Settings to "calibrate" power percentages?

Is it possible to have a “max power” setting somewhere in options to reflect the maximum percentage power the machine can output?

For example, I have a higher rated power supply than my tube can handle (42% power gives me 20-21mA) and I’ve set the limit in the DSP so it can’t go over 42%

Right now in Lightburn, if I set power to anywhere from 43% to 100%, the DSP just limits it to 42%.

Would it be possible to add a parameter in the settings to say “Max power is 42%” so when in cut settings, if you set something to cut at 100%, it sends 42%, if you set it to 50%, it sends 21%, etc.

A more advanced way of implementing this could be to say “at 30%, tube power is 15mA, at 42% tube power is 21mA. I have a 60w Tube” in order to try and “standardize” the percentages we’re working with

Of course, the math isn’t hard to do on your own, but if my machine’s “100%” from the perspective of the tube is instead “42%” from the perspective of the DSP, and your machine’s “100%” is “75%” at the DSP, sharing a lbm file would have vastly different results between different machines. If we could have a way of compensating and calibrating output power in software, the layer power numbers and material library numbers could stay (mostly) the same between machines (of similar power), cut/engraving parameters could be shared more easily, and .lbm files could require a lot less trial and error when shared.

It would be pretty trivial to add a scale factor for the power numbers, and I see no harm in it.

Doing anything to try to standardize across different power machines would be mostly futile though. My 40w laser will fire at 2% power. My 100w doesn’t fire until 11.5% because it takes more juice to make it ionize. There’s no way to do “delicate” work with that machine because the firing threshold is so high.

I keep seeing this idea come up here and in the FB laser groups. The thing people don’t realize is that each laser system would have to be calibrated to a standard reference. That is doable of course, but it would cost more than anyone is willing to pay and would require support in the various controller’s firmware.

Yeah it’s a nice idea that falls apart when confronted with reality. :slight_smile:

It would be more feasible with RF excited tubes, as their response curves are much more linear, and they’ll fire down to basically 0 percent.

There’s going to be some variation in standards, and for “exact” calibration, you’d have to have a starndard reference, but if you had some parameters to enter in, and some math, you could get within the ballpark rather than shooting from the hip.

With the wide variety of power supply/tube/DSP pairings out there, your mileage may generally vary, but on similar tubes, 15mA is going to give you similar power.

Since tube power is pretty much a product of tube size (and given that the machine manufacturers often quote ‘optimistic’ numbers for power), using that as a reference may give better accuracy as well.

As you’ve pointed out, this wouldn’t work well for machines of disparate power, but if even if our machines are different in bed size, manufacturer, colour, DSP model, etc but both have a 55x1200mm tube, 15mA on the meter is going to do roughly the same thing, even if my AWC DSP tells my LPSU to feed my tube 30% power, and your Ruida DSP tells your machine to feed your tube 80%. They’ll both read 15mA on the dial, and the actual power should be reasonably similar (taking into account minor variations by different manufacturer, and tube age)

While it’d be nice to have a “standard” percentage across different tube powers, that’s beyond the scope of what I was thinking. This would basically let people say “I cut material X on a 1400x80mm laser at 70% 40mm/s” and other people with a 1400x80mm tube would have a better place to start.

There are also shared material library possibilities as well. Library entries could be tagged with tube size, and filtered by such when it comes to sharing lightburn files. If a material type is assigned to a layer, and someone with a 1400x80mm tube shares it with a 1200x55mm tube, the recipient with the weaker machine could have lightburn automatically adjust the feeds and speeds to suit their machine based on the materials assigned to each layer.

This all makes sense to me, inside my own head, but I could be way off the mark. What are your thoughts?

You have contradicted yourself. Which is it? This won’t work for machines of disparate power or it will?

I understand what you want but without calibration, such settings libraries will only be a starting point. You would still have to adjust the settings to match your machine.

However, note that a good chunk of LightBurn users are people with diode lasers, smalller 40w co2 machines, and a whole gambit of everything in betweeen those and yours.

