CNC lasers for cutting and engraving

This talks about accuracy, which is about positioning accuracy, but not repeatability, without which accuracy is mostly worthless. They are also often giving unidirectional accuracy numbers, which doesn't account for backlash in positioning (let alone repeatability).

Think of it as (this is not perfectly right but good enough for this explanation):

unidirectional accuracy - I command a position from 0. Where am I?

bidirectional accuracy - I command a position from 0. Where am I? I command a position in the opposite direction. Where am I?

repeatability - I command a position from 0. Where am I? I command us back to zero. Where am I? Repeat. Compare results.

It is true that, given a single directional commanded position from 0, the accuracy is likely to be 0.1mm or better.

But one missing factor in whether that will be true repeatedly is not just how it is driven, but what is being driven. Is it lead screws? ball screws? gears on rack + pinion? Nothing?

If it's nothing, you will have repeatability issues, because both stepper motors alone, and stepper motors + belts, accumulate error through backlash.

It is possible to get a lot of the backlash out using the right types of belts or gearboxes or what have you.

But even at this price point, you probably want some mechanism (helical rack + pinion, ballscrew, etc) that ensures repeatability, to ensure your accuracy will be worthless.

What do you think of magnetic linear motors like the one in the new Peoploly Magneto X? Does it help achieve substantial improvements in backlash?

BTW I would have expected accuracy would be quoted from a fixed reference point, that would coalesce all the repeatability scenarios you laid out into a single 'worst case', error-does-not-exceed value. (Are you implying with low accuracy but high repeatability you could get good results that are, conceptually, simply offset by whatever margin? Or that you'll get jagged edges / artifacts / incomplete or overdone cuts at scales below the stated accuracy threshold eg. if you have a corner approached by cuts from different ends?)

I’ve been told that magnetic linear motors have much better accuracy.

In principle they do, as do servos, you'll find neither on machines like this. An industrial servo + driver (a single one) costs more than this whole rig.

I've designed CNC gear for a living and I'm aware of the way things are done in industry. I think this low cost approach opens up an entirely now domain and if you're making boxes, wooden toys and decorative pieces the accuracy requirements are much less critical than they would be if you were to make parts for aerospace or such, but nobody is going to attempt to do that using a rig like this.

i feel like if brother can make an inkjet printer for a hundred bucks that gets positioning repeatability well below 100 microns with an optical servo, laser engraver makers can do the same thing. my capacitive digital calipers cost like ten dollars and are also in that precision range. optical, magnetic, or capacitive servos don't need to cost thousands

You have no idea how much this question has been vexing me! I gave up on the development of a public good product because I couldn’t answer that very question (low cost braille reader). I couldn’t get it to work seamlessly without high precision and couldn’t achieve high precision at low cost. Bought a couple of cheap inkjets and stripped them for parts, found proprietary optical strips and encoders, but still couldn’t figure out how they managed to machine/manufacture the plastic/nylon/POM parts to such high precision and still make a profit. In the end, I surmised they don't make a profit off the parts (though selling at a loss is illegal in the EU?) and rely on the cartridges to make money, but the bigger part of the equation is that they probably have those parts manufactured in massive numbers and with highly tuned and optimized designs carefully matched to the manufacturing process and the application.

I even put out ads trying to hire someone that’s worked as an (electro)mechanical engineer at an inkjet company to hire on a contract basis but got no responses. It’s possible those are mainly outsourced - or that the know how turned into domain knowledge that can’t be reproduced these days!

i don't think the nylon and delrin parts have to be high precision; the way i see it, all that matters is that the displacement between the optical sensor and the print head is constant and that the plastic tape isn't stretched so far that the printed page looks wrong, and that the print head stays more or less the same height off the paper and, more importantly, exactly the same angle

backlash, variable friction, motor power variation due to voltage, belt stretch, most flexions of the frame — all of that should just be 'external disturbances' that the negative feedback system automatically corrects. only the position feedback itself (and the time of actuation of the inkjets) has to be precise, that's the magic of negative feedback

as for the optical strips and encoders, i figured that a 600dpi laser printer printing on laser printer transparency film should be able to print a light/dark transition every 42μm, though it might take some fiddling to get that to actually work. supposedly 1200×1200 dpi laser printers also exist on the market for US$300. the standard way inkjet printers do this seems to be with a slit that's only slightly wider than the size of a single stripe, but a second transparency with the same 50% black pattern would also work, producing a moiré pattern (though with a viewing angle of only 25° or so due to the thicknesses of the transparent films). let me know if this is unclear, i'll make an animation or something

with a quadrature cycle (as the inkjet printer sensors seem to use, according to the datasheets i've managed to find) every 84μm you get a full cycle, so you get a transition every 21μm and you know your position ±10.5μm. that's half a thou, good enough for machining a piston

if you don't truncate the brightness to one bit, though, you can measure the phase within the cycle to probably within a tenth of a cycle, so you get ±4μm

as for who did the mechanical engineering, i suspect that it's something like ten people in the world, half of them retired. dissecting printers from different decades i see an astounding degree of similarity from one decade to the next

The one exception is probably if you want to screw bolts straight in without any kind of prep work (tapping) on the hole. Then accuracy matters, too much slop and your bolt won't hold or it will strip the material, too little and you may well end up snapping the bolt, especially a thin one.

Apropos machining pistons: the bigger issue with anything that needs a reliable 'Z' dimension on any kind of cutter like this (essentially a two-dimensional device) is that that third dimension is really only well specified at the point of focus. Outside of that it is more or less conical depending on the kind of cutter and the optics in case of a laser. Waterjet, plasma and laser all have different characteristics depending on what you cut with and in case of a laser the construction of the head and the kind of optics installed. Plasma also has work hardening effects that can not be ignored.

The only economical way to accurately cut large pieces of thick material is by using a heavy gantry mill or an EDM machine. Both will still be very costly and this sort of use is probably outside of the hobby arena anyway. If you need that kind of work piece I would suggest outsourcing it.

I read your response until near the very end and was itching to replying "but EDM!" before I got to your last paragraph! I actually was lucky enough to be able to use EDM for my initial prototype and I remain absolutely confounded as to what degree of accuracy, precision, and repeatability we're able to get out of this fairly old machining technique (and one that also avoids the z-depth issues you pointed out), but it has its drawbacks. It's insanely slow (though I don't know if machines made this side of 1990 are appreciably any faster) and it's too expensive for anything other than prototyping or one-off bespoke designs, and of course there are limitations to what materials you can cut.

The only economical way to accurately cut large pieces of thick material [..]

Fortunately for most real-world applications the old maxim about size and required precision being inversely correlated tends to hold.

I was a die-hard subtractive machining zealot but I've slowly come around to appreciating 3D printers and they've made incredible strides in terms of capabilities and accuracy over the past decade. The hobbyist stuff still has some ways to go, but the exponential improvements are hard to ignore and I think it's become a viable suggestion for a lot of things were 2D machining used to reign king, at least where the end goal is to make something and not specifically to machine something.

The pairing of 3D printers and small lasercutters is like a fabbing super power. It's absolutely amazing what I can cook up in a matter of hours here on effectively 3 square meters.

But I still miss my machine shop :)

EDM is as slow as it was in the past, there have been incremental improvements but nothing that would make you go 'oh' and of course the waste in the wire is still as much a factor (and one that makes me dislike EDM but the capabilities are off the scale in terms of precision, cut depth and consistency, in machining everything has its price).

