Hi @lasertechs, I had my first go on the laser cutter last week after Brendon’s tutorial. Playing around with the settings, I was wondering if power literally means EM energy per second, or whether it is per pulse?
So if you increase the frequency with the power constant, does each pulse have less energy? Or does the total EM energy per second go up?
Cheers,
Will
Frequency is the pulse per second of the laser, higher frequency means higher pulse rate which means less energy.
Oh great. So the same power is spread over more pulses.
According to the Trotec manual, a higher frequency means higher pulse rate, which means more thermal energy that needs to be dissipated by the material you’re cutting, meaning the frequency does not affect the duty cycle.
I recommend making two test cuts of 4-6mm acrylic from the scrap bin and cut at 1000Hz (unsatisfying 
) and then one at 20.000Hz (very satisfying 
) at medium power-ish (educated guess!) or just recycle somebody’s acrylic setting in regards to the power. 
I’m afraid that’s a misconception. But please do correct me - I am absolutley happy to accept I got this wrong.
Oh really?
I could be totally wrong and used it the wrong way around all this years!
My way of looking at this has been:
More porous material- less pew pew
Less porous- more pew pew
Food for thought:
Take an ordinary lamp and each of the two experiments takes 60 seconds. You switch (pulse) the lamp on for one second, and then off. This “one second on” is the duty cycle.
In regards to “energy”:
Which one wasted used up more energy? 
If Ruby/Jobcontrol do as the operating manual states, the duty cycle stays the same, If the duty cycle would be variable, you couldn’t reliably determin the heat you expose the material to.
(I so hope 
, I got this right - mea culpa if this is not the right…)
You meant the right thing, because when quantifying electromagnetic waves, your statement is correct. But we’re not changing the frequency of the laser beam, just the frequency of the pulses.
In times like these, I wish we’d have the LaTeX plugin for markdown… Looking at an equation sometimes makes things 
Good that you mentioned duty cycle. As I know it, that’s the percentage of the time the laser is on for, relative to a full on-off cycle time. An example of a 50% duty cycle would be
on for 0.5 seconds,
off for 0.5 seconds,
that’s at a frequency of 1Hz.
If you increase the frequency, keeping the duty cycle the same, you’ll just get shorter on and off times, so 1ms on, 1ms off, would be 50% duty cycle at 500Hz.
I assume they keep it constant, otherwise higher frequencies would cut much deeper due to being on for a larger percentage of the time.
So as long as the duty cycle is constant for all settings, power could either refer to total energy per second, or the power of the laser while it’s on. But it doesn’t matter which because they’re always proportional given a set duty cycle.
I can’t find the term duty cycle in the pdf manual unfortunately so can’t verify this.
What you are describing would change the wavelenght of the laser and last time I checked, that is against the laws of physics. 
Power = lenght of one laser pulse, typically anything betwen 50 - 100ns (approx). Power set to 1% means shortest pulse, i.e. 50ns, power set 100% means 100ns.
Frequency = how many of those 50-100ns pulses (pew pews) do you fire onto the material during one second. Fewer pulses means less heat, that’s why you cut paper on the laser at low frequencies. To cut acrylic, you need more heat for a nice, smooth cut - but not too much heat, otherwise you end up creating goo.
Or in Petra’s words:
less pew pews (lower frequency) = less heat
more pew pews (higher frequency) = more heat.
Further reading (tho quite math-y): Paschotta, Rüdiger: Field Guide to Laser Pulse Generation. 2008, The Society of Photo-Optical Instrumentation Engineers (SPIE). [ISBN 978-0-8194-7248-9]
(Happy to lend you my copy)
You can increase the power of the laser without increasing the frequency of light. Just send more photons at a time.
But you could also increase the time averaged power by increasing the duty cycle.
So is the power setting in Ruby just duty cycle in disguise?
I would say “we don’t know how they regulate power” - it may be impulse length, intensity (ionizing voltage on laser) or combination of both.
Trotec doesn’t say anything on this I can find:
Depending on the exposure time, power level, and characteristics of your workpiece, the process results in the material evaporating, burning, melting, or changing color
Frequency … specifies the number of laser pulses per second. In a CO2 laser machine, the value can be set within a range of 1,000 to 60,000 Hz. For example, if you want to achieve a smooth edge when acrylic laser cutting, you need higher temperatures, thus meaning this value is set to at least 5,000 to 20,000 Hz. On the other hand, laser cutting wood a low frequency of 1000 Hz is necessary in order to achieve the brightest possible cutting edge (for example).
The Power laser parameter describes the output power of the laser. 100% is the maximum power. A higher power is needed for dark wood or stamp engravings, while lower values are used for materials such as paper.
The Speed laser parameter describes the movement of the laser head. Fast speeds lead to short exposure times, while slow speeds lead to long exposure times.
Here’s a bit of theoretical discussion on the subject of power/discharges in CO2 lasers:
tl;dr
the controller modifies the laser power by the length of time the laser is on for one dot period
So your answer is - yes it is duty cycle in disguise, with variable on and off times
Great. Thanks Roman. Query solved.
Wow! Wasn’t expecting that today but just learnt a lot of laser stuff…thanks 
“Hello Cleveland!”
Please promise not turning it up to 11… 
Let’s just agree to disagree. In order to “send more photons at a time”, you would have to change the amount of nitrogen atoms inside the tube. Unfortunately, this is fixed, so is the contents of CO_2… but please feel free to “believe” whatever you want.
Laser pulse generation is quite a theoretical beast, I highly recommend checking out the explanation from the book I recommended. The offer still stands, happy to lend it to anybody who wants to have a go.
I tried making a formula to determine setting for the laser, got a few absolute values with the formula that did work, however did not include the frequency, only power and speed. To be able to find the frequencies, I got to integers, and honestly I was getting a bit lost. Would be happy to meet up with someone with higher mathematics skills and show what I’ve done and possibly find out (and learn from?) the equation. Then make an application( in ideal world) .
The outcome would look like
Click on material
Set thickness
And it spits out settings.
Hi Petra, I’d love to do this. I was thinking of writing an equation myself, partly why I asked the question. My background is in physics, so should be doable.
Will
Hey Will, great. The next two months my availability will be only for online meeting, which I hope is sufficient?
OK, let me do a few more tests and enquiries first, then we can set up a call 