inner most upper left corner about 30x30 cm triangle. Same as before but much smaller area.
SO, I guess it was an alignment issue after all... Still don't get how it can exit the nozzle as a bigger round spot.
The size difference from good results and bad is 0.3-0.5 mm diameter to almost 1,5 in diameter. The distance difference from lens to work surface between the good and bad areas is about 1 mm, with a focal length of 127 mm that should not be an issue.

Good enough to continue to work anyways, I'll tinker away with more delicate adjustments during off-hours.
Huge thanks for the feedback from you all!