One thing that I've noticed the last couple of months is that you need to change your way of thinking about this stuff. If you 'can't make it' you need to think of what you can make and then adapt your design to that. This is far more productive than to stick to the 'proper' way of doing things. Suddenly two - admittedly - fairly crappy machines outperform my old shop in many ways. I really miss the ability that my 12 KW plasmacutter gave me in terms of cutting metal with accuracy and speed. But material hardening was a drawback as was the metal vapor and the conical kerf. By re-working some of the designs to use wood instead of metal and 3D printed parts where the 2D process isn't enough I find I can make almost anything that I could make before as long as it is for indoors use and strength isn't the main factor. Nothing beats metal and welding in that department.

Before getting a 3D printer and the laser cutter I would still cut metal, grind and weld pretty much regularly. But now it's a rarity, and I suspect that once I get the hang of high tech plastics that it will become even more so.

yeah, those inkjets always seem to use metal machine screws to hold everything together. i don't know how to tell how the screws (and, in many cases, nuts) are made but they do seem pretty precise

but i didn't mean to say that cheap inkjets contain no tight tolerances; they contain lots of tight tolerances. (the ones on the nozzles and on the traces on the integrated circuits are a lot smaller than the ones on the screws.) i meant to say that the in-operation movements of most of the parts of the printer don't have to be precise because negative feedback compensates for any errors they introduce

the printer doesn't make any screws or any holes in anything or screw in any screws, it just squirts ink onto paper, so there isn't a question of how precise the holes it makes are

Regarding your point about the two transparent strips: they'd be 180⁰ out-of-phase and directly atop of one another? Or would they have an angular offset wrt one another instead? I'm just not sure how the light sensor and light source would be arranged with respect to those colaminated strips. I do get the point about the viewing angle limitations, though. (Super-cool sidebar: I just learned there are optical encoders that use either of the Moiré effect or the Lau effect to make optical encoders that can track position in two dimensions simultaneously.)

The operating principles of my original prototype [0] needed at least some degree of precision in the mechanical components because I had actual mechanically interfacing/interlocking parts, unlike a CNC/laser/inkjet where the head is effectively traveling "unobstructed" in free air (in the case of a CNC, creating its own void to "float" in as it goes along). There were two separate positions that needed to be tracked, the linear position (this discussion) and rotary position (for which a basic rotary optical encoder or a servo could be used).

The design of the prototype itself (machining issues aside) was sufficient for its time (late '00s) where it would have taken the place of a (then) $10-25k braille reader PC attachment, offering more characters while being available for orders of magnitude less but the world has changed so drastically in such a short time that I've had to rethink the design to be less of a PC attachment and more of a standalone "braille eReader" sort of thing, significantly complicating the mechanics and increasing the precision machining requirements. It would be a "page" composed of multiple such braille reader rows, belt-driven and either (somehow) individually drivable so one motor could drive all the rows or (preferably, if the optical encoder BOM costs could be driven down cheap enough) with a separate motor per row allowing for faster "page refreshes" (esp. important because it takes ~no time at all for a user to finish a line of text).

Here the complication becomes switching from internally actuated to externally actuated "braille discs" in a way that allows manipulating each "cell" sequentially with a drive head that moves from the start of line to the end — but also leaves the cells in an immobile position so they're not free floating and don't change when a user glides his or her finger over them to any degree in the y-axis (instead of purely in the x-axis). Additionally the size of the optical encoder element becomes an issue because there is simply not much room to cram things between each row of braille text.

My first thought to allow me to solve all these in one go was to mount each braille disc on an "electromagnetic clutch" of sorts, but I was left aghast at the price of those -- and none were miniature enough for my needs. I then tried to go old-school and use an arrangement of actual miniature magnets embedded into each braille disc so they would maintain their position until externally actuated with enough torque to overcome the magnetic inertia, but failed to prototype that with sufficient precision and couldn't find magnets that would hold strongly enough while being small enough to embed in a braille disc (and forget obtaining them within budget, at least at retail values).

Had (and still have) other ideas but the time/cost difficulties in prototyping and the limitations on mechanical tolerances of the available prototyping methods really put a damper on things.

[0]: https://patents.google.com/patent/US20130203022A1/en

This sounds like an extremely useful and worthwhile project, if you ever decide to pick it up again I'd be more than happy to contribute.

Thanks for the offer - I certainly would be happy to do that.

It's funny, I used to post about this on HN deliberately off and on for years and that never went anywhere at all but this chance response has led to the most fruitful conversation I've had on it here!

I've been in-and-out of machining and materials science for decades, it has come in very handy for the paid work I've done over the years but other than the windmill that I've built I feel that most of the tricks of the various trades have been wasted so if there is a worthwhile project to expend it on then I will be the one to be grateful.

The description of your machine has already made me wonder if it isn't feasible after all.

Making things in prototype form: easy. Making things production grade: hard. Making things economically production grade: super hard.

Steppers with encoders aren't that expensive. Surestep is an example. 150 bucks for a nema34 motor with plenty of torque that won't lose steps. Nema23 is like 50 bucks.

That is the middle ground that won't lose steps but isn't as powerful.

I agree linear motors are well overkill for this. They are mainly useful when you need very high acceleration, which isn't true here

The drive electronics on the budget machines have no easy way to add feedback mechanisms. So you'd somehow have to either roll your own driver electronics or do major surgery on the existing board. Since I don't actually have a feedback issue at all right now I'll just leave it as it is but if this becomes an issue I will definitely look into it. I still have a small form servo set + drivers laying around from another project so it isn't as if I'm wanting for hardware. And it would be nice to finally put that to use, even though it is probably a bit much for this machine.

I haven't encountered other happy customers of it, but for a bolt-on closed loop upgrade I'd recommend MKS SERVO42 series. It's a hobbyist type product that comes from AliExpress no enclosures or safety protections, and slots right into RAMPS driver ports. It just needs an initial calibration, no software changes needed at the host side.

That's interesting, ok, I will look into this. Thank you!

They still have backlash, but less so, it all depends on the masses of the gantry and the head and the speeds at which it moves. Whether it's a magnetic field or a belt doesn't matter that much, in principle there is some elasticity in the system and the height of the head above the gantry rails is a big factor in how much slop there is.

In practice you'll cut at speeds low enough that these things aren't an immediate issue, though when you start to cut cardboard or paper at near maximum speeds there likely will be some artifacts.

I will try to find the limits of the machine to see at what speeds these issues become apparent. Given the flimsy construction I'm amazed at how well it does, to be honest I had not expected it to be as immediately usable as it is.

Cutting 18 mm plywood with a < 0.5 mm kerf and < 0.1 mm repeat accuracy - especially compared to all of the other tools I have access to - is incredibly precise. In metal it wouldn't be all that impressive, but that's not what this thing is intended to do.

Anyway, the article wasn't intended as a treatment on CNC accuracy issues, there are many more that the GP hasn't touched on (such as: positioning errors due to temperature variation, which with aluminum frames can be considerable, and frames being out-of-true).

It's a dancing pig: it dances, that's the amazing thing, how it holds up compared to industrial machines that cost 400x as much isn't all that relevant.

I do think repeatability is very important. If you try to cut a circle and it ends up not even close to because you can't circle around a point twice without it being close to the same circle, ....

