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Laser Recommendations for Large Format CNC Fabric Cutter (that's not CO2)

keep-it-real

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K I've been digging through these forums for a while now and haven't quite found my answers. I recently built a 8' x 5.5' CNC machine to cut fabric using an Openbuilds Blackbox controller and paired it with a JTech Photonics 7w 445nm diode laser. I knew the choice of laser was a bit of a gamble, and it... mostly works. I'm able to cut darker fabrics at 10 IPM and kinda cut white/lighter fabrics at about 5 IPM. So yes it works, but it's definitely slower then expected and it leaves me looking for other options.

I'm hoping to avoid a CO2 set up because I have a fixed bed (without a Z axis) and I'm just not excited about the open laser and mirrors. Seems like a lot of complexity to me relative to the simplicity of the single diode. Feel free to just talk me into it cause I realize it is likely one of the most effective solutions.

K any suggestions on higher power lasers that could attach directly to the X-axis plate? And is there a wavelength that would work best for all colors of fabric? I'm mostly cutting nylon and polyester blends but plan on cutting more organics as well.

So far my best options seem to be an Coherent FAP800 (probably a 60w) which I'd probably gamble on again and buy one through ebay. If I went this route, I'd probably purchase this driver (recommendation by Alaskan): Laser Diode Driver 75A for Jenoptik, Coherent Pump YAG, YVO4,..Japan (I can't post links yet cause I'm new here but put that into ebay). I've heard that these have a pretty bad beam quality but I don't think that's super important for cutting fabric (I don't need any precise engraving ya know). Recommendations on a fiber and focusing lens that's compatible? Would you mount this directly to the x-axis plate or mount the FAP on the side of the machine and run the fiber through 10' of drag chain? Do you see any safety issues with this specific setup (including a used FAP) and leaving it running for long cut times on a CNC?

The other option could be the new 15w laser from optlaser: PLH3D-15W Engraving Laser Head Universal Kit (again at optlasers.com, first one in CNC and 3D section). Anyone know if this is truly 15w of optical power? I was under the impression that single diodes maxed out around 7w. I'm choking on the price tag a bit but I'd do it if I had to.

Any other recommendations for some legit cutting power? I'm hoping for the simplest plug 'n play solution possible but I'm also willing to go DIY if needed. I'm relatively new to lasers so I apologize if there are any obvious knowledge gaps above!
 



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Hey keep-it-real,

A key thing to understand about how laser cutting works is that it's not quite a knife (even though commercial laser cutters make it look that way!), it's the use of light to get part of the material so hot that it burns, melts or vaporizes. So when you're thinking about cutting something with a laser, you're really thinking about what very concentrated high temperatures will do to the material. The reason CO2 lasers are versatile is their high power and ability to focus well - by delivering a huge amount of energy to a tiny point, almost any material is going to vaporize very quickly, resulting in a clean cut (but even then there are some off-limits materials, because some things produce extremely toxic gasses when they burn, which remember is fundamentally what the laser is doing). Since you already know the specs of the laser you have and know how it performs for you, I guess the short answer is it depends if the current laser you have is 7W optically or electrically. If it's 7W optically, you're not going to do much better, that's as powerful as diode lasers come at the moment. If it's 7W electrically, yes there are more powerful laser modules around that might give you better results, but even they aren't quite perfect. Here's a few points that might help steer you as you keep looking into this stuff.

*Quick note - Since you have experience with lasers and laser cutting, I'm guessing you know a lot of this stuff already, and I'm not insinuating that you don't! I'm just going to run through all the fundamental points because that's easier than trying to guess exactly what your level of experience/background knowledge is and how much research you've done already. If there are one or two things in here that help you out or give you some new information, great! The rest can be a resource for less experienced people who come across this thread. If you're at the point where you're looking for more technical information or have questions specific enough that nothing in here is particularly helpful, please feel free to ask them or send them my way, and I'll do what I can to give answers/explanations better tailored for you.

Power:
Even though diode lasers can be extremely powerful, even the best single diode laser is an order of magnitude less powerful than even a mid-tier CO2 tube. For that reason, most diode-based laser CNC devices are best thought of as laser engravers, rather than laser cutters. If you set them to move slow enough, they certainly can cut through thin materials, but in so doing, they tend to do a lot more damage to the surrounding area and give you a less clean cut. Imagine a 80W CO2 laser as a red hot wire cutting through plastic - it's going to make a fairly clean cut because it melts through so fast the rest of the plastic doesn't have time to get hot. In this respect, a diode laser is more like a knife you're warming with a lighter. Sure it will work, but getting the part of the material you want to melt hot enough will take so long that a lot of material around it is going to start to char and melt too.