Yes, a number of people might have your particular tube size/ laser apparatus of similar power, but the vast majority don’t.

All it takes is for one noob to want “a library” to hit the ground running with, take the library for a diode laser, and use it on their 100w co2.

I foresee huge liability concerns, which is why there are no starting points provided with LB.


Definitely. There are just too many variables to try to use relative offsets rather than actual standards-based, calibrated power output.

If a user wants to get material/ job settings from others in the form of “power 20, speed 60” then they should get an epilog.

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Also, just because you mentioned standards:

Probably my favorite XKCD.

I refer to it often.

For this laser power library shall we use ISO, NIST, ASTM, ASME…

Clinton, I’m not saying the scheme you describe can’t work, just that it will take more effort and know-how than you realize. And, for the liability reasons Ray mentions, I don’t see it being added to light burn.

That doesn’t stop folks from exchanging material libraries amongst themselves.

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I think we’re on the same page here – I think that a “master” materials library would be an absolute disaster, since nothing is created equal here. My thought was a way to link the same material to different optimized cut settings for a different machine, if they exist.

For example, if I had a file I’ve created to be cut in 3mm acrylic, I’d have the option to set the “layer material” property to “3mm acrylic,” which would pull my own optimized settings for my machine from my own material library that I’ve dialed in. However, if I were to send that file to you, my settings wouldn’t necessarily work on your machine, but you’d have an entry for “3mm acrylic” that you’d created and optimized in your own curated materials library, and LightBurn could take that material type and apply your own best settings to it.

Similar to having your own multiple machines. I haven’t played much with the materials library, but if I understand correctly (and correct me if I’m wrong), this is kind of how this has been implemented on a local level. If you have a small machine (e.g. K40) in your lab for prototyping, and a big beast in your shop for production, you can tweak settings in their respective material libraries for a particular material, and if you assign that material to your layers, you can switch machines with impunity and get the results you’ve tweaked on both without thinking too hard about it.

I’m still green running multiple machines yet – I’m in the middle of re-braining a K40 to be able to talk to Lightburn.

“Normalizing” the machines is a sort of a related but unrelated thing. Being able to adjust your “zero point” and “100 percent” point, and/or calibrate your power curve to tube output power (e.g. 20mA = 75% power, 15mA=60% Power, etc.) would provide a bit more of a consistent baseline of similar power machines. I’ve often wondered with new materials where a good place to start calibrations would be. In my case, 42% gives me maximum rated current of 20-21mA on my tube, but being able to tell Lightburn that 42% = 100% (or with more granularity using tube power) would be extremely handy. I could say “hey, I’m looking to cermark a bunch of stainless tumblers! Where should I start. 1200x55 (60w) tube” – Another “calibrated” lightburn user could say “hey, I use Xmm/s at y% on my 60w” and it’d give me a good starting point, with less waste.

In addition, being able to cap your “100%” value at x%, where x% gives you the maximum rated current for your tube gives another layer of safety. While the DSPs I’ve used can set an upper limit for power in them, (e.g. if you set an upper limit at 75%, and request any more power than 75%, it won’t give you anymore) I’ve experienced my DSP going haywire because of a HV arcing problem. If you never request more than your “maximum” there’s no chance the DSP can “forget” its upper limit and tell the LPSU to give’er what for and blow your tube.

Power settings to me is an illrelavent issue.
The laser is a tool. If you want to baby it for a long life, fine.

Can you imagine a contractor doing wood framing on a house saying "I am sorry my circular saw only has a lifetime rating for cutting 100000 2x4’s so in order to make last longer I can only cut 100 2x4’s today then I need to let it rest till tomorrow?

