Back to trying to 'figure out' my laser power vs distance

I posted a question here recently about how much ‘power’ should be lost vs the distance traveled. That is - the power is reflected through 3 mirrors and ranges in distance from <12" (top left corner; min x/min y) to probably approaching 48" (bottom right corner; max x/max y). I had been using painter’s tape to try and align the mirrors and it was suggested that I should use ‘watercolor paper’ and cut out targets instead.

I removed the mirrors ostensibly to replace, but in yet another post - determined that I have the best quality mirrors already (polished metal?). So I merely cleaned them and reinstalled.

I am STILL struggling to try and get any kind of ‘cutting power’ when I work in the max x/max y area and one post suggested that my laser may be deteriorating (same post where I think I got the watercolor paper suggestion… sorry - sometimes the information ‘sticks’ in my brain, but the source disappears).

I cut out a bunch of watercolor paper targets and then started testing the alignment/power sequentially with NO mirror adjustments. Attached is an image of all my results with comments. Remembering that my reference is ‘top left’ is min x/min y (least traveled light distance) - I am looking for input/opinions on what I may be seeing/encountering. Personally - I THINK mirror alignment is reasonable… I wonder about the ‘shape’ of the beam that seems to be odd on a couple of the targets. Remembering that I am manually pushing the pulse button on my Ruida controller - there is some definite inconsistency in how long each ‘pulse’ would be. If someone can suggest a method to create a consistent pulse length and power - I would be open.

Thanks again in advance… this forum has yet to let me down!!


DANG it! Forgot to include the pic on the original post… sorry about that folks :frowning:


For Ruida controllers, you can set a pulse duration by digging into the Menu → Laser settings.

For GRBL controllers, I think you could hand-hew a G-Code file to turn the laser on, pause for a while (with G4 Pxxx where xxx is either seconds or milliseconds or something, depending on your controller), then turn the laser off again. You’d send that file to the controller every time you want a pulse.

With that said, I think all your targets show a defunct laser tube that is not operating in TEM00 mode. At the entry to the first mirror, the beam should produce a nice circular disk, maybe 3 mm in diameter depending on the power & duration, not the tiny spot you have.

The C shaped spots are completely wrong, no matter where they occur.

Given enough travel distance, the crappy beam spreads enough to look almost normal, but that ain’t normal.

Other folks will surely chime in with different information, but IMO the reason your laser doesn’t cut properly is due to a bad tube.

You need to tell us what kind of laser you have… the one in your profile seems like non-sense.

IMHO, this pursuit is a waste of time.

You simply have no control over this, so is it academic?

Looking at your targets (up is up in position?) You have more serious issues than the path loss to get this working.

Your TEM0 state appears to not exist, so it will never work correctly.

You impede our ability to help you with no information about your laser. So help us out.

@ednisley has given you the bad news… probably true… I bought my last tube from Cloud Ray…


I apologize for the lack of information - it wasn’t me being difficult… it was me being ignorant of requirements.

I have a red/black chinese CO2 laser that is supposed to be 100W output. Based on my tube measurements (length x diameter) it would appear to be correctly rated. There is no max current rating on the tube itself and there is some manufacturer info on the side of the box but I don’t think that will lead to anything of value. The previous owner put in a current meter, added a camera (which I have yet to hook up) and added a red dot (which… needs adjustment). And yes - the ‘tab’ on the targets is ‘up’ (as best as I could do it manually).

I’m not prepared to replace the tube at this time - only because I don’t really do anything particularly ‘big’ (I’m not really using the max x/max y area), and I’m certainly not doing anything that is financially productive. Considering when I was reviewing the machine before purchase - the previous owner was able to cut through a 3/4" pine board I provided in 3 passes. Somehow I think that something happened in the move. I’m going to look into adjusting the pulse length/power and I’m going to research the ‘TEMxx’ information. I think I MAY consider adding an ‘hour meter’ to my tube if/when I end up replacing it.

One thing I have yet to do is run any kind of consistent material tests… I’ve been too much of an excited kid with a ‘chemistry set’ trying to make ‘smoke’. I think all of my immediate projects/plans are complete - I can settle in and start methodically testing and evaluating.

Thanks to both Ed and Jack for the quick and helpful responses. I really appreciate your experience and knowledge and look forward to learning more from you both and this whole forum as I learn more about this laser I have.


The tube may measure properly … many good tubes manufacturers produce grade B tubes. They don’t sell them to the good customers of theirs, but to the vendors building these machines at low cost. A grade B 100W tube may produce 90/95W instead of the correct power output for the current draw. This is generally attributed to mirror alignment during manufacture. These have to be very precisely aligned.

A grade B tube, they tell me, has it’s gasses degrade quicker because they have an incomplete lase operation…

How would you propose to accomplish this?