The rest i mostly agree with except maybe the 400x number. Seems high to get to a better level.

For the price point the repeatability is uncanny. Of course this machine is still reasonably fresh so we'll see how it holds up over time but on 10 complete passes over a work piece that spans 80% or so of the total work surface the last cut is dead on on top of the first.

I'm actually quite surprised at this, I did not expect that to be the case. But: this is my first laser (previous CNC tooling: Lathe, Mill, plasmacutter, the latter a homebrew affair at 8x4') and the main advantage that it seems to have over the other tools that I worked with is that the gantry and the head are fairly light in comparison to what you would normally expect. Even a plasmacutter requires a movable Z in order to compensate for warp (or you will definitely have material strikes).

So the head is probably < 1 Kg all together and the gantry < 10. This most likely is the biggest factor in how with such a light and - bluntly - flimsy drive mechanism it works as well as it does. It's got less backpressure than a pen plotter would have, basically just the rolling resistance of the rollers and the drag from the airhose and a thin electrical cable. I did add a segmented chain for the main gantry to ensure the cables and hose can never get tangled.

As for the 400x, an industrial laser from a brand with a good rep runs between 20 and 40K, these open frame lasers sell from anywhere between 500 and a thousand $US, I mistakenly added a zero too much so you are right about that! I spent a whole day on writing that up and was super tired, I slept a bit since and it's much better now.

These are excellent points.

I think, these are sort of problems after you "level up". Lasers and 3d printers both have pretty light toolheads and no resistance. So you can get away with being pretty half assed with your stepper control, and still get results.

You're not wrong. But there's a big mountain of stuff to learn when starting with CNC stuff. Getting a cheap machine, figuring it out, tinkering with it, improving repeatability, these things are all part of how you get better. This is sort of a hobbyist diy mindset. Even if it's not a very good machine, you can still get results out of fusion360, or scad or whatever toolchain you work through.

Now, you're absolutely right, if you've got some cash burning a hole in your pocket, you can skip a lot of that machine tinkering hassle. pro level gear is absolutely magical. I'm more of a dabbler kinda guy, try it out, learn about it, if it seems cool 10x my investment in the hobby.

Anybody who wants to turn a laser cutter into a business is going to know all the stuff you've addressed. A hobbyist, they're going to need to not die from toxic gas from tanned leather. they're going to need to work out if they want to make stuff or if they want to tinker with the machine (both are totally valid).

To be super clear, I agree with all of your points. And it would be good to indicate the suffering you'll go through with a cheap machine. But, I'd argue a cheap machine can still be really fun. It all depends on what you're after.

It's all about the work piece. If you have that kind of requirement you most likely aren't going to be making it out of wood anyway, after all wood is an organic material and things like moisture content and temperature and moisture related shrinkage and expansion are going to undo pretty much all of your efforts to achieve 100ths of mm worth of precision. It would cost a fortune and you'd end up with workpieces that are no better than what these cheap machines produce. If you were to improve on this I'd invest in a better laser head long before I'd start to worry about the final bits of precision because for that you are using the wrong material to begin with.

Woodwork to within 0.1 mm is insanely precise. You won't be making watches with this, but a mechanical clock with wooden gears is well within the realm of the possible and your accuracy will be much better than that of the best woodworker using non-CNC tooling.

I thought of an analogy a moment ago, and I want to use it.

Drag racing has a super stock category, which is pretty much a normal car you buy and then mess with. Some folks are sponsored, but generally sponsorships are in the thousands of dollars range, not the millions, like pro funny car or top fuel would have. Most of the budget comes from folk's wallets and maybe winnings.

There are race car drivers, there are race car mechanics, and sometimes they're both the same person. Any _good_ driver is going to have some idea about how to turn a wrench. Any _good_ mechanic is going to have taken a few runs, and the fear of death rules out that particular career choice.

I think your point about the material is a good one. I think, that might also be a "level 2" skill. I think there is a huge amount of stuff to do to get a real sense of what CNC can do, and what a given person is able to do with a given setup. super beginner stuff like, what do I click to make the run go? is it connected right? What's a spline? Why is the enclosure orange? Just the safety stuff alone is pretty intense. And like, engaging the safety squint isn't going to help at all.

I'm very much an advocate for getting the shitty version to learn on. Maybe I learn bad practices, but I find I REALLY appreciate good tools. I have the tools I have because I finally understood what I needed and why it needed to be that way. Some of the tools in the box rarely get touched, but they're good enough when I need them.

Sorry to ramble at you, I guess I just needed to get that out.

_edit_

and of course, you're the author of the article. Ahh, it's been a rough week. I think it's a good intro.

All of this makes perfect sense. The markets these machines unlock simply didn't exist before and suddenly you find you can have capabilities in-house that would have cost you an arm, a leg and your firstborn not all that long ago.

As for the shitty version: it actually isn't all that shitty! Of course I'd like a larger bed and of course I'd like a more powerful laser. I'd like to be able to cut through two inches of steel with zero kerf. But in practice this is what I have and the easy solution is not to pine for the tool that you can imagine but to get the most out of the tool that you can afford and that you have.

youtube channel w&m levsha seems to show success cutting some metals with a cheap laser engraver by first oxidizing the surface black, then somehow lasering it off, and repeating the process a mind-boggling number of times to cut all the way through a thin sheet. is that a thing you have tried? what obstacles did you hit?

for example in https://youtu.be/PAFBkgawH3w?t=2m10s he says he cut through a razor blade in 600 passes

Interesting, but not very practical, if I need to cut metal I'll use an appropriate tool. But on the persistence level high marks for that effort!

the advantage from my point of view is that you can cut the metal to an arbitrary shape, which no other tool can (though edm and ecm can, and in that video he mentions 'etching' as an alternative, by which i suppose he means photolithography). in this case he isn't really taking advantage of that power

Etching is remarkably precise and efficient, I've made 100's of small parts in one run, for very thin metal it would definitely be my process of choice.

EDM can do it too but it will be super slow.

yeah, and i don't have a home ecm setup yet

i think it's common for tsmc to make hundreds of billions of small parts in one run with etching

None of these cheap machines have rack + pinion or ballscrews, that's simply not available at this budget and if it is you'll end up with a machine so small that it is probably worthless. But you probably already knew that. You could retrofit it onto an existing machine but by the time you're done it would cost more than the original and the improvement would be too small to notice. While we're at it let's throw in servos and focus compensation as well as a movable Z axis... But now the machine is priced out of hobbyist territory. An aluminum open frame machine like this is not aimed at industry and so should come with lesser expectations. It doesn't even compensate for thermal expansion of the frame.

The belts are usually quite good in quality, contrary to your assertion belt drives do not accumulate backlash (though they will have some it is more or less constant as long as you don't lose steps, which normally should not happen), have a Kevlar component in them to remove a lot of the stretch issues that you'd have with cheaper belts and either the gantry is moved with two steppers or there is a cross gantry shaft which operates a passive gear (without a motor) on the other side. Obviously this isn't perfect, the shaft is long enough that it will see some torsion so when moving fast one side will lag a bit and when you come to a sudden stop you'll see some overshoot. But even at very high speeds and long series of repetitions (100's) I've yet to see any backlash or 'slop' that is visible or measurable with the tools that I currently have at my disposal. This is funny because I totally expected to find a measurable positioning error but given a nice micrometer I find the positioning error when the machine comes to a stop after many 100's of meters of travel to be < 0.1 mm and positioning error from the origin to any point on the machine to be well within the acceptable.