Wavelength:
Different wavelengths have different advantages and disadvantages when it comes to laser cutting. Depending on how much experience you have with lasers (or just with light in general) you know that when it comes to the lasers most people use as a hobby, "darker colored" things tend to burn more effectively. Again, this might be totally obvious to you, and if so sorry, but I think it bears repeating so that you keep it in mind for your application. The reason this happens is because materials that look "dark" in color to us absorb a relatively large percentage of the visible light that hits them across a wide portion of the visible spectrum. If it looks dark to your eyes, that's precisely because it absorbs visible wavelengths well, indicating that visible wavelength lasers will also be well absorbed. This isn't set in stone though, as different colors can be produced by different mechanisms. CO2 lasers are different for a few reasons. First, they're infrared, meaning that how a material looks visually doesn't tell us anything about how the light will interact with it, because we can't see the infrared light either being absorbed or reflected by it. One of the advantages to the high power of a CO2 laser is that even if the wavelength is absorbed poorly, there's so much excess power to go around that it still might work decently. Because diode lasers are comparatively less powerful, wavelength selection matters a lot more, and not every diode is going to work well for every material.

Beam:
Laser engraving and cutting applications need a very well focused beam. I know you mentioned that you aren't trying to do extremely fine detail work, but that isn't really why focus matters. It's all about the density of the delivered power. A less focused beam won't just cut a thicker line, it will take much much longer to cut through the material, if it does it at all. If you have your heart set on a diode, you'll ideally want something called single-mode, particularly one called TEM00. Basically this is a beam that looks how you'd imagine a laser looks - brightest at the center and dropping off in a uniform circle outward. These beams can be focused tightly and so are ideal for delivering maximum power to a small area. Other beam modes have odd energy delivery shapes, where they look more like bullseyes or even flower petals rather than a single spot, meaning even with the best focus, the energy isn't going to be as concentrated. And bear in mind, you can't reliably tell the mode of the laser by how its spot looks to you (with goggles on of course!) - the optics can introduce abberation that looks like concentric rings, making it hard or impossible to tell. Unfortunately, a lot of the highest power laser diodes are known as multimode, meaning you're not getting that single fundamental mode that can be focused ideally.

Mechanical:
You mention that one of the reasons you don't like CO2 lasers is that the mirrors seem fiddly, and thats absolutely true. Getting the mirrors aligned is difficult and is inherently a trial and error process, and if the mirrors get dirty, they're going to start absorbing the laser light, both reducing your cutting power and causing thermal damage to the mirrors themselves. Even though this is a weakness, it's actually an advantage over diodes - right above the cutting zone is a dirty place. Smoke, ablated particles, etc. A mirror can be cleaned or even replaced, but if that smoke and debris damages the laser optics, you could potentially have a much bigger/more expensive repair on your hands, if you can do it at all. That's why a lot of CO2 laser cutters have an attachment right near the cutting head that blows pressurized air directly at the point that the laser is burning. This not only clears away smoke that can absorb light and reduce cutting power, it also keeps the smoke and debris away from the sensitive optics.

Safety:
I'm going to spare you the introductory version of the safety talk because it looks like you have experience, but there are some specific safety things going on here that you need to think about. Obviously, you need high quality laser goggles any time you're using a powerful laser. Your retinas are far far easier to engrave than any material, and infinitely less replaceable. As for specific safety matters with this application, it's easy to think that this setup is marginally safer because the laser is fixed pointing down at the work surface, but that's not the case. When materials burn and melt they can become much more reflective than they are normally, and the irregular shape means that reflected light is going everywhere. Not to mention, if you did end up going with a mirror based design, you need to be extra careful. If you bump one of those mirrors, not only are you going to throw off the calibration of your system, you're going to get a full power beam shooting off in an unexpected direction. Wherever you use this needs to be a controlled area where you know that no one is going to be around the laser when it's running. Even then, I'd highly recommend building an enclosure for the laser, this is both good for blocking stray light from getting out, and containing the large amount of smoke any laser cutting setup generates so it can be sucked away by a ventilation system you'll also have to build.

