Choosing a laser for a laser cutter

[origamimavin]

Hello all. This is my first post, so let me first introduce myself (feel free to skip to another paragraph if you don't care). I'm an industrial Designer with a mechanical mind and an interest in lasers. I feel that with the right tools and the right knowledge, you can do anything. I'm currently out of stable work, so I've been working on some projects (as cheaply as possible) to broaden my capabilities and services, as well as having fun while doing it. I recently built a RepRap based 3D Printer, and since I've been craving another large project. I'm giving myself a goal of around a year from now or so to at least get started on a large laser cutter, probably about a 40W+ CO2, but I need some more income for something like that. After seeing some cheaper, lower power diode based laser cutters, I've decided to start with that. Which leads me to my planned build...

[The Build]

I've decided to use scrap electronics and make a low cost laser cutter out of it. After asking friends and family for donations, I've torn apart 2 printers, 3 scanners, and a tabletop copy machine. As a result, I have a smattering of motors (DC and stepper), linear shafts, bearings, gears, belts, screws, etc. I left some parts connected to the frames they came on if I thought it would be beneficial to do so, but just pulled apart other stuff and sorted it.

After identifying the parts and assemblies I want to use as the main base of it, I stripped off everything I didn't need. I also had to swap out some of the steppers for bipolar steppers. I ended up deciding on using the main, large scanner assembly from the top of the copy machine for the primary movement (what will end up the Y movement). Of the tabletop scanners, only one used a linear shaft (others used molded plastic and pushed against the glass for support), so I'll be using that one for the secondary movement (X movement), with the extra stability from another linear shaft pulled from something else. I've started teaching myself to code Arduino, and by connecting an Arduino Uno to a pair of EasyStepper controllers, I was able to get the steppers to move individually (based on a standalone program, but being sent commands from the computer quite yet.

I plan on using the copy machine scanner as the base of it all. I'll be putting drawer slides (harvested from the copy machine) on either side to move along with the movement. I plan on cutting apart the smaller scanner so it consists of only the motor movement, belt, and linear shafts, as well as make the carriage smaller. This will all link up with the copy machine movement and rest on the drawer slides. There will be a big piece of flat metal (or something else? MDF?) as the print surface, located above the copy machine movement, but below the smaller scanner movement (about inline with the drawer slides). This will give me a rough cutting area of about 16"x12".

[The Laser Question]

This is pretty much as far as I've gotten in terms of general planning. The next big question, which I come to you for, is the laser itself. I should mention here that I have some experience with lasers. Not a ton, but I know enough to err on the side of caution. I've made laser pointers with a red DVD burner diode and a mag light housing, and I have a Wicked Arctic 1W laser (I know, I know). I've seen people make engravers with DVD lasers, but it can't cut through much and is really slow. I plan on going with a blue diode, unless someone here can convince me otherwise. Oh, and I also plan on building something into this where it will shade the beam while it's cutting so I won't need to use glasses all the time while it's cutting, but I still will use glasses whenever I'm operating it. I've been doing some research into blue diodes, cooling them, powering them, etc. I know the capabilities of something like this is limited, but I'd hopefully like to engrave plastic, maybe cut thin plastic, cut foam, paper, card stock, and cardboard, etc. I would also hope it could move at a decent speed and not take a half hour to do a small job. Does anyone here have much experience with cutting with blue diodes? I'm thinking something between a 1-3W laser. Is going from 1 up to 3 in this case worth it? Should I get a driver with it or assemble it myself, and would it be beneficial to pulse the beam? Any input, suggestions, or links (for purchase or simply as research) would help a lot.

I should mention that I wouldn't mind doing a small build for a battery powered pointer before making a wired in, higher powered version. Possibly a smaller .5-1W pointer I could build into a small host. I'd also like to get some better glasses to use with the laser cutter, especially since I know the WL glasses are crap (which is one of the reasons I hardly ever use the Arctic indoors), so some direction on this would be go too.

Another small question (if you guys would know) is should I add any kind of Z movement? I have a couple small rack and pinion movements connected to a tiny stepper, so I could get about 3" of Z movement if I wanted. Would this extra effort benefit me at all, or should I just forget about it? How much would I be changing the height of the laser or adjusting the focus?