The thing that you will notice is that because of the open construction of the frames that the machines aren't going to be square 'out of the box', and you'll spend quite a bit of time getting them to be just so.

I don't have access to an interferometer but if I can get my hands on one for bit by borrowing one somewhere I'll do some measurements on it but for now my simple tests suffice to show that the machine is quite usable and produces output that is dimensionally accurate to the point that it makes zero sense to farm out jobs to professional laser cutting services.

If I were cutting metal (which you won't be doing with a diode laser for obvious reasons) it would be a different matter, but even there in sheet cutting the tolerances on larger work are different than they are with for instance a mill or a lathe. You won't be making any press-fit shafts with a machine like this, nor will you be cutting gears with 1 mm teeth. For that kind of work it just isn't the right tool, and lasercutting isn't the right process. If you want that kind of precision in sheetmetal you would probably either use a mill (but then your workpieces will likely be small) or you'd etch your workpiece after a photographic process to create a mask.

When working in wood, cardboard or textile the precision that these cheap machines offer is ample.

On the plus side that makes diode lasers moderately safer for use by people that haven’t been specifically trained: you can see the beam and if you can then you at least have a chance to block it.

I disagree with this. Both diode and tube lasers can instantly blind you. But diode lasers can be a pain to block - because they’re in the visible spectrum you need specialized blocking materials that are opaque in that very specific part of the visible spectrum. Worse still, many have leakage into other frequencies, making them even more difficult to block. On the flip side, a co2 tube is much simpler - some common and readily available plastics transparent to visible light are opaque to the IR wavelengths emitted by co2 tubes, dramatically simplifying blocking material selection.

You should never operate any sort of cutting laser without an enclosure and safety goggles, and it’s MUCH easier to do this for co2 lasers.

I second this; this is super bad advice. CO2 systems are comparatively safe from an eye damage perspective - unless you take a direct hit, (...don't, seriously, that's what interlocks are for...), 10.6um is strongly absorbed by your eye and you'll get superficial thermal damage, maybe cataracts or a corneal burn, but it won't get focused on to your retina so serious vision loss is unlikely. Polycarbonate safety glasses have a crazy high optical density at 10.6 and are suitable protective eyewear.

The situation for visible diode lasers is much worse. Sure, the power tends to be lower, but they're still powerful enough that looking at a diffuse reflection will result in dangerous power densities on your retina. Unfortunately, the brain is really good at hiding this sort of damage, so it's possible to not notice until it's too late.

1.064um fiber lasers are the worst of both worlds. Very high powers, invisible so you have no idea how much stray light is getting out or if you're staring at a reflection, and expensive + hard to verify safety glasses.

I like doing things with high power lasers (next up for the collection is probably a 355nm ns system?), but am glad that I had to take a lot of laser safety training before I bough my first big laser source.

Fun fact: in Uni people doing stuff with not so strong white laser are using VR headsets with see through mode

Sounds like quite a good solution actually, low latency and all. Do you know if they fitted any filter over the headset cams to protect those just in case?

Why would they need a filter? The laser light isn't making it directly to the eyeballs of the wearer.

The worst you'll get is 100% illumination on all pixels on the LCD inside the headset.

You can't stare at the Sun, but you can stare at a video of the Sun.

camera sensors are pretty easy to damage. a lot of people destroy their cameras by filming solar eclipses without taking any precaution

Yes, definitely. You will want to protect your camera sensor from a direct hit by a laser (or even an indirect one). Diffused is probably ok.

The question is clearly about protecting the camera from the laser.

Well white laser cannot be blocked with normal Kameras.

White laser? Rgb or something else

Ah yes, these are very good points. I will update the article accordingly, thank you.

Yes, you are 100% correct, my wording is sloppy and can cause danger to people operating this gear. If you can see the beam it probably is already too late! You should never get into a position where this is a possibility.

Edit: I've updated the article with a hopefully better text and a reference to your comment, if you could review it and indicate if I should make further modifications I'd be very grateful.

Please can you add a big bold warning right at the top of your article? As it is, the safety details are buried way too deep for casual readers who might be skim-reading by the time they get to it. Even a "heads up: this stuff can injure or blind you permanently if you don't follow safety procedures!" in the first paragraph would help.

A maker space I used to be a part of had a warning on our laser that said “DO NOT LOOK AT THE LASER BEAM WITH THE REMAINING EYE!” I feel like this should be the first sentence here.

It's in there already, even if not as the first sentence, but your plan is a good one.

Ok, the rewritten article is up, if you have any feedback I'd be most grateful.

Hey Charles, yes, I will do that. In fact as more and more feedback rolled in I realized that I should really lead the whole thing with a safety section, I will do some rewriting tonight.

The number of hobbyist diode laser machines that come with zero enclosure or air extraction is mind boggling. It then leads people to assume that stuff is optional. It’s not.

Yes, it is very much negligent on the part of the manufacturers, on the other hand, at that price point you should look at these as things that you can make a laser cutter from, not a complete product. For instance, my machine was after the initial build quite far out of square, it was a parallelogram rather than a square and it took quite a bit of fiddling to get it to cut square pieces. It also didn't want to stay level and that too took some work to correct.

These weren't small errors, > 2 mm in either axis across the 61 cm x 61 cm work area of the machine. But now that it has been set up properly it is quite usable.

A 'real' machine has a calibration procedure that will allow you to correct for such errors as well as a large variety of others but these cheap machines just output stepper pulses in fire-and-forget mode without any feedback at all besides the ability to re-home in case they get lost (and the homing switches are so crummy that I'm amazed they work at all). But that usually implies a ruined work piece.

From what little I know, I believe lasers up to 1mw are considered 'blink safe' in the sense that a quick enough blink response will save you from permanent damage.

Not relevant to laser cutting at those powers.

Be aware that the safe power limit strongly depends on wavelength.

Yep, IR lasers are much safer. You also have a bit of safety net because the eye won't try to automatically focus on a beam, resulting in a nice hole in your fovea.

That being said, it's also great to see the beam's location, so one possible solution is to mix in low-power red/green laser into your cutting beam. It can be as simple as gluing a strand from a fiber optic cable next to the main cutting head.

Careful with "IR" there. That's true for CO2 lasers, but ~1064nm is IR focuses fine but is quite invisible so it results in no blink or avert reflex.

Looks like the article has been edited to cross that bit out.

If anyone is interested I designed a 60 inch by 78 inch large format laser cutter that can be built for a couple hundred bucks, designed for cutting fabrics for sewing. It is an ultra low cost design, and it can be built in a way that essentially takes up no extra space in your apartment, because the gantry is removable and the bed is a thin sheet of plywood which you can cover with a rug when the system is not in use. The concept works but in my case the gantry gets a bit sticky and I lose steps, so it needs to be refined. However I have basically abandoned the project. I would love for people to use it as inspiration for future versions:

https://github.com/tlalexander/large_format_laser_cutter

I never finished making the youtube video for it, but I have a partially completed video that lacks a voiceover or proper edits for the second half. However it shows the operation of the system and offers some additional detail:

https://github.com/tlalexander/large_format_laser_cutter/iss...

Notably the design includes a built in raspberry-pi based pattern scanner which can be used to scan in clothes to make copies (with some manual work in inkscape) and can be used to scan in paper sewing patterns.