To be useful you’d have to monitor the L-On output from the laser and if there was a current draw for all practical purposes. The Ruida has this timing information, but no one has figured out how to reset them after you replace the tube :face_with_spiral_eyes:

It’s like a light bulb, it will burn out… I understand…

I would like to point out that I used my tube as it was going south. Once I discovered that it was failing, all limits were removed… So I ran it hard during it last week.

The drawback is the beam moved around and the next day I’d have to re aling it again. I can do that in a few minutes with the system I have, but most take 20 minutes or more. It quickly becomes counter productive.

If you TEM state is bad, it’s history and you might be better off parking it than using it.

Good luck


Again - one short response and my knowledge increases yet again… “The drawback is the beam moved around” was an ‘ah ha’ moment.

I think I saw a previous comment in these forums about the TEM state - and there is no post-manufacture adjustment that can be made for this. Is there a way to understand what ‘state’ it is? or is that just evaluation of the burn pattern on the paper as I have?

I believe you also stated that you purchased a replacement from Cloudray… I looked at their replacement tubes and from a China warehouse, they aren’t ‘break the bank’ expensive. And what is a ‘RECI’ tube vs anything/everything else? Is the $300 Cloudray $100W tube a worthwhile purchase? for a hobbyist like me?

As an electronics engineer - the challenge of adding an hour meter could be ‘fun’ (in retirement - ‘fun’ is the only driving force as far as I’m concerned… well fun, safety and necessity). And if I were even SLIGHTLY successful - I may be able to share the results with this group and actually provide a value instead of just being a knowledge drain…


So it was defunct when you got it.

My alleged 60 W CO₂ laser cuts ¾ inch pine in one pass at 70% power = mid-30s W, moving 2 mm/s. A 100 W laser should cut pine like (rather smoky) butter, assuming the seller knew its capabilities and ran it at a reasonable power for the task.

Here’s my problem: you’re a new laser user (as we all were at one time!) and, as you try new processes, you will ask The Forum for help. Every [obscene gerund] time, we will go through a tedious debugging process to rediscover you’re using a defective tube that cannot produce the results you expect.

It is entirely your prerogative to keep using a bad tube, but IMO you’re pretty much on your own, because ain’t nobody got the time to help you re-re-rediscover your laser has a bad tube.

Fair enough?

That feeling just never goes away! :grin:

I think you can if your a physicist :crazy_face:

I think it has to do with both mirror alignment within the tube and effects on the gas mixtures within the tube that you depend on working in a certain way.

A great tube will go bad sitting on the shelf, it will also go bad when driven with too much current, too warm and I’ve been told by low power levels. Most recommend a certain power level during the lase operation. If you check out a lot of the tubes, they will specify a minimum/maximum power output.

One had a 180W as a minimum of 36W meaning it wasn’t meant to operate below 20% power.

My 50W machine from OMTech turned out to be about 44W (Mahoney meter). I replaced it with a 40W from Cloud Ray and it produces 40W as specified…

These low cost vendors are where the grade B tubes show up… Just buy from a good vendor.


Ed - I hope your obscene gerund was not an indication of anger directly at me. I always attempt to come to this forum respectful of the knowledge base it contains and the time of the users involved. Until now, I was unaware of the tube state and was working in that lack of knowledge context. You and Jack have revealed good technical detail on tube quality and potential issues. Knowing that my tube is compromised, and running my test patterns (currently underway behind me) there will be no need to ask those questions. I will stick to ‘how to’ questions as it applies to Lightburn and possibly some direct laser ‘tips and tricks’.

Thanks for your help… now and anticipated in the future.


(edit: it was ‘gerunds’ that drove me out of teaching ESL locally… I couldn’t for the LIFE of me figure out why teaching non-English speaking people who only want to converse with their English-speaking neighbors and friends would care about ‘gerunds’ or ‘verb infinitives’. They just want to communicate better - not write 3rd year college papers.)

You’re fine… Knowing @ednisley it was in jest…

You have questions ask, none of us learned this by osmosis.

I know electronics hard/software OK, but didn’t know much about lasers until I decided to purchase on… now I’m a full on addict… :crazy_face:

Hang in there, you’ll get the hang of it… besides someones got to replace us when we old and expire…


Definitely not!

I do get frustrated when somebody (not you) asks for help in a rather aggressive sort of way, refuses to follow any instructions to provide necessary debugging information, then gets angry when the problem fails to resolve. You can identify those discussions by my absence. :man_shrugging:

So I could see your laser provoking an endless series of such interactions, because everybody around here wants to help and nobody starts by assuming the tube is trash.

Keep in mind that your laser can’t produce good results, so asking how to get better results won’t be a productive use of anyone’s time.

Other than that, welcome to an engrossing series of projects!

My esteemed wife taught ESL for a few years and, yeah, she had to ditch the text and get conversational.

As a wise man once said, English doesn’t just borrow words from other languages, it drags them into the alley and empties their pockets. English seems less a language than a collection of useful parts, to the extent that two of Mary’s ESL students could “converse” only in English and written Chinese. A wonder to behold!