I'm hoping this will be a good laser project, while trying to keep this project as inexpensive as possible. I know the laser is going to be the main cost in this, but since I've only spent about $40 on parts so far (for the Arduino and EasySteppers), hopefully I can keep the whole project under around $250.

Any and all advice would be greatly appreciated!

 

[EpicHam]

Well I am no professional , and by no mean even call myself a hobbiyist of laser .
But looks like to me you'll want a 10W Co2 laser.
It provides good power for the engraving and thus ,much faster without being so powerful that it ignites the surface.

Something like this I assume.

 

[origamimavin]

Wow, that would be pretty sweet.. and fast. But I think for this build, I'm leaning more towards a diode, if at all possible. I don't want to spend what is needed for a CO2 right now, don't want to deal with liquid cooling it, and preferably not need to use mirrors to guide the beam of a stable laser. I'm hoping to mount the laser directly on the carriage pointing down.

 

[EpicHam]

Wow, that would be pretty sweet.. and fast. But I think for this build, I'm leaning more towards a diode, if at all possible. I don't want to spend what is needed for a CO2 right now, don't want to deal with liquid cooling it, and preferably not need to use mirrors to guide the beam of a stable laser. I'm hoping to mount the laser directly on the carriage pointing down.

well even with a diode ,you'll still need a dedicated cooling system.
Even at that speed of the CO2 laser , it still took them almost 2 minute to finish the marking.
With a diode churning out around max 3W, I don't think the duty cycle would be long enough to complete it.
But thats just me , perhaps the laser angels can shine some light on this

 

[norbyx]

Well first let me welcome you to te forum. I am positive that you wi find all the help you are searching for in here.

Now for what concerns the laser cutter I have no knowledge on what diode is better but I do know that a uv wavelength should be a good starting point. Or you could go to the other extreme and get a IR diode but dealing with an invisible light is not easy and very dangerous.

 

[origamimavin]

Thank you for the welcome I've been lurking around on here trying to pick up some information where I can, but thought I'd try to gi to the source directly by asking a question.

I figured the diode would need some cooling, and was thinking a heatsink, possibly with a fan blowing on it. Depending on complexity and size, I might be able to make the heatsink myself, or just design it up and have a buddy of mine that works at a machine shop cut it out of some spare material laying around. hopefully that'll cool it down enough to let it run long enough to cut or engrave for a somewhat extended amount of time. I know that taking some care early on to cool it properly will be rewarded in the long run.

I haven't thought much about going into the UV or IR ranges of lasers, other than knowing the dangers of high powered light that the eye can't see. What would you say makes them good starting points for either a project like this or a laser project in general?

 

[Things]

I'd go with a ~2W 445nm laser. Being a lower wavelength you can focus it smaller than IR, and it's the highest power visible laser you can get in diode form. It will be able to engrave wood, cut thin paper/card, maybe cut some thin plastics slowly etc

 

[origamimavin]

Thanks Things, I was hoping you might chime in (after reading some of your posts in other threads). That was about what I was expecting, but wasn't completely sure. I've seen some people making pointers that go up to as much as 3W; is that using a similar diode and just pushing it harder with more cooling, or is it a different diode? And (roughly) how much of an increase in cutting power does a 2W have over a 1W, and would there be any benefit to bringing things up to ~3W?

I'm guessing DTR's Laser Shop would be a good place to find such a diode, and I'd probably want to go with one that's fitted with a glass lens to match the output, but beyond that I'm still a little noob at knowing which diodes would be the ones to look for or which drivers to use. Despite the bump in cost, for this first time around, I'd probably be ok with getting something with the lens and driver (microboost?) already installed to better prevent me from mucking things up. Any suggestions as to which specifically might be best for this application? Maybe a 9mm?

 

[norbyx]

Well if you want power the 9mm is the solution. Diodes aren't all the same, some can be pushed more than others (of the same kind), and some will reach over 3.5W and others will top out at 3W.
My personal opinion is that if you do decide to walk down the road of a 9mm diode, you don't push it too hard. If you are using the diode for laser engraveing you will keep it on for long periods of time, and even if cooled properly, diodes (or any electronic component for that matter) will have a short lifespan if pushed over the limit.
A laser pointer has some duty cycles and most of us respect them, but even so, I am sure that they could last much more time if driven closer to their specs.

As for the driver, well there are lots of drivers that can power a 9mm diode it also depends on what will you be using as a power source (batteries, a power supply ecc.)