If I need to use my 100w co2 laser at 100% to cut something, I will. Most likely though if iI need to use 100 % power I am using the wrong tool and should be cutting it on the cnc.
I will not baby it to extend the life of the tube. It is just a tool.
In general it seems that most Reci tubes that are sold at 100w are really just rated for 80% for a long life. Reci says for a W2 tube max current is 29ma but recommends max normal of 27ma and max 25 ma for 8000hr life. Reci also issued a warranty notice that upgrades the warranty to 540 days. So if I can get a year and a half out of tube by not going over 86 percent power I am fine with that. The most I have needed at this point was 75w but if need higher for task I will do it.
So it is pretty simple for me. Take a marker pen and write across the cover of the laser 86 w max. settings and I move on. Trying calculate a percentage of a percentage of a percentage every time I do something is just nuts.

I agree with you completely. I have always considered the tube a consumable item, and build the replacement cost into my pricing structure. At $1000 for my 120W tube, if I only get 2000 hours out of it, I only needed to add $0.50 per hour to my costs. If I can not justify a price increase of 50 cents an hour to my customers (When I already charge $1/minute for laser time) there is something completely wrong with my business model, and I should shut the doors immediately.

Chinese manufacturers tend to be “optimistic” about rating their equipment. I’ve run across several machines where a lower wattage tube has been greatly overdriven to get their advertised power. The “50W” machines I’ve seen have a ~40W tube (50x800mm, an actual 50w tube wouldn’t physically fit) in them being pushed hard over their limit to get that 50W number. I’d be surprised if they got even 10% of average life before a drastic reduction in power.

I’m not talking about setting limits on a machine to lock out the top end, I’m talking about figuring out where your tube’s redline current is, and putting your 100% there to avoid overdriving it. Not only will this give you a longer tube life, but it’ll give you a more predictable power curve at the high end.

For my part, and the reason I was thinking of this – I recently had a power supply go up in smoke, and I replaced it with a much bigger one in anticipation of replacing my tube the next time it burns out. Right now, in my machine for example, 42% on the new power supply drives the tube to redline. If I hit 100% and ran a job, I’d bet that even a brand new tube wouldn’t make it through the job being fed that much current. I’ll be going from 60W to 80W the next time I upgrade, and I didn’t want to buy a new power supply twice.

The tube may be consumable, but I don’t think it’s out of line to take a few minutes to make sure you’re running at rated specifications. A better analogy to me is putting 1 ton in a 1/2 ton truck. Sure, it’ll take it initially, and you might not care that it drastically shortens the life, but it’ll be touchy to drive, and a panic stop will really pucker you.

I can’t speculate on how your machines run, but I see Murphy and his law in my shop frequently. Without fail, every time a machine has thrown a tantrum, it’s happened right in the middle of a big, time sensitive job. The cost of a new tube is more or less irrelevant (usually the job it fails on will pay for it), but the time of replacing it, making sure the machine is aligned, servicing coolant loop, and kicking off a 6+ hour job at 5PM is not an experience I’d like to repeat very often if I can help it. People often provide their own stock as well, and having to call up and tell them there was a problem is one of my least favourite things to do.

In addition, as was pointed out to me earlier in the thread, not everyone is running commercial jobs on their machine. There are a lot of hobbyists who have a vested interest in preserving the life of their tubes. Even on the low end, a few hundred bucks for a generic 40w tube from a reputable supplier feels a bit steep to someone who isn’t running paying jobs.

You can already do that by asking for other’s material libraries. You had originally implied you wanted to be able to automatically adjust for power setting from tubes of different power ratings. That is where things get problematic. The drive current is not a good proxy for laser power for many reasons.

To recap, sharing materials settings for tubes of equal power rating is already possible. Using materials settings for tubes of different power ratings is a no go.

This makes the normalization you seek even more pointless. Bottom line, if you are that worried about it, you should buy a laser power meter. That is the only measurement that matters in the end. Not the drive current, the PSU power rating, or the tube size.

I don’t know what else to say. I think you’re over complicating things. Once you have developed machine settings for your own equipment, you never have to do it again.

Alternatively, you can just “send it” as @Grumpy_Old_Man and @RobDa suggest and not worry about optimizing power output.

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