One last note, you mentioned those laser modules being listed as "15W" or something along those lines - that is not 15W of optical power. That marketing practice isn't quite as deceptive as those obviously bogus ads for like "30W BURNING LASER POINTER BUY NOW!", but what they're doing is stating the electrical power consumption of the module, which includes all the losses introduced by the driver circuit. As far as I'm aware, the most optical power you're going to get out of a diode based module is about 7.5 watts in most cases.

I know that was a doozy of a post, sorry for the reading assignment. Basically, I wouldn't give up on CO2 lasers just yet if you have your heart set on cutting things. Until there are some big advancements in the power capabilities of diode lasers, CO2 is just better for cutting in most cases. I know diode lasers have a big price advantage, but there are inexpensive CO2 lasers out there, and rather than building one from scratch, you can look into buying one of the inexpensive ones and modifying it to be more capable and suit your needs. Diode lasers can be great though, just not ideal for cutting patterns out of fabric, as you've experienced. I'd be thinking of using a diode laser to engrave things, like you could burn really cool designs onto leather (REAL LEATHER please, fake leather is often made of PVC, which produces lethally toxic furans and dioxins when it burns).

I hope I was able to answer some of your questions and give some advice, if you want to know more/have questions about any of the stuff I mentioned, please don't hesitate to ask!

Cheers,
LM
 
Last edited:

keep-it-real

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Hey keep-it-real,

A key thing to understand about how laser cutting works is that it's not quite a knife (even though commercial laser cutters make it look that way!), it's the use of light to get part of the material so hot that it burns, melts or vaporizes. So when you're thinking about cutting something with a laser, you're really thinking about what very concentrated high temperatures will do to the material. The reason CO2 lasers are versatile is their high power and ability to focus well - by delivering a huge amount of energy to a tiny point, almost any material is going to vaporize very quickly, resulting in a clean cut (but even then there are some off-limits materials, because some things produce extremely toxic gasses when they burn, which remember is fundamentally what the laser is doing). Since you already know the specs of the laser you have and know how it performs for you, I guess the short answer is it depends if the current laser you have is 7W optically or electrically. If it's 7W optically, you're not going to do much better, that's as powerful as diode lasers come at the moment. If it's 7W electrically, yes there are more powerful laser modules around that might give you better results, but even they aren't quite perfect. Here's a few points that might help steer you as you keep looking into this stuff.

*Quick note - Since you have experience with lasers and laser cutting, I'm guessing you know a lot of this stuff already, and I'm not insinuating that you don't! I'm just going to run through all the fundamental points because that's easier than trying to guess exactly what your level of experience/background knowledge is and how much research you've done already. If there are one or two things in here that help you out or give you some new information, great! The rest can be a resource for less experienced people who come across this thread. If you're at the point where you're looking for more technical information or have questions specific enough that nothing in here is particularly helpful, please feel free to ask them or send them my way, and I'll do what I can to give answers/explanations better tailored for you.

Power:
Even though diode lasers can be extremely powerful, even the best single diode laser is an order of magnitude less powerful than even a mid-tier CO2 tube. For that reason, most diode-based laser CNC devices are best thought of as laser engravers, rather than laser cutters. If you set them to move slow enough, they certainly can cut through thin materials, but in so doing, they tend to do a lot more damage to the surrounding area and give you a less clean cut. Imagine a 80W CO2 laser as a red hot wire cutting through plastic - it's going to make a fairly clean cut because it melts through so fast the rest of the plastic doesn't have time to get hot. In this respect, a diode laser is more like a knife you're warming with a lighter. Sure it will work, but getting the part of the material you want to melt hot enough will take so long that a lot of material around it is going to start to char and melt too.

Wavelength:
Different wavelengths have different advantages and disadvantages when it comes to laser cutting. Depending on how much experience you have with lasers (or just with light in general) you know that when it comes to the lasers most people use as a hobby, "darker colored" things tend to burn more effectively. Again, this might be totally obvious to you, and if so sorry, but I think it bears repeating so that you keep it in mind for your application. The reason this happens is because materials that look "dark" in color to us absorb a relatively large percentage of the visible light that hits them across a wide portion of the visible spectrum. If it looks dark to your eyes, that's precisely because it absorbs visible wavelengths well, indicating that visible wavelength lasers will also be well absorbed. This isn't set in stone though, as different colors can be produced by different mechanisms. CO2 lasers are different for a few reasons. First, they're infrared, meaning that how a material looks visually doesn't tell us anything about how the light will interact with it, because we can't see the infrared light either being absorbed or reflected by it. One of the advantages to the high power of a CO2 laser is that even if the wavelength is absorbed poorly, there's so much excess power to go around that it still might work decently. Because diode lasers are comparatively less powerful, wavelength selection matters a lot more, and not every diode is going to work well for every material.