Check out cajunlasers.com for the one that best suits your needs. They have very fast shipping and are a trusted seller.

 

[Spooky]

Hiya,

Something like this I assume.

That's a Galvo fast because the only thing moving is the mirrors, Likely CO2 but possibly a YAG (Lamp or Diode Pumped Solid State)
Mucho expensive but great bits of kit

What would you say makes them good starting points for either a project like this or a laser project in general?

Absorption rates of materials in the IR range are pretty good, for acrylic at 1064 the absorption rate is near 100%.

does a 2W have over a 1W, and would there be any benefit to bringing things up to ~3W?

The inverse square law applies to lasers, (mostly due to detritus) double the power doesn't get double the cutting ability or speed, it's a 4/1 ratio normally. Double the power will get you somewhere about 50% extra cutting ability (speed,thickness) Same applies to increased speed, double the speed needs 4x the power to get the same or similar results. (the figures aren't exact but a pretty good benchmark)

best wishes

Dave

ps: Hiya Things

 

[origamimavin]

So after looking into this some more, it's looking like I've got the 9mm in my sights. I know when people make pointers, there's typically a small duty cycle on it, but for a project like this, I think it'll be on for some amount of time longer than that of a pointer. Is there something I can do to prevent it from dying quickly by keeping it on? I know a heatsink can help, and probably even a small fan to go with it, but is there something I should do to keep the power level better regulated to extend the life of it? I'm guessing that if I push it to the 2.5-3W range and keep it on long enough to cut and burn, it's a good way to kill the diode right quick, so is there a smaller wattage I should shoot for to extend the life of it?

 

[Things]

You're correct in that overdriving a diode will naturally shorten it's lifespan. I'm not 100% up to date on what people are driving them at safely, though I think 2W should be a good, safe level on one of the 9mm M140's. As Dave said above, you really won't notice much difference between 2W and 3W.

The first laser cutter I built, I used a 445nm diode doing around 1.4W and it could easily engrave wood and cut paper, even the slightly thicker paper card stuff.

Fan and a heatsink is good, though you need to make sure that all the heat from the module is actually making it to the heatsink. Use thermal paste etc.

 

[EpicHam]

You're correct in that overdriving a diode will naturally shorten it's lifespan. I'm not 100% up to date on what people are driving them at safely, though I think 2W should be a good, safe level on one of the 9mm M140's. As Dave said above, you really won't notice much difference between 2W and 3W.

The first laser cutter I built, I used a 445nm diode doing around 1.4W and it could easily engrave wood and cut paper, even the slightly thicker paper card stuff.

Fan and a heatsink is good, though you need to make sure that all the heat from the module is actually making it to the heatsink. Use thermal paste etc.

To be frank.. Ill say its more in the lines of charring instead of engraving, but anyway.
Just dont want him to get the wrong idea into think lasers will actually carve a groove into the surface like a milling machine.

Now , Im no expert on this , but Ill imagine you might want to check the EM absorptive spectrum of the material you intend to engrave before investing into a laser module...

Just an armchair cadet here:undecided:

 

[Things]

They can if you have a high enough power. You'd want it focused anyway, so it is possible to get a little bit of depth in wood.

 

[EpicHam]

They can if you have a high enough power. You'd want it focused anyway, so it is possible to get a little bit of depth in wood.

As long as he doesn't set it on fire and burn down his workshop :crackup:

 

[origamimavin]

Thanks for the insight, guys. I'll probably spring for the 9mm in the next week or so once some more money comes in. I can use that time to search around for the best price (any suggestions?). I can probably have a fan blowing on the surface of what's being cut to try to extinguish any flames.

I'm really looking to use this for cutting paper/cardboard, possibly vinyl stickers if I could find blank sheets, engraving some random items, but possibly most importantly, engraving into PLA plastic of things I 3D print. I'd really like to be able to print some cool, thin things, like gear boxes or whatnot, and then be able to engrave my contact info on the back of it and hand it out as business cards. Hopefully within a year or so when I (hopefully) have more income coming in, I plan on dropping some cash and building the Open Source BuildLog.net 2.X laser with a higher powered CO2 laser, which will be used for more advanced cutting and engravings of acrylic and the like for bigger projects. So this one is just something to keep me going until then, and to wet my palate to build something later with MOAR POWER!