No it isn’t. People seem to think the percentage is a linear measure of laserness somehow but it isn’t. It is some hidden mapping to power that changes. Most likely
min power + (max power - min power) * percent /100
and min power is what was changed and changed back because it messed up Proofgrade settings. If PG settings had been stored as wattage then changing the min power would not have affected them or anybody’s hand made settings.
This is why I agree with @palmercr.
I totally get the ease of a percentile range(again that’s what this is, not a percentage), and can appreciate the simplification of what would appear to be an arbitrary number range to the lesser educated(in this area).
But as there are those who already know that difference and those willing to learn, having the ability to see/use a wattage setting isn’t a bad thing either. It would be beneficial too for going out and using another(gasp-but you’re on holiday and this maker-space with a red-sail 100w was the only place you could find to make “the macguffin” for “the dude” because of “the thing”) laser, regardless of maximum power rating, on similar items as you’d know a good starting point for what you want.
You’re making a big deal out of something that is an artifact of a temporary settings issue. So right now 1% engrave power means something more than that. But it’s not going to be that way forever. We know from an earlier software release they can make it 1% (or 1% of what’s available). We’re waiting on that. It would be no more useful to know that the current settings available are 35W - 40W in terms of actual use of the machine as 35W (if that’s what it is) is more than enough power to engrave most materials.
I have ma on my K40. I had to mark the dial on the adjustment knob because it doesn’t last under 4ma and I don’t want to push the tube to 100% power for lifespan reasons so I use 18ma as my max. A 1-10 indicator dial I made for the adjustment knob with 1=4ma and 10=18ma is fine.
On the Redsail I only see % power so I’ve set the machine config that max power is only 95% of the machine’s range. Again for purposes of preventing premature tube burnout. So “100%” power in the software is only 95% of the machine’s. And 50% is only 47.5% true. And it makes zero difference to my use. I calibrate jobs to the machine and if 50% indicated works that’s what I use and I haven’t lost a minute’s sleep wringing my hands that I should be using 47.5% because that’s the “real” machine value.
When you get the GF and it says 1%-100% not knowing if that’s 1W-40W or 3W-38W won’t matter a bit in real use.
BTW, for a variety of other reasons related to how materials react to sustained application of power, the “laserness” is not linear anyway. That’s the whole 1% power for 50 seconds is not equal to 50% power applied for 1 second (or in your view 1W for 50 seconds does not result in the same material ablation as 50W for 1 second).
I agree with palmercr’s initial post. Wattage would be a more robust defense against changes in the allowed minimum or maximum power produced by the laser. (To make it clear, the wattage palmercr is referring to is the wattage out of the laser, not the power dumped into the laser.) At first blush, it would also be easier moving projects between the basic and the pro and other laser cutters. Dan has already mentioned that each machine is calibrated before it is sent out the door, and that they have much tighter tolerances for the beam than other manufacturers in the ‘consumer’ space. So they know for each system the relationship between the power dumped into the tube and the power output from the laser. They have to know this so that different machines will produce identical results using the same settings for the same Proofgrade.
It’s also a valid point that we don’t set the length of a stitch on a sewing machine by a percentage between the smallest and largest stitches per inch that the machine can do. We don’t set the temperature of our water heaters as a percentage of maximum temperature the water heater can obtain. We don’t set the voltage of a power supply by the percentage of the maximum voltage it can produce.
But.
It’s not clear to me that a laser cutter is a linear device, where power to the material has a linear effect on the material. Does doubling the power allow for a cut twice as deep? I don’t think doubling the power of a photo engrave doubles the darkness of the engrave. As the power increases the dot size gets larger but not in a linear way, and more power goes to making the dot deeper which affects the dot size as well.
The effect of the beam quality also affects the performance of a machine. It is not correct to say one will get the same results from 30 watts on the Glowforge as 30 watts on a K40 or Redsail. (I don’t know if those show power out versus power in.) Correcting for the beam area doesn’t help because the power profile of the beams are different, and the focusing cones are different.
In other words regardless of the starting point, watts or percentage, one still has to futz around to get the desired results on non-Proofgrade material.
And.
