working with laser frequency

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sebastien laforet
Posts: 100
Joined: Wed Sep 07, 2016 1:23 am
Location: Lyon, France

working with laser frequency

Postby sebastien laforet » Tue Nov 29, 2016 8:03 am

has anyone tried to play with laser frequency? from what i understand from theory, if you decrease the frequency, you can (could?) minimize the output power per second.

so, at constant speed, if you set frequency at 10kHz instead of 20kHz (that's nominal value in rdworks), your material will (really?) receive only half power.

i believe this can be a solution for owners of relatively high power machines like mine (100W tube) where you can not set the output power under a certain value (15% for mine).

trying to cut paper, for example, either i burn it at low speeds / min power, or it cuts fine at higher speed, but the cuts line gets wobbly if the speed is to much and the path is curvy (no problem for straitght vertical/horizontal cuts). i believe i could reduce frequency and maintain the maximum speed that is "good enough" in shape.

at 100mm/s, i guess i can get decent curves, and a 10kHz frequency would get 100 "hits" per mm (10000 hits/s, 100mm/s --> 100 hits/mm), so it would not be noticeable since the kerf is greater than 0.01mm. theoretically, you could even go down to 1kHz for only 10 hits/mm and with a 0.1mm kerf it would still be relativelly ok, and with a min-min power at 5% of the previous min. (*)

one more point i have seen is that the speed of cut decreases in corner and small curves, so whatever the speed chosen, you input too much power if your source is too powerful. as you can NOT select a "min power" below 15% or it won't fire at all (in min/max power for the layer), the theory would be to set min power at 15%, reduce frequency so that corners are NOT burned, and set max power higher (maybe 30, or even 50%), since you can not set "proportional" frequency like you do for the power percentage.

obviously, this has to be tested, i'm not sure if the laser just fires at low frequency, and if the output power is regular enough. as i don't actually have access to my machine, i'm in hope that somebody has hindsight on this subject...

(*) in my case, "max" power is at 70%, and min at 15%. supposing the real power of the tube is 90W, the "min" power is 15/70*90=19.2 W, which is to much for high precision paper cutting. getting to 25% of this, around 5W, and a frequency at 5kHz would be theorically a great achievement.
Sébastien Laforet
machine : Bodor BCL-0605 (60x50) with 100W laser with TR origin.
Live in France
Primarily works laser for my wife (school teacher, so lots of boxes, letters, puzzles, ...) and miniature scenery (32mm scale : warmachine, infinity)

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Gene Uselman
Posts: 794
Joined: Thu Jul 07, 2016 1:18 pm
Location: Suburban Minneapolis, Minnesota, US

Re: working with laser frequency

Postby Gene Uselman » Tue Nov 29, 2016 9:02 am

This is an interesting theory, I have no idea if it is valid, but if someone has time to experiment I would love to hear the outcome. I, too, have a higher power laser and my operating window is 12% to 45% and I would love to be able to spread that out. I have not read anything pertaining to it. Gene
Gene- 130W 1300x900 China Laser with 2" FL lens
V8.01.19 RDWorks on Win 7 pro
500mm Z, blade table machine home is upper right.

100W Reci tube in a Bodor BCL0605MU V8.01.19
600x500x 200Z, SS table, 2" FL- mach home upper right
Vectric Aspire software- FlexiSignPro- vector/bitmap

Ron Gosnell
Posts: 44
Joined: Sat Dec 03, 2016 11:05 am
Location: Arkansas

Re: working with laser frequency

Postby Ron Gosnell » Sat Dec 03, 2016 5:54 pm

Hi guys,
I'm not going to say don't experiment but I have read that the frequency adjustments are more for the RF tubes and not the glass tubes.
Like every other topic it's hard to separate fact from folklore so just be careful. My understanding is that 20k is set for glass tubes.
Some say you can damage equipment but whether or not that's true or not is another story.

I would be more comfortable playing with a 40 watt tube rather than my 130 watt but I don't have one. I'm in the same dilemma as you are as my safety power ratio is 60% - 12% on my setup.
ThunderLaser Mars 90 130 watt 900 x 600 TL
Ruida 644XG Controller RDWORKS 8.01.18
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