The gantry sticking is likely due to the two motors moving just a little differently at times.

Actually even with the motors disabled and moving the gantry by hand you will find spots that stick, independent of gantry misalignment (which obviously creates extra friction). The issue is that the gap between the side rails is not perfectly consistent, and the super minimal rail riding system doesn’t like this. The side rails, basically, are a little wavy.

The direct drive rack and pinion system is probably limiting your torque too.

Well and they are small steppers, because I took apart a mini delta 3D printer to reuse them. It would be a good idea to upgrade the design to use the more commonly sized 3D printer steppers.

I was thinking using 2 ball screws with one stronger motor and tying them together with timing gears and belts. But that will blow the roof off your budget.

It's a really cool project, thank you for all the work. Is there a list of fabrics it can cut? I guess no synthetics?

It will cut basically any fabric. I have used it to cut synthetics (polyester) and I've cut heavy cotton with it. The hardest materials to cut are white fabrics as they reflect a lot of light, but you can always go slower. It can take a while to cut a large white thick cotton piece though. If that was desired it would make sense to go for a slightly higher powered laser module if one was available.

How bad is the burned edge? I also imagine it would be quite different for cotton and synthetic fabrics.

Amazing project!

Thanks!

The burned edge for synthetics is itchy. You can either design the garment to hide that edge from skin contact, or design your cuts to be a bit large and then snip off the edge that would be in skin contact (beats manually tracing out the entire pattern). The burned edge for cotton is nicer.

Oh that's great, shall I link to your project from the article?

Yes please! Feel free to link to the video too, which is otherwise buried in the issues page. I do really want this project to get more exposure, but I am lead on a pretty important open source farming robot and that has taken up enough of my time that this laser cutter did not get the attention it deserves.

You probably have a bit of a fumes issue with that setup :)

Done. How is the farming robot coming along? I have not kept up the last couple of months.

Hah yes at my old apartment it was easier to leave all the doors open and wait outside until the fumes cleared (with an easy view in to check for issues), but at my new apartment fume extraction is such an issue that I have stopped using the system.

The robot is coming along! We completed a ground up redesign of the robot and it is waking up every day in the field and running test cycles on solar power. I have been refining the electronics. I got back new revs of the motherboard and motor controllers and both work well, though I already see additional changes I want to make. I designed a new steering angle sensor that dramatically simplifies the corner assembly. We are working on moving the shop closer to my house so I can go in to low volume production on prototypes. This will allow us to get long term reliability testing done! Then we would start looking at kit sales and publishing official recommended designs for those that want to make their own.

It has been a hell of a slog, so I have not produced a video in a while. Hope to get one out in 1H 2024.

Since it contains a high power laser: how much thought and money did you put into the safety aspect?

I think the video answers that question decisively!

Not a lot. If the laser module somehow broke off and pointed somewhere it would be bad, though it is not a very coherent beam actually so it wouldn't be horrible if you were watching and shut it off quickly (I did get laser safety glasses but they are cheap ones).

I did have lunch with a laser safety engineer about 20 years ago who scared the shit out of me talking about problems with blue lasers. That deterred me from ever playing with for example those big handheld laser pointers you can buy. But this module is about 30mm square and sits 5mm from the fabric, so not much light really escapes anyway. One important consideration is that there are no metal screws underneath the lasing area, so I'm not going to get dangerous reflections.

Anyway I lived alone and had no pets and I was always present while it operated. For my use I felt the safety was adequate, but obviously for something like university use it would need a full enclosure. This version is a prototype slash proof of concept.

What's scary about this question is the lack of regard to safety in most US manufacturing facilities that employ lasers. Union shops tend to be up to par with safety standards, but if you go to the smaller shops, laser cutting and engraving is often performed by an unsecured machine with broken or missing cabinet parts or optical fencing. I travel to a lot of these shops to perform repairs on a variety of equipment my employer distributes and I can't remember the last time my log didn't include notes to have sales recommend the needed safety measures for the device. This neglect to safety seems to be just accepted by the workers and met with reluctant compliant by management, with everyone pointing to how inconvenient and "unnecessary" some safety measures are.

If anyone things OSHA has a handle on this issue, they are delusional. Without a major accident happening, most of these small shops can play by their own rules simply because the body enforcing them is stretched ridiculously thin.

So, thank you for asking this. It's insane to me how many do not bother to ask.

Did you ever think about adding a camera close to the beam so that you could track cuts as registration marks and have a smaller cutting area while still being able to reposition to precisely cut out a larger whole?

Well there is a camera on the drive carriage. But no I did not think of this. It would be hard to precisely reposition the fabric because fabric distorts a lot.

There are industrial cutting tables that have rolls on both side, they leave some tabs so the material stays attached. Another trick of the trade is to cut through a stack of fabric (usually with a waterjet).

A few things with regards to safety that aren't mentioned in the article.

Get laser safety goggles that are appropriate for the wavelength of your laser, and get them from a reputable source. Always wear them whenever the machine is powered.

Make sure to have a way to easily and quickly de-energize the laser for when stuff catches on fire, be it an e-stop button or using an outlet with a switch.

And don't ever cut PVC. It'll generate chlorine gas, which will either injure/kill you or corrode your machine.

Alternatively, a machine with a proper enclosure and interlock makes the laser goggles unnecessary.

Something else I might add is don't try to cut plywood with phenolic resin. I'm not entirely sure how hazardous the fumes and residue are (probably the main risk is formaldehyde), but phenolic resin also just doesn't cut very well at all. At least, not with a CO2 laser. I'm not sure if diode lasers do better.

What seems to work well for me is to check the edge of the plywood -- if it looks like there's a thin black line between the plys, that means it's probably phenolic and it'll make a sooty mess if I try to cut it.

That's a good thing to know, I had not yet come across this information anywhere.

I haven't heard it talked about much either, it seems to be folk knowledge. Awhile back I bought a batch of the wrong kind of plywood and was having a terrible time cutting and thought it was something wrong with the machine. Eventually I stumbled on an online discussion thread about phenolic resin glues, and the plywood I bought had those thin black lines between the plys.

I found an old scrap of the plywood I had been using before and without those thin black lines and it cut fine. So, that's what I've been using ever since.

Most plywood is glued with phenolic glues whereas melamine glues will behave better with a laser: https://n-e-r-v-o-u-s.com/blog/?p=6042

I've found that plywood that comes in 4'x8' sheets usually uses phenolic glue, whereas the stuff that comes in 5'x5' squares usually doesn't. "Exterior grade" or "marine grade" anything is also a strong predictor that it uses phenolic.

This is precisely the sort of thing that I'm aiming for with this article, a collection of all those little bits of lore in one spot. It's so incredibly diffused that you spend days just reading to get started. I want to reduce that friction to a minimum to get people up and running safely.

Excellent stuff! I will update the article to add these items, one I actually thought off during the writing but forgot to include (the first) the rest I didn't think of but certainly should have. Thank you.

Edit: update the article.

i think technically it's hydrogen chloride, not chlorine, that makes cutting pvc hazardous

Delrin/acetal has incredible properties and is great material to laser cut. Make sure to ventilate, small amounts of formaldehyde produced.

Yes. I used to laser-cut Delrin using a 75W Epilog in my TechShop days. Probably the strongest plastic you can safely laser-cut.

Acrylic can be laser-cut, but polycarbonate in air, no.