Beam:
Laser engraving and cutting applications need a very well focused beam. I know you mentioned that you aren't trying to do extremely fine detail work, but that isn't really why focus matters. It's all about the density of the delivered power. A less focused beam won't just cut a thicker line, it will take much much longer to cut through the material, if it does it at all. If you have your heart set on a diode, you'll ideally want something called single-mode, particularly one called TEM00. Basically this is a beam that looks how you'd imagine a laser looks - brightest at the center and dropping off in a uniform circle outward. These beams can be focused tightly and so are ideal for delivering maximum power to a small area. Other beam modes have odd energy delivery shapes, where they look more like bullseyes or even flower petals rather than a single spot, meaning even with the best focus, the energy isn't going to be as concentrated. And bear in mind, you can't reliably tell the mode of the laser by how its spot looks to you (with goggles on of course!) - the optics can introduce abberation that looks like concentric rings, making it hard or impossible to tell. Unfortunately, a lot of the highest power laser diodes are known as multimode, meaning you're not getting that single fundamental mode that can be focused ideally.

Mechanical:
You mention that one of the reasons you don't like CO2 lasers is that the mirrors seem fiddly, and thats absolutely true. Getting the mirrors aligned is difficult and is inherently a trial and error process, and if the mirrors get dirty, they're going to start absorbing the laser light, both reducing your cutting power and causing thermal damage to the mirrors themselves. Even though this is a weakness, it's actually an advantage over diodes - right above the cutting zone is a dirty place. Smoke, ablated particles, etc. A mirror can be cleaned or even replaced, but if that smoke and debris damages the laser optics, you could potentially have a much bigger/more expensive repair on your hands, if you can do it at all. That's why a lot of CO2 laser cutters have an attachment right near the cutting head that blows pressurized air directly at the point that the laser is burning. This not only clears away smoke that can absorb light and reduce cutting power, it also keeps the smoke and debris away from the sensitive optics.

Safety:
I'm going to spare you the introductory version of the safety talk because it looks like you have experience, but there are some specific safety things going on here that you need to think about. Obviously, you need high quality laser goggles any time you're using a powerful laser. Your retinas are far far easier to engrave than any material, and infinitely less replaceable. As for specific safety matters with this application, it's easy to think that this setup is marginally safer because the laser is fixed pointing down at the work surface, but that's not the case. When materials burn and melt they can become much more reflective than they are normally, and the irregular shape means that reflected light is going everywhere. Not to mention, if you did end up going with a mirror based design, you need to be extra careful. If you bump one of those mirrors, not only are you going to throw off the calibration of your system, you're going to get a full power beam shooting off in an unexpected direction. Wherever you use this needs to be a controlled area where you know that no one is going to be around the laser when it's running. Even then, I'd highly recommend building an enclosure for the laser, this is both good for blocking stray light from getting out, and containing the large amount of smoke any laser cutting setup generates so it can be sucked away by a ventilation system you'll also have to build.

One last note, you mentioned those laser modules being listed as "15W" or something along those lines - that is not 15W of optical power. That marketing practice isn't quite as deceptive as those obviously bogus ads for like "30W BURNING LASER POINTER BUY NOW!", but what they're doing is stating the electrical power consumption of the module, which includes all the losses introduced by the driver circuit. As far as I'm aware, the most optical power you're going to get out of a diode based module is about 7.5 watts in most cases.

I know that was a doozy of a post, sorry for the reading assignment. Basically, I wouldn't give up on CO2 lasers just yet if you have your heart set on cutting things. Until there are some big advancements in the power capabilities of diode lasers, CO2 is just better for cutting in most cases. I know diode lasers have a big price advantage, but there are inexpensive CO2 lasers out there, and rather than building one from scratch, you can look into buying one of the inexpensive ones and modifying it to be more capable and suit your needs. Diode lasers can be great though, just not ideal for cutting patterns out of fabric, as you've experienced. I'd be thinking of using a diode laser to engrave things, like you could burn really cool designs onto leather (REAL LEATHER please, fake leather is often made of PVC, which produces lethally toxic furans and dioxins when it burns).

I hope I was able to answer some of your questions and give some advice, if you want to know more/have questions about any of the stuff I mentioned, please don't hesitate to ask!

