Best way to control laser power with QtPlasmaC?

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17 Feb 2024 01:41 #293564 by shasse
As you've probably seen from previous posts, I'm working on using QtPlasmaC to control a fiber laser. Things are going well so far, including using a capacitive sensor for THC and "ohmic" sensing. I finally observed closed-loop THC today. I am now at the point where I can begin integrating the actual laser (a Raycus 500W laser to start). This laser has a 0-10V analog input for laser power, plus a "modulation" 24V signal to turn the laser on and off.

I have the 0-10V output working from a Mesa 7i92 PWM output and one of these: www.amazon.com/dp/B091B6LGXB?psc=1&ref=p...dt_b_product_details which seems to work with 3.3V despite the input being 5V.

I have the 24V modulation output working via one of these: www.amazon.com/gp/product/B07NWD8W26/ref..._title?ie=UTF8&psc=1

It seems simple enough to map the modulation signal to plasmac.torch-on. However, I am not sure how to handle the laser power. Spindle speed might be a logical choice, but I tried an M3 in the QtPlasmaC MDI mode to test that out and received an error that M3 was not allowed in MDI. Can anyone think of a logical way to control the analog laser power in QtPlasmaC? I looked at torch amps, but that does not seem to have a pin out on plasmac component. 

Thanks!

Scott
 

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17 Feb 2024 01:47 #293565 by phillc54
The torch amps is exposed on the pins qtplasmac.cut_amps-f and qtplasmac.cut_amps-s
 
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17 Feb 2024 01:50 #293566 by tommylight
M3 Might be OK for cutting, as i can not think of why it would need to change power during cutting, but will not work for marking/engraving as it stops motion when changing speed/power.
M67 might be much better, so here are some of my engraving machines using it, it uses PWM to regulate the pressure on the spindle:
forum.linuxcnc.org/show-your-stuff/46752...er-scratcher?start=0
Config files included on second post.
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17 Feb 2024 03:07 #293569 by shasse
M67 looks promising, thank you!

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17 Feb 2024 03:33 #293570 by shasse
Looking at this further I hadn't realized that QtPlamaC uses M3 to start the torch (just getting into this), so I'll probably try to hook up the spindle speed 0-100 to the laser power 0-100. Because M3 didn't work in MDI I originally thought the spindle was not used to control the torch. I presume M3 etc. disabled in MDI is a safety feature to avoid turning on the torch in a way that is not obvious to turn it back off?

Thanks!

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17 Feb 2024 08:08 #293586 by tommylight
M3 requires also $0 or $1 or $2 as LinuxCNC supports multiple spindles.
In QtPlasmaC, $0 is the torch, $1 should be scribe i think.
Might also need Sxxxxx as that is spindle speed, so
M3 $0 S100
Would be 100% laser power IF scaled correctly and set as spindle 0 in hal.
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17 Feb 2024 12:39 #293609 by shasse
tommylight your stone engraving setup definitely shows a very interesting way for doing laser engraving via M67. We do already have a dedicated fiber laser engraving/marking machine, but it is much smaller and lower power. So our short term goals for this machine are for cutting and for the power to be static for the whole job. So I'll probably start with using spindle speed for power with the idea to adapt to an approach that is synchronized with motion like M67.

As an aside, how did you generate the gcode for your stone engraver that uses M67 for pressure?

Thanks!
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17 Feb 2024 14:06 #293624 by tommylight
I use dmap2gcode from www.scorchworks.com to generate gcode.

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06 Apr 2024 22:22 #297717 by Uthayne
Scott,

I'm curious what the board you're using for the modulation signal is for and why can't you use pwm out directly? From what I gather from the Raycus manual, the modulation signal can drive the laser in a pulsed sense, or continuous. What does your modulation signal look like? I purchased the same boards as you to follow along.

Thanks

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07 Apr 2024 13:09 - 07 Apr 2024 13:14 #297745 by shasse
Our modulation signal is 24V and we aren't using any Mesa daughter boards, so we used one of these:

www.amazon.com/gp/product/B07NWD8W26/ref..._title?ie=UTF8&psc=1

They have the ability to switch at high speeds if we want to pulse the modulation signal, but right now we are just using the modulation signal to control the laser on and off. We're using the spindle on signal right now to drive that. Tommylight did some interesting work that would provide a basis for faster switching if we eventually wanted to engrave with the machine but we have a separate dedicated 50W engraver so for now we kept it simple and are just using this machine for cutting and laser on/off is driven with the spindle on signal.

We are running the "Continuous Wave Fiber Laser" laser source in "AD mode" mode (configured by sending +24V to a specific pin on the DB25 connector) so the laser takes an external 0-10V analog signal for power. We control that laser power signal via a hostmot 2kHz PWM output tied to spindle speed 0-100 and one of these:

www.amazon.com/gp/product/B091B6LGXB/ref..._title?ie=UTF8&psc=1

That is not completely linear, but it works well enough for our purposes.

I'll add that we're feeling our way through this process and are not fiber laser cutting experts by any means, so if you've got suggestions for us please don't hold back.

Scott
Last edit: 07 Apr 2024 13:14 by shasse.
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