How thick could you cut with that particular laser? Any big difference between white, blue and black? (I would expect black to the best).

About 3/8" stock. The limitation was focus, not power.

Ok, I've ordered a 6 mm sheet, curious if it will work at all and if so how well.

That's a material I had not thought of yet, I did try some others with unusable results, which I will document when I have a bit more time.

Ventilation is a must, I really think the manufacturers of this gear are doing their customers a disservice by suggesting that you can just use them in a dwelling.

edit: holy guacamole, that stuff is expensive!! I've found some but it is so expensive that I'll look around a bit longer to see if I can find a coupon for a test somewhere.

https://perlaplast-kunststofshop.nl/catalogsearch/result/?q=...

another local source:

https://richkunststoffen.nl/product/pom-plaat-zwart-6mm/

I'm pretty sure I recall hearing that if you cut features that are too thin in Delerin, it gets too hot and catches fire easily. I don't think you were allowed to cut it at the maker space I was at. But it's been like 7 years so I could be fuzzy on that.

That's one of the reasons I started with this article in the first place: there is so much knowledge about all of this stuff floating around but it is very fragmented. I wanted to have a single notebook for myself to keep track of what I've figured out, what works and what does not and then it seemed a natural to share it with others. Over time I intend to keep fleshing it out.

Here are some nuances that I didn't catch (admittedly, skimming) in the article based on my research and experience owning a diode laser for the last few months.

I'm not usually one to advocate buying things on Amazon, much less using filters, but in this particular case your eyesight is on the line. Unless you know a dealer of the following products that you personally trust, buy on Amazon and sort by "Avg Customer Review". And for the love of God, do your due diligence and take everything you hear about these things with a grain of salt.

First of all, the fireproof fibreglass enclosures generally work fine, but don't trust their tinted plastic windows to protect your eyes. The best practice with these things is to cultivate a habit of always, ALWAYS putting on your goggles before you ever enter the laser room.

If other adults have access to the room it's in, hang a couple pairs on the door with a warning sign to never enter without goggles. Make sure they know the rules.

Children should never, under any circumstance, enter a room containing a diode laser.

If your diode laser came with green goggles, those are almost certainly not good enough. Even if it was an expensive kit you bought. They're still the wrong ones. Look for ones with orange lenses that have video showing their lenses smoking/burning when the laser is pointed at them. And even then, make sure you have an enclosure with orange/brown tinted windows. Consider both proper goggles and the tinted window to be the absolute bare minimum in terms of eye safety.

If you bought a fibreglass enclosure and it came with a fan, it's probably too weak to do the job it needs to do. Get an inline fan that's marketed for growing weed. The diameter of the inlet and outlet ports should be smaller than that of the area within which the fan spins. The ones shaped like a can of beans almost certainly aren't going to be up to the job.

If your enclosure's design / instructions "require" the installation of a computer fan between the enclosure and the ducting adapter, you should ignore them and bolt the adapter right onto the the enclosure.

The general idea for exhausting your fumes is Enclosure->Ducting->Fan->Ducting->Exhaust Port. The exhaust port should vent outside of the building. If you own, drill baby drill and attach a permanent pest-proof vent out of which you will vent the exhaust. Otherwise buy one of the window ones.

On the subject of fans, because these enclosures are so small, make sure you buy a fan speed controller specifically designed for inline fans unless you spec out the CFM properly. You need a proper one because running large inline fans below a certain speed threshold will damage them, but on the other side of the coin, an overpowered fan is a waste of electricity at best and a safety hazard at worst. And an underpowered fan is effectively useless.

My final note for now is that there is, in fact, a method to the madness of the design of the enclosures with no bottom. Any fan worth its salt will be airtight enough to use suction to hold your enclosure down on the tabletop even with its intake window(s) open. This is a good thing - a fully enclosed fibreglass box would not allow sufficient air movement to vent fumes.

There is so, so much more to it, but in terms of safety logistics, I think that's most of the important points.

Very good stuff. I didn't buy mine on Amazon for that exact reason (I don't like Amazon and I like dealing with the manufacturers directly) so our reasoning is opposite :) I don't trust Amazon reviews and I would not like dealing with Amazon in case of an issue with the machine. Manufacturers tend to have a support track for stuff they sell directly and they don't bother much with customers that bought through Amazon.

As for the enclosure, I'm going to do a whole separate section on enclosures this is more or less a placeholder, I'm still waiting on a sheet of 2C04 Acrylic to use as the window (the transparent piece in there right now is temporary). Good point about the glasses, the ones that come with the cutters usually royally suck.

While you're making recent comments, as a tangential aside, old mice with scroll wheels make semi decent X-Y position recorders for moving surfaces that the mouse guts+scroll wheel can be sprung against so the wheel rolls as the object moves.

You will have to hack some old mouse driver code to interface and determine which USB mouse input(s) are of interest.

It's a kludge that saved me time over a long three day weekend with no shops open years back when I was putting together a laser scanner project.

Eventually we had a proper stepper moter, for proof of concept it was an "uncontrolled" motor with a mouse scroll wheel counting clicks for rough "good enough" position feedback.

That's a hilarious hack, I have a whole crate full of old mice so definitely will have to try this. Worst case it will allow you to automatically e-stop the machine if it encounters an obstruction. For instance: sometimes the air assist will flip a piece up and the laser head during high speed traversal will run into it. That requires immediate manual intervention right now, it would be nice if that happened automatically.

:-)

It was an Aha! moment for me when I looked a crate with old mice - they have rolling wheels and click buttons with plenty of sample drivers for counting wheel turns, <onclick> <clickrelease> events, etc.

Ain't pretty - but it works until a better version comes along.

Also I understand if you don't link or mention any of the (potentially critically important to your readers) information I provided you in your article because you ignored it all past the second line to virtue signal about Amazon, cheers comrade!

Sorry?

I didn't buy mine on Amazon for that exact reason (I don't like Amazon and I like dealing with the manufacturers directly) so our reasoning is opposite

...For everything?

Unless you know a dealer of the following products that you personally trust, buy on Amazon and sort by "Avg Customer Review"

The 'following products" were inline fans and goggles and enclosures. And I stand by that.

In terms of primary hardware I agree if you have a reliable manufacturer. I avoided saying "Buy a Falcon2 (22w minimum) from Creality because almost everything else is overpriced or shit" because I didn't want to ruffle feathers even though it's true.

If we could get off-the-self and cheap CNC cutters to deal with aluminum ~2-3mm plates... But I don't think it is possible.

A pain to get that DYI keyboard plate (no, I don't want to use a PCB).

Depends on your definition of "cheap", but a Shapeoko handles light cuts in aluminium very well. Cheaper routers are readily available on Aliexpress if you don't mind tinkering.

https://shop.carbide3d.com/collections/cnc-routers

I did watch some youtube video about "cheap" aluminium cutting (carbide mills), it is far from easy.

It seems plasma/high energy laser cutters are a must.

Plasma cutting aluminum has challenges all its own.

Hydrogen production for one (you can imagine where that's going :) ), and you'll need some shield gas to make it work reliably. Cutting speed is going to be pretty impressive, edge quality not so much compared to a laser.

Then we are back to high energy laser CNC cutter...

Yes, for sheet that is the best way. For complex shape it's milling for subtractive and sintering for additive.

https://www.btu.com/applications/sintered-metals/

Cheap, laser and metal cutting are not normally seen in the same sentence...

