First of all, thank you guys for this very well made software!!!
I have a doubt that the community could help me to fix
After years managing a fablab and playing with a trotec speedy 80w and having nice cutting edges on MDF 3mm at 500Hz, 28mm/s 80% power, I decided to build my own machine at home, with a CO2 tube, 80w.
I manage cutting same MDF with quite the same parameters but the edges are much more burned, it’s still ok but it’s black, not “caramel”).
After hours of reflexion, and if i understand, as tube laser does emit “continuous” beam" from analogic signal where RF tube is pulsed, this should explain the difference:
The RF heats less the MDF because it does less perforations per mm of cut (500Hz at 2.8mm/s=1400 dot/mm… invisible to the eye but cooler than continuous beam).
I use “perforation mode” to “pulse” my tube and I get a better result…but still not equal as the perforation mode has “only” 0.01mm resolution, equivalent to 0.28mm/pulse at 28mm/s, time enough for MDF to burn more…
So, if I am correct, I have 2 questions:
first: does playing a lot with “high frequency” perforation mode does affect my tube or its power supply?
second: if it doesn’t affect the material, would it be possible to get 10x more resolution to get 1ms pulse length? and so get to 1000Hz simulated (and from this, put 0.005s in perforation mode to get my 500hz ? and get my nice caramel color of edges?
Thank you in advance, and all my apologize for my english (did you ear the french accent?)
That’s at 20 mm/s, slightly slower than your 28 mm/s, but with only 60% = maybe 30 W of power, half of your 80% = about 60 W. Power comparisons based on PWM percentages don’t mean much, but should suffice for rough estimates: the edges on your MDF are blackened because they’re overcooked.
Rather than trying to replicate the RF laser’s behavior with the CO₂ laser, use LightBurn’s Material Test to find out what combinations of speed & power produce a good-looking cut with the machine you have.
I already did material tests, even at different offset for more playing in engraving mode. It is not my point.
I am talking about playing around physics, “hacking” a CO2 tube
Is pulsing (on/off) a continuous beam at high frequency (1000Hz) possible or not? (and I am NOT talking about twiking pwm frequency, stupid idea by the way…)
So why my 2 questions…
Does somebody have an idea?
The rise time of the power supply limits the minimum pulse width. The few specifications I’ve seen say “1 ms response time”, but it’s not clear what that means.
My measurements suggest the tube current rise and fall times are closer to 5 ms, so pulsing it any faster than 100 Hz simply won’t work:
Traces:
Yellow = X axis DIR for triggering
Magenta = L-ON
Cyan = controller analog output to HV supply
Green = tube current
The high-voltage power supply sends the controller’s PWM signal through a low-pass filter with a cutoff around 200 Hz, so “square” pulses above about 50 Hz are badly distorted.
The controller’s L-ON signal to enable & disable the power supply output has somewhat higher bandwidth, but it’s still on the order of 1 ms.
So a CO₂ laser is intended for continuous, rather than pulsed, operation. LightBurn’s Dot and Perforation modes are intended for low-frequency operation at relatively low mechanical speeds.
Note: I’m measuring tube current, not beam power, but it’s the best I can do with the instrumentation I’ve got.
that’s the answer I wanted to read, thank you much!!!
Yours results talk by themselfs
It’s already perfect for me! the scope is all!
So theoricaly possible to emit 5 ms pulse every 5ms, but it’s too low for perforation mode (0.01mm res.). But if I decide to cut the lines with perforation mode at 0.01mm/0.01mm, will it reduce the tube lifetime? …like when my 4 years old child turns the home light on/off fast?
I formulate differently, is this perforation mode (0.01/0.01mm) included in the CO2 laser tube standard use case? (even if it’s permitted in lightburn) or is it in the edge of the normal conditions of work?..my english is awfull…sorry
The dots are on 0.25 mm centers, but the layer ran at about 5 mm/s no matter what speed I set. The tiny spacing forced a very low speed, because the laser head never moved far enough to get up to the programmed speed.
There’s a difference between the GUI’s numeric resolution and the stepper motor + hardware resolution. My Ruida has a 12.0 µm/step resolution, which means the smallest possible step is 0.012 mm. Because it cannot step in exact multiples of the 0.010 mm resolution in the GUI, the smallest repeating distance would be 0.06 mm = 5 × 12 µm.
I expect attempting to produce 0.06 mm perforations will run into the same problem as the Dot mode above, with the machine running at an extremely low speed.
ok, thank’s, I will do more tests with dot mode.
I agree! and to be honest I didn’t check that point on my machine as it’s already enough for my use (but I will ). It is more “mind game” questionning than a pragmatic issue
(ok, I went to my workshop to check: 37.45µm … definitly a mind game unless I reduce more gear ratio)
To conclude, you 're right about materials differences, I saw a very interesting video about acrylic properties for best cutting…very strange material boiling (not burning) at 160° in my memory… I saw many sheets cut in the lab with beautiful results acrylic sheets cutting, but it’s another story…
I think I am done with this topic, thank’s again for your time and your technical answers!!!
… definitly a mind game unless I reduce more gear ratio)