I’ve been able to try a different type of laser power meter. It’s this one:
It’s meant for CO2 lasers and will measure output from a 40W GF. I used the spiral vector image and “printed” into the center of the meter sitting on the crumb tray at Full Power. I removed the lens from the GF and exposed the power meter for 20 seconds. The exposure time for this digital meter is not critical. I ran it a few times and consistently got values ~23 Watts. That matches the results I received using the analog meter. I think it’s time I directly asked the GF engineers for some guidance. If you’ve read from the beginning of this topic, I’m in need of a actual laser power reading for research I’m doing on seeds.
Just an update…I’ve had a round of email exchanges with a Glowforge support person. She confirmed that the Glowforge modulates its power output on curves and turns so my idea of using a spiral to test the power output is a bad one. I’ve confirmed that my Glowforge-Basic is working properly since I can cut materials (e.g. thick, clear acrylic) with the default settings. I’ve also cleaned all the mirrors I can access. It occurred to me that if I measure the laser output before the light path enters the print head, it doesn’t matter what shape I print. For the Mahoney Analog Laser Probe I just need to know that the light path duration is 29 seconds and for the digital power meter that the light path lasts at least about 20 seconds. And…choose a shape that has no curves or corners. Therefore, I set up a print of a straight line that took the requisite time to print and made measurements with the two devices of the laser light coming to the print head. I used the 3D-printed sleeve for the Mahoney probe and placed the line to be printed near the top of the printing area. For the digital power meter, I placed the line to be printed near the bottom of the printing area and simply held the meter to the left side of the printing head during the print. This required that I fool the GF with magnets so I could have the front door open. Using these approaches, I found that my GF-Basic has a Full Power output of ~23 Watts, getting essentially the same value with both measuring devices.
Not if it’s modulating the power - that happens between the power supply and the laser tube. What’s coming out has already been modulated.
It makes sense because they have made a lot of changes to prevent overburning in curves (they used to not account for curves & corners could get crispy). They also spent a fair amount of time (& presumably money) on the tricked up power supply with power modulation capability. In fact there was a pretty significant delivery delay early on caused by problems with the power supply development.
Yeah, right, if the shape has curves or corners. That’s why I chose a straight line. Maybe that’s being modulated too???
Just wondering…doesn’t it concern you that a 40W machine is only outputting 23W? My measuring techniques may not be state-of-the-art, but the two vastly different measuring devices give me very similar values. Taking into account the background you shared of what GF went through to develop their machine, maybe it makes sense??? For me, since I’m trying to do something not meant to be done on the GF (e.g., etching seeds), I’m frustrated by the lack of control over the conditions. It’s likely going to force me to use a different laser to continue my work.
I’m still thinking there’s a flaw in the measurement process. This is my 3rd laser. I’ve had a “40W” that was actually only pumping out 32W of power, a 60W and the GF Pro.
The anecdotal evidence suggests that the GF is really in the 45W class based on cuts I’ve done on the other machines. If it were truly only 23W then I’d be seeing radically reduced cutting capability vs the other machines. Since I’m not (the opposite is true vs the 32W machine), the test must not be measuring correctly.
Even a straight line with the GF is likely to have power modulated due to the time it takes to get up to and down from speed. Otherwise it would overburn the ends of lines vs the middle. The other lasers had a test fire button that just fired the laser while the button is pushed. No movement or modulation involved. We’re trying to get similar results without being able to knowingly hold the laser to consistent power.
Yeah…I don’t think I’m measuring the actual Full Power of the GF-Basic either, but I’ve gotten so little technical help from GF to develop a protocol to get the most accurate values. Given that the “Power” values are unitless as are the “Speed” values, I don’t think GF really wants users to know the details. That’s not meant as a criticism since they probably have valid reasons for keeping things obscure. It’s just frustrating from a research standpoint.
For what it’s worth, power values are always going to be unitless from a user-interface perspective on whatever system, as far as I know. The best you’ll be able to get as far as power (without output measurements like you’re attempting to do here) is the input power in milliamps. But that doesn’t guarantee an output power so I don’t think it’ll accomplish what you’re needing for your research.
You obviously have a much deeper background in research than I do, so this may just be me taking up a few bytes of storage space on a server somewhere… You’ve performed a power test on the Glowforge (and unexpected results), then validated the functionality of the meter on another laser (receiving expected results). So, it seems like the next logical step is to perform an output power test on another Glowforge to see if you are in the same ballpark as the test on the original subject.
I think you’re right. I don’t own or have access to the kind of test equipment needed to make highly accurate laser output measurements. I’m thinking that the best I can do is clearly describe machine, its settings and any other relevant conditions for any seeds I etch and publish those. My goal in this research is not to develop a comprehensive “how to” on seed laser etching. I just want to show that it’s a viable approach to improving the germination of recalcitrant seeds. Thanks for the input!
I’ve been biting my tongue for weeks but every seed I’ve germinated has been in complete darkness, and I don’t think a single one ever failed to sprout. I dabble in aeroponics, individual seeds start out buried in damp, nutrient-enriched rockwool cubes, in complete darkness but a temperature-controlled container. My last girl was an avid at-home produce farmer and every seed she planted went underground.
I am, however, more of an experimenter than a maker - I’d be really curious to read anything you have on the benefits of this. Heck, I’d even give it a try, just for fun.
My work is focused on seeds that are dormant once they’re formed and cannot germinate until some kind of biochemical or physical barrier is removed. My application of laser etching is focused on the latter category including seeds that have hard (e.g., impenetrable to water) seed coats. After laser etching is complete, water enters the seed and germination commences. Not all seeds have dormancy issues, but many do.
Interesting. I’d (again) be curious to read any research you have (or links to others…) I closely follow agriculture-related topics. Mass-scale farming or at-home cultivation.