You'll want a beefy fiber laser and an industrial setup with regards to fume extraction, metal vapor isn't exactly healthy to breathe. Operating a machine of that power level in or near a residence is probably not the best idea unless you live remote. For work like that I'd probably outsource it, I do not have enough metal cutting projects that I need that capability in house and in an extreme case I can always break out the jigsaw (or even the grinder...) for a one-off. Not quite as precise but for most stuff I do that would be good enough.

if the spot size is asymmetrical, so you need to cut slower in the direction where the beam is less focused for consistent results

Some CAM software orient the trajectories so that the part is always on the same side of the trajectory (i.e. only G41 or G42 is used in a given NC file). This is what we do at https://nestandcut.com/.

Does that take the oval shape of a typical stacked laser head into account or does it assume a circular spot?

Currently we modelize a circular spot. When the machine has 5 axes the post-processor may tilt the beam axis to compensate a conic beam (especially useful in oxy-fuel cutting and water jet cutting afaik).

Just the knowledge that the spot is oval is already useful: you could compensate cutting speed to correct for that and get a more even burn.

A simple trick to check the shape of the spot is to set the beam to low power and to purposefully increase the Z as far as it will go and project the beam on a piece of black anodized aluminum. You'll very clearly see the alignment of the individual diodes and as you lower the Z you see them converge on what eventually will become the focal point. This gives you very useful hints about the shape of the cone, on my machine the cone is definitely oval (if not outright linear!) in cross section, far longer in X than in Y. This results in an ~ 30% penalty in cutting speed depending on the direction of travel. To ensure full penetration I have to set the machine 30% slower, whereas if the software compensated I'd be able to run the same speed with much more consistent kerf width as a result and less time wasted.

Interesting, do you do the speed reduction per-axis or globally ?

Unfortunately, globally because LightBurn, the software that I use doesn't allow to compensate for this. But I could run my own G-Codes or maybe patch GRBL to demonstrate the effect.

I wish the CNC machines with a router instead of the laser became more standardised, and available to buy off of AMAZON and made in a “it just works” territory.

The choices are either DIY ones off aliexpress or the more expensive ones like Shapeoko.

The Openbuilds machines are the closest thing to a "standard" in low-cost CNC routers. They are a kit, but they're well-designed and have good support.

If you want a CNC router that truly "just works", you're looking at spending five figures on something that's delivered by a semi truck. You can't escape the laws of physics, so a reliable and stable machine necessarily requires a big steel or cast iron frame.

https://openbuildspartstore.com/machine-Kits/

https://lagunatools.com/cnc/swift-series/

Inventables X-Carve is also a good option, very similar to the OpenBuilds machines but just slightly more refined and integrated.

I've had mine for years and love it.

https://www.inventables.com/products/x-carve-1

The laser cutters are usually also sold as a kit rather than assembled.

There are quite a few of these:

https://www.aliexpress.com/w/wholesale-cnc-router.html

Quality is all over the place and given the fact that they have a tool that creates backpressure (and that sometimes wants to 'climb' the workpiece depending on the direction of the cut) any kind of imperfection in the mechanism will immediately show up on the work product.

I posted a DIY one the other day that I think is pretty neat https://www.instructables.com/LOW-COST-DIY-500-CNC-MILL/ .

I don't think anything you buy of Ali or Amazon in this price range will ever be in 'it just works' territory, neither laser nor mill. They're barely functional and usually need quite a bit of tweaking to get them to work properly. And tbh I don't think the Shapeoko is that much better.

CNC milling is messy, you'll spend quite a bit of money in tooling and the work area is usually quite limited. If you want a larger machine and it still has to be affordable I'd shop around for an older industrial machine. It will be large and heavy but construction wise there isn't going to be anything small and lightweight that can begin to compete. If you're lucky you might even get a bunch of tooling with it.

Indeed. Thanks for the link to the DIY setup. A few years ago, I would have been super excited about building one like this myself even if it takes a month of tinkering to get it to do what I want. Now with two kids and _life_ the way it is, my 5 hours on Saturday is precious. I need to choose between building tooling versus building the thing I want.. As much as I resist, I’m probably the target audience for companies like Shapeoko. I just can’t pull myself over the wall to spend three thousand plus Euros on a thing that will get used on weekends in my hobby workshop :-( If it was about a thousand euros, I’d have found a way to justify it..

I see all the caveats about the lasers and also the nasty fumes they make me deal with - hence the desire to go with a mill - a known devil to me.

Also, I work most of the time with Hardwoods and CNC mill is more appropriate for the task than the laser regardless of power.

I’ll keep a look out in marktplaats for any used CNC mills. I hadn’t thought of that.

I am primarily interested in engraving metals, so I got a 18W fiber laser with a galvo head (laser is deflected by mirrors mounted on magnetic mounts like those on old analog multimeters, much faster than moving the laser head on a gantry).

this is exciting, I look forward to hearing what you end up doing

Mostly engraving tools with my name and contact info, some keychains as gifts (got cheap blanks from AliExpress). Some examples:

https://majid.info/images/reddit/laser_dog_tag.jpg

https://majid.info/images/reddit/laser_pliers.jpg

https://majid.info/images/reddit/flash_drives.jpg

https://majid.info/images/reddit/laser_coin.jpg

https://majid.info/images/laserbinos.jpg

wow, that looks fantastic! it looks like you're able to engrave deep enough to cut through thin metal; is that true? how many passes do you need? does it work on aluminum foil, or is that too reflective? how about razor blades? how big is the positioning error, like, what dpi of laser printer is the result similar to? how fast is it, and how much does it cost to run?

That's some amazing work.

So something that I just can't get past with laser cutting things is the smell. You cut e.g. a Christmas bauble and it stinks of pungent burnt wood ~forever. If there is a laser-cut bit of wood there, it's the first thing you smell as you walk in the room

Anyone have any good tricks to avoid that?

Using laser-grade ply is important, because often the smell is more glue than wood. Air assist makes a big difference, as does using a well-focussed laser source with good beam quality. Failing that, try a sealer coat of shellac or polyurethane.

You're absolutely right, I can tell whether a laser cut part is present though ~forever seems to be 'a couple of months'. Eventually the smell fades. I'm particularly sensitive to fire smell (we all are but I have my reasons for being a bit more paranoid than most) so this was a real problem initially for me.

To remedy you can oversize the part a bit and then sand off the burned edge, you can lacquer or paint it to stop the carbonized wood from escaping (though adherence of lacquer and paint is poor on the burned edge) and you can (lightly) sandblast the pieces.

Edit: I've added this to the article in the 'wood' section.

I got a trash can with a lid for all my small parts and a shop vac nearby to clean out the catch tray of the laser after I cut something smelly.

I also upgraded my exhaust fan to make sure nothing got into the room. I got a variable speed DC fan so that I can leave it on a low speed after cutting something smelly to help the smell go outside until it dissipates.

I had the most issues with smell when I was using cheap wood from home Depot. When I switched to real Baltic birch the smell wasn't as bad so I think the other stuff had chemicals in it.

Acrylic still smells bad but it dissipates quickly.

The LightBurn software they list in the post is a very cool piece of software!

Indeed, highly recommended!

At Vancouver Hack Space we recently upgraded from LaserCAD (terrible software that came with our 80W CO2 laser cutter ~10 years ago) to LightBurn. It's been a joy.