Cheers,
LM
Thanks for the reading assignment LM! There were some good gems in there. I was reading it on my phone initially and didn't realize how long I'd be scrolling for! Love it.

Here are some bullet point replies (in no particular order):
  • Yes, my current laser does have a 7w optical output from a trustworthy source.
  • Note taken on the advantages of the CO2 setup. I'll continue to explore other options first but if I can't find anything, I'll convert it to CO2. I was close to just buying a commercial CO2 laser first and if I had to do it over again, I probably would. This entire project was a bit of a gamble with the single diode but it was and still is, worth a shot. Since I already have the gantry built, I'll probably try converting it to CO2 before buying a new one.
  • Honestly, if my current setup could cut white fabric better at the same 10 IPM as the darker fabric, I'd just stick with it. I have to run it at 5 IPM for it do do anything and even then, I have to tear out the pattern pieces and end up ripping some of them in the process.
  • With a little more research, the 15w laser from optlasers has multiple diodes in it so I actually do believe that it is truly 15w of optical power. Optlasers seems to be coming up often as a good source. I'm undecided due to the price but I'd consider it.
  • The Coherent FAP800 still seems like an excellent option especially if I can run the fiber through the drag chain without any issue. This would keep some weight of the axis and allow me to water cool the diode at the side of the machine. My biggest questions here are safety and if the beam can be focused well enough to cut. Any specific knowledge about cutting capabilities with the FAP's would be lovely.
  • For both of our assurance, the machine is vented to the outside, there is no enclosure (yet) but the JTech diode comes with its own enclosure around the beam and protective glasses are always worn in the same room. If I do convert it to CO2, I will definitely build an enclosure. Last, I am aware of the chlorine gasses produced by burning PVC so I certainly won't be cutting vinyl! Check.
Hope those points provide some insight and thanks again for your expertise! For other readers, my two biggest questions are 1. about the Coherent FAP800, it's cutting capabilities, and what driver, fiber, lens, and cooling system you used. And 2. if you're aware of any other higher power lasers that can cut fabric and could be mounted directly to the x-axis plate or via fiber. Cheers.
 
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Thanks for the reading assignment LM! There were some good gems in there. I was reading it on my phone initially and didn't realize how long I'd be scrolling for! Love it.

Here are some bullet point replies (in no particular order):
  • Yes, my current laser does have a 7w optical output from a trustworthy source.
  • Note taken on the advantages of the CO2 setup. I'll continue to explore other options first but if I can't find anything, I'll convert it to CO2. I was close to just buying a commercial CO2 laser first and if I had to do it over again, I probably would. This entire project was a bit of a gamble with the single diode but it was and still is, worth a shot. Since I already have the gantry built, I'll probably try converting it to CO2 before buying a new one.
  • Honestly, if my current setup could cut white fabric better at the same 10 IPM as the darker fabric, I'd just stick with it. I have to run it at 5 IPM for it do do anything and even then, I have to tear out the pattern pieces and end up ripping some of them in the process.
  • With a little more research, the 15w laser from optlasers has multiple diodes in it so I actually do believe that it is truly 15w of optical power. Optlasers seems to be coming up often as a good source. I'm undecided due to the price but I'd consider it.
  • The Coherent FAP800 still seems like an excellent option especially if I can run the fiber through the drag chain without any issue. This would keep some weight of the axis and allow me to water cool the diode at the side of the machine. My biggest questions here are safety and if the beam can be focused well enough to cut. Any specific knowledge about cutting capabilities with the FAP's would be lovely.
  • For both of our assurance, the machine is vented to the outside, there is no enclosure (yet) but the JTech diode comes with its own enclosure around the beam and protective glasses are always worn in the same room. If I do convert it to CO2, I will definitely build an enclosure. Last, I am aware of the chlorine gasses produced by burning PVC so I certainly won't be cutting vinyl! Check.
Hope those points provide some insight and thanks again for your expertise! For other readers, my two biggest questions are 1. about the Coherent FAP800, it's cutting capabilities, and what driver, fiber, lens, and cooling system you used. And 2. if you're aware of any other higher power lasers that can cut fabric and could be mounted directly to the x-axis plate or via fiber. Cheers.
It appears we were on similar devices, I typed most of my reply from my phone, which actually likely made my answer worse since I didn't dig too much into the research about the modules you mentioned, and incorrectly assumed they were the typical sort of laser engraver single-diode setups most people are looking into - having looked at the Optlaser unit and FAP800 briefly, let me say that:
A) they do look good, and their power ratings have a good chance of being accurate as stated
B) Your price range and the advanced level of tech you're looking to implement are on a totally different level than I incorrectly assumed!

