I currently have a 20w Diode laser, and I just ordered a K40. Because each is capable of something the other is not, I am thinking of mounting the diode laser, or a quick mount, so I can have the diode and the CO2 in one machine. I am short on space, and I don’t sell anything, it is just hobby stuff.
I know I would need to protect one from the other, like lens covers, etc.
They can share a power supply, share the air assist, and share the enclosure. My Diode does not have an enclosure right now.
For a production shop, this would be a bad idea, but as a hobbyist, this seems like a way to have both, without the space being eaten up by both.
Thoughts?
I have a large 50watt CO2 I built and am devising a mount to use a diode head on it as well so far, I have found nothing negative other than losing a little space on the X-axis by having both heads mounted side by side
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There’s the additional inertia, which you might care about for raster engraving; you’d have to tune it for acceleration.
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A diode laser head weighs between 400 g and 600 g.
A good head for a small Co2 laser weighs around 150 grams.
The entire mechanical system is designed for these 150 grams. If this mechanism is then loaded with an additional 500 g, which need to be accelerated and decelerated quickly, I don’t need to do the math to know that it won’t work.
However, if your goal is to build the slowest laser in the world, then go for it.
Is it possible to add co2 head to diode mechanics, which is already built for heavier module? Or are there other differences in the mechanics than capability to handle heavier weight? And can one fine tune more powerful mechanics with software to better handle lighter load?
My system is quite strong, and I am using 42x42x60 nema 17 motors, which will handle a CNC: 2 motors on the Y and 1 on the X. It is handling the CO2 head with zero effort, so adding the diode to it should not make much difference, if any. I’m going to secure it to the CO2 head for a dry run to see how the mechanics work. I will be doing that over the next few days when I get a break from spring gardening.
It’s not so much about strength as acceleration. If it’s tuned for the most acceleration it can support, adding mass will make it lose steps unless it is closed loop, in which case it could degrade quality.
If it doesn’t suffer from adding all that mass, then you could have had run higher acceleration before the change. 
My plan would be to have the diode on a quick connection. That way I can use it when I want, but it is not thee all the time. I have bigger steppers to help with the acceleration. I have also been running my diode with Klipper. I have it working quite well and it allows for input shaping and a lot of tuning on the motion dynamics. My diode is a 20 watt, but I have removed everything except the main body. I have a CPAP plumbed to run air down through the body of the laser and come out at the nozzle for air assist. So, it’s lighter than normal. I haven’t weighed it, but I will.
I have an OMTech China Blue 50W and a few diodes. I have replaced about everything in the optical path from the tube and mounts, both mirrors, and the head. It also has NEMA23 motors on both X and Y axes.
I went the way of low mass rather than adding more to the head area that needed to move about.
I mounted my NEJE 30W (7.5W output, they claim) on my co2. I had worked with Sadler on his lightweight head and have the bearing screw patterns. It was relatively easy to build a replacement plate for the diode module.
If you have a dsp type controller (like a Ruida) you need to set it to work in digital mode by setting the tube type to RF (compared to glass).
You also only want to scan in 90 degree increments with a Ruida, likely all dsp controllers.
But, as @mcdanlj pointed out, the value here is acceleration. This two images from Lightburn preview shows you the plotted head movement. If you enable show transversal moves, it shows, in red, where the head is moving, even though it’s not lasing. Higher acceleration values mean shorter job times.
The only difference in these two is the controllers acceleration value. The left is 40000mm/s^2 and the right is 6000mm/s^2 (my machines stock value). In the lower right of each is the estimated job time… My machines current acceleration setting is 45000mm/s^2.
This only applies to raster scanning. Usually using vectors things are handled a bit different. Still applies, but to a lesser extent as far as I can tell.
Issues to keep in mind, focus distance… My table moves up/down, but the laser mount ends up being out of focus distance, so the mount may be different depending on the focus difference to the material. I had that issue with one of the led lasers I modified.
Notice it kind of hangs down lower. It’s weighs about 200 grams. I have double 3mm acrylic mount. They have interlocking parts and have all be glued together with a solvent.
I suspect you will have to lower your acceleration values if you want all of this stuff mounted on the head bearing. It would have to be balanced so you’d have to design a new mount for both of them so the weight is balanced on the bearing.
Be looking forward to photos of what you’ve done.
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