Beware some possible subtle radius compensation bugs in LightBurn, I haven't nailed it down exactly yet and when I do I'll contact them but the inside/outside detection doesn't always work with imported SVG files. This bit me quite badly and it took a while to figure out what was going wrong. Choosing 'optimize toolpath' seems to cure it for now as a workaround.

There's a Vancouver connection here. Jason Dorie, who started LightBurn is from Vancouver! You might already know that.

If you have trouble engraving tumblers, I've found a trick that works really well. The tool ensures that the laser maintains consistent focus at both edges of the tumbler resulting in a more uniform engraving. I call it The Tumbler Trick™ and I've posted instructions on how to make your own at the URL below.

https://www.tumblertrick.com/how-to-make-the-tumbler-trick-d...

Do you use a special lens for such long focus work? I don't think my machine has the depth-of-field required for engraving across more than a few mm deviation in the Z direction.

We aren't using a special lens. It works but only within a certain range. The ideal laser focus, on our machine, is only about 3mm from the lens body. The handle posts necessitate moving the laser head farther away, to around 11mm. So, we move the laser head as close as possible without hitting those posts. We don't bend the posts for fear of damaging them.

This tool helps level the cup edges the best we can. My wife makes between 25 and 100 of these cups a month and this tool really helped her. We were using a digital level and having to create a design of the cup edge and figure out the angle for each brand and size. This gets rid of that complexity.

The laser is out of focus for the majority of the burn but it's in a range that allows it to work well on powder coated tumblers.

Specifically, we use a Creality Falcon 2 Diode 22W laser for tumblers. It's not, however, the machine I would recommend to others, for a number of reasons.

Very interesting comment, ok I will abstract and put this in the engraving section, is there a set of materials and/or colors that you find work better and others that really do not?

There is a boom in this field in recent years, specifically for laser texturing using femtosecond lasers. What were 10 years back laboratory lasers are now being put on standard CNC machine gantrys.

Unfortunately, what I see lacking in high end laser CNC machine market is software and no separation between CAM programming and execution that exists for milling machines. There is no equivalent to G-code that can be generated on w/e software and then run on different machine. There are cases where this is impossible as due to the way it's done, it would quickly overload even large RAM memory capacities.

What’s the problem with just using existing CAD/CAM software and gcode?

I don't think there is a problem per-se, it's just that G-code tends to be rather static so if you're doing things like nesting and engraving of variable text going through and extra G-code conversion step can get a bit tedious.

I'm old school enough that I can program G-codes by hand (and by heart), compared to normal programming it is super simple, you can pick it up in an afternoon. But for complex graphical work the automatic conversion to G-code from a drawing tool is a real time saver. CAD/CAM software tends to export in some 2D format for laser cutting, usually either a 2D DXF file or SVG. You then convert on the fly to G-code in the laser driver software.

I'm working in the laser marking/engraving field, we actually discussed G-code internally but in the end decided against it as it was not suitable for our product. (Too many laser parameter and "dynamic" stuff like QR codes)

Lasers are so cheap these days. For $50 you can buy a DMX controlled 0.5W RGB laser from AliExpress.

I've been thinking about using them for Christmas lights.

Please don't. It's so easy to blind somebody with a laser. I always get anxious near laser shows, especially when there's a change it's not done properly as it could still blind you several hundred meters away.

That's very much not safe! I was at a resort in Eastern Europe over Christmas and on the other side of a lake someone had a rig like that. It caused me no end of trouble because it kept sweeping across the place where I was seated and this was easily a 100 meters or more. Make sure you know what/who you are pointing at.

I'd be really interested in any thoughts you may have in cutting ceramics, like say tiles.

maybe cnc sandblasting with emery will work for that, but it will produce a lot of airborne crystalline silicon dust, which causes silicosis if animals breathe it. maybe better to cut your clay to rough shape before firing and then wet grind to final dimensions after firing if necessary. hot isostatic pressing may also be an option depending on the use

Anything reflective is right out, but I have some tiles of various plumage laying around and I'll run a materials test on them. I'll post an update (this will take a few days to set up).

My first response is: wrong process, I'd use a water cutter with an abrasive added to the water for this particular application. But my second response is: you can't be sure without trying, but I predict it will either not work at all or it will take an insane number of passes.

Just be sure the ventilate the area properly

https://www.theregister.com/2017/01/30/berkeley_maker_couple...

Wow that's ugly, and yes, that's covered. And without that I consider a laser cutter to be both utterly unsafe and unusable.

Edit: I thought that was familiar:

https://news.ycombinator.com/item?id=13507734

Edit2: it turned out to be CO2 poisoning after all.

And have fire suppression and detection

Warning about pvc is good - I feel like sterner caution about leather might be warranted - e.g. veg tan leather is fine (if stinky) but most leather you see is gonna be chrome tanned and lasering it will blast heavy metal vapour / toxic dust into the air and contaminate your enclosure.

IMHO if you are a beginner you should be very careful about cutting any material that hasn't been explicitly designed to be laser safe.

Leather is really bad, I'll up the warning level on that one, thank you for the pointer.

Edit: amped up the warning on leather, also added a more general version of that warning to the heading on materials.

I love Lazer cutting because the drawing format is SVG and therefore it's very easy to to write parametric generators in the programming language of your choice! So it's very easy to connect the physical object to some larger app, like 3d visualizing the expected output or assembly instructions and remain parametric throughout.

I'me using observable notebooks to design some things https://observablehq.com/d/1117987aeab1be0d

Parametric generation of SVG is a really nice tool in the box. That's how https://festi.info/boxes.py/ works its magic too.

I'm waiting for the price to come down a little. I need to engrave 200+ plant labels for my garden, but I can't justify spending $2-3k on a machine that could handle that.

If you're near me you are very welcome to come by.

Is that the Macbook I put linux on for you? :)

Hey R, yes, it is!! It still goes strong even though the battery doesn't hold much charge any more. Quite amazing, given that it's been around the planet three times or so and it hasn't exactly been treated friendly.

Interestingly, if you're doing CNC laser cutting as a business, with the larger CO2 laser cutters, you're gonna spend a lot to keep replacing those CO2 laser tubes. Because the gas degrades with heavy use, even if the tube is intact.

Why can't you just refill the gas? Because the precise gas combination that makes for a stable, reliable laser tube was monopolized ages ago.

Because of that one trade secret, countless tubes end up in the trash and way more than necessary are manufactured. Classic case where monopolization of scientific knowledge can end in significant unnecessary waste.

Well, what is it?

Seriously: stay away from most plastics and all PVC

Could you still test it wit EVA (ethylene-vinyl acetate) foam? I use it for prop-making. While it's easy to cut with knife, CNC laser would make that stage much faster.

Sure! In fact I'm just starting a test burn andllll'llll let you kn

As a supplement to this excellent breakdown of laser cutting, can I recommend the Guerrilla Guide to CNC [0]. To this day, it's the best reference I've ever read on small volume fabrication with a CNC machine and/or 3D printer. If you enjoyed the original post, you may enjoy this as well.

[0] https://lcamtuf.coredump.cx/gcnc/

I will add this link to the resources section. Thank you.

edit: link added.

Some years ago with a friend we built a Lasersaur ( https://lasersaur.com ) from scratch. It is equipped with a 130 w CO2 laser. Amazing open source project. Unfortunately the guy that stays it abandoned the project, but there a ton of resources there