That second point is really good, because it gives you a whole lot of options. The high power of those units helps to offset some of the weaknesses of multi-diode systems (i.e. losses from beam combination, multimode etc.) by just blasting through it with raw power. Just typing that made me smile :)

Since you're looking into this kind of high-end stuff, I'd say right now the comparison you need to make is between raw power and ease of use. Just looking at it superficially, the Optlaser unit appears to be specifically designed for CNC applications, and I think it even has the pressurized air feature I mentioned built right in. I think the driver also comes built into the unit (or at least their website also sells drivers) that I would assume are made for CNC, simplifying setup. On the other hand, the FAP800 is offered in higher power variants, but driving it might be harder. I actually use Coherent lasers all the time at work, one of my microscopes has a whole bank of them, but the driver circuitry there is highly integrated into the rest of the device, so I'm not sure how easy it would be to find/make an appropriate driver with the type of control you want for CNC. Then again, there might be a whole community out there for that type of laser, sourcing drivers and giving advice.

Best of luck finding out more, thanks for putting up with my ramblings! Hopefully some of the non-pertinent stuff in there will be helpful to someone who comes across it!

Cheers,
LM
 

WizardG

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About the 7 watts you're currently using. 7 watts out the front end implies a NUBM44 diode and suggests no beam correction. I'm using the same diode on my wife's fabric cutter. And yeah, it mostly works. The hardest thing I've found to cut is heavy polyester fabric. Even with the laser maxxed out it tends to leave a melt line in the fabric instead of a clean cut.

I had decent results with a BDR-209 single mode diode. Only 10% of the power of the NUBM44 but concentrated into a much smaller dot. It would go through pretty heavy silk at over 40 IPM. I tried to get a little more power and that one went LED. (Cutting silk with a laser requires REALLY GOOD ventilation!)

I'm going to try one of the new Sharp 1.1 watt 405nm diodes next. Decent power and much better divergence than the NUBM44.
 

RedCowboy

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The beam guality of a CO2 is hard to beat and a lot more power as well.
 

WizardG

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The beam guality of a CO2 is hard to beat and a lot more power as well.
True that. But if I find the need for more power for my rig I'd probably go with a FAP. It could sit next to the cutting machine with just the fiber running to the cutting head.

My toy originally used a steel blade to do the cutting. The diode (or potentially the business end of a fiber optic bundle) are small enough to just socket right into the knife holder. The thing is pretty much just a glorified plotter.
 
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True that. But if I find the need for more power for my rig I'd probably go with a FAP. It could sit next to the cutting machine with just the fiber running to the cutting head.

My toy originally used a steel blade to do the cutting. The diode (or potentially the business end of a fiber optic bundle) are small enough to just socket right into the knife holder. The thing is pretty much just a glorified plotter.
True, the main confounding factor I can see with the FAP unit is that unless there's a community out there like ours but for CNC laser fiber heads, it might be a complicated DIY project. I've seen a few pictures of people with that sort of setup, but the laser head portion that the fiber fed into had a distinctly homemade look. It's definitely possible that there are small scale sellers or perhaps building them is actually quite easy, I just don't know. Do you have experience with driving integrated fiber coupled laser arrays like that with power modulation? I really don't know anything about it. I'm sure there are OEM solutions, but like I mentioned with the Coherent lasers I use, the driver circuitry was really integrated and application specific. From the spec sheet Coherent provides for the FAP800, the current limits of the 30 Watt units are listed as <46A @ <~2V (and even higher currents for the more powerful units) so the diodes are almost certainly electrically parallel unless there is some serious power conversion circuitry going on inside the module which doesn't make a lot of sense to me. That kind of current draw would likely make building a driver to deliver variable, clean power difficult, which is to say that the commercial solutions are probably very specialized...of course I could be wrong and there may be accessible driving solutions out there, which would be really great news for this project. If it works out, I might have to look into some fiber coupled lasers myself!

Cheers,
LM
 

WizardG

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I haven't worked with FAP packages before but I've built a couple diode bar drivers. If you don't need analog power control I'd start with a 3.3V PS and a big MOSFET for switching. Add a few components to clean up any transients, and a big resistor as the current limiting element in the system, and for about $100 you'd have a functional driver. Not the most efficient way to do it, but cheap and effective.
 




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