I’ll assume dan and company are pretty smart people and they considered using watts instead of percentages. Why didn’t they? Probably due to the support issues that would engender. Remember the target market for the Glowforge. I don’t want to consider how many people would complain that they can’t get their machines below the minimum wattage, which would be non-zero. Or more importantly, as tubes age the power produced gets lower as CO2 migrates into the tube. That 40 watts will no longer be 40 watts and that will cause confusion. And support issues. Or the alignment might get whacked, the beam profile might change, and again that 40 watts will no longer be 40 watts.
We also know the optics are better on the pro. Which means the beam profile could very well be different between the basic and the pro. Which means that again one can’t just correct for the beam area and expect the same cutting/engraving behavior from the two devices.
Wattage can be measured extremely precisely, but that precision implies a precision that the Glowforge simply can’t deliver. And that will cause support issues.
So.
I’m not going to second guess dan and company. As already shown, people can produce great work with the systems at hand without too much difficulty once they get the process down. And the learning curve wouldn’t change whether power was marked in percentage or watts.
It is a PITA that the low power settings aren’t enabled as production units are being shipped. I don’t know if people’s work flow will have to change once this is enabled for non-Proofgrade materials (or for dialed in settings used on Proofgrade), or if the machines don’t allow the user to set a low power. In either case, as what happened when they were turned on during for a while, this is going to cause support headaches when it is turned on.
Spot on. And it’s not just GF - it’s all lasers. That precise wattage is very precise data. It is not very precise information. People using this in real life can’t take advantage of the precision of the data because the information that data provides is what limits the actionable use.
I think this is always the case with a CO2 tube. There is a minimum current that sustains stable output, so I don’t think you can achieve 1%. That is why I object to percentage starting at 1.
The closest you will get to “laserness” is wattage over speed. That is the amount of energy put in. Any non linearity in its effect is entirely material dependent. Things like conductivity, specific heat capacity, latent heat of vaporisation, etc. So I don’t think you can get a better measure.
Extreme changes like 1% for 50 seconds and 50% for 1 second probably give very different effects but going twice as fast at half the power is likely to be similar and a good starting point. If you have a false percentage scale where 1 is not 1% how do you double it or halve it?
It works on my Redsail every single time I use it. Not theory. Reality. The way I have it set 1% is the min the machine will lase at. 100% is 100% of available power even though I have it throttled to 95% of the machine max. It makes absolutely no difference to me that I’m really only getting 29.5W instead of 30W when I set it for 50%.
I have never had a student struggle with the ability to use % vs watts.
You don’t need to keep fretting that 1% is not 1/10th of 10% now. It’s temporary.
If the min current is 4mA, out of 18mA then isn’t your 1% actually more like 22%?
So 50% is a long way off 30W, not just half a watt, which I agree would not make a noticeable difference. I am not trying to split hairs here. My understanding is you can’t get lower than something like 15-20% power so if that is represented by 1% it is misrepresentation.
If the new settings can actually achieve 1% then it is straight forward to calculate the wattage and 50% will be half power, but I don’t think that is the case.
Just curiosity on my part Chris…what do you plan to do with the Glowforge once you get it?
What will you be creating/making?
I am only saying this tongue in cheek with a smile, not a smirk… Seems like an answer might be, immediately taking it apart and decoding the firmware to see how it could have been made better.
I’m sure there has got to be some creativity involved in there somewhere, otherwise, why not get a $400 laser to deconstruct instead of a $3000 one? (Or however much was paid.)
That wouldn’t make any sense at all.
I bought it to make these and sell them: https://www.thingiverse.com/make:155111 but that ship sailed a long time ago but I will probably make a couple for myself.
I am also designing a new 3D printer so I will cut an acrylic door for that if it arrives in time. If it works well I will scale it up and make a large version. That will need the pass through working.
I have a few electronic projects that I want to engrave the front panels for. I think engraved text on black DiBond should look good. I also have some thick Delrin that I want to cut but that will need the double sided cut feature.
I plan to make a pick and place machine and I will make some parts for that.
I originally planned to do some 3D parts with it but I don’t think I will be able to do micro machining with it now.
We have horrible door handles in every room that have large oval escutcheons that won’t be covered by new ones as they are all round or rectangular nowadays. So I will need to make a lot of wooden escutcheons to cover the marks left by the old handles.
I don’t have any artistic ability so I will probably use catalogue designs to make gifts, etc.
I am not sure what else. I 3D print things all the time but I don’t think I will use the laser as much.
I am currently building a very precise but tiny 3D laser printer and will compare the results to try to get to the bottom of the engraving ripples.
I look forward to the open source GF firmware that was promised.
Huh! Oddly enough, I also bought into it to make a 3D printer enclosure, which I still haven’t gotten around to making yet. Guess I will one day. (Honestly, MakerGear will probably offer one for sale before I get around to it.) 
You’re mixing up machines. The K40 is the one limited to 18ma and it is controlled by a knob on the panel that has no markings coming from the factory. It’s the power approach you like (just using amps vs watts). There is no way to adjust the power in the software. There is also no way to mix operations and power in the same job. Since the machine lases at 4ma and it burns the tube out somewhere over 20-22ma, my “100% of available power” is a range from 4 to 18ma. I have created a dial for that one that is segmented by the #s 1-10 spread across that 14ma range. Each tick is a 1.4ma increment of power or a 10% step. It is entirely irrelevant that this represents less than 40W or more than 4W. Chinese lasers are rated by over boosting the tube. The actual tube rating of most 40W Chinese laser tubes is in the order of 30-35W. Mine happens to be 32W at 20ma. (Measured)
The Redsail is a 60W laser. That one does not allow me to set power using a knob but it does have a power meter (again in amps). The power is set in the software as a %. I also have the ability to set machine configs that override the software. I did that for max power (in percentages). Since I have set the max power set to 95% at the machine config, the software’s 100% is only 95% of the machine’s rated power which I assume but don’t know via measuring is 60W.
50% power in the software is where I get the expected 30W in your approach but since I have the machine set to override the max, the 50% software setting is half of 95% of the machine’s rated power.
The point is it doesn’t make a whit of difference in real life. I set a % and give it a test (I have calibration designs that step through power & speed settings that I use for initial settings). If I need to I adjust. I don’t care whether I adjust 30% power to 40% or if I were to set it from 17.1W to 22.8W. Both are the same thing but my wife & kids are much happier with % settings than W settings and they don’t even care if it’s a percentage or an arbitrary 1-100 or 1-50.
It also doesn’t matter to them or me whether the machine is capable of 60W of power and my 100% is only 57W. All I’m using is 57W and if I want to pretend that’s 100% that works. It doesn’t matter that the machine is capable of another 3W of power. In fact it’s probably capable of 65 or 70W but only for a few minutes.
In your approach is the power you want to use the max tube life 57W, the reduced tube life but machine rating of 60W or the real tube max before burnout of 70W?
If your real life experience says you need to deal with watts, you’re not going to get what you need with the GF. You bought a machine that doesn’t provide watt information and isn’t likely to in the near term. Time to find a machine that gives you what you think you need.
The GF is rated at 45W and unlike Chinese machines I think that is the true rating and Dan has said we don’t need to under run it. So I expect 100% to be 45W and be usable. If 1% is significantly more than 0.45W then that is misleading and 50% is not half power, etc.
It’s not a big deal. I am sure I can work out the mapping if I had a machine but I think the machine would be easier to use with wattage unless the % scale ends up linear. Starting at 1% and hiding the fact that CO2 tubes have a minimum power doesn’t help anybody understand what is going on.
That sounds very similar to the sorts of projects I have in mind for a laser.
The speedometer in my jeep reads 5mph when I am parked, 'cause that’s where the stop pin is.
So maybe you knowledgable folks can clear some things up for me.
I’ve been thinking a 40W laser like the basic meant put in much greater than 40W of power due to inefficiencies and get out up to 40W of optical power. But the above discussion of input amps makes me think it’s put 40W into the laser tube get out much less?
Yes, you’re right, it’s not a big deal.
I’m just as analytic as you, if not more so. It just seems to me that given the fact the machine is not linear in ‘wattage -> desired cutting/engraving output’ that the calibration of ‘desired output -> settings’ is the one to use. Using ‘desired output -> wattage -> settings’ is robust against changes in min and max laser power (in that ‘wattage -> settings’ is easy to measure), but adds a step in the process for all time.