[HN Gopher] CNC lasers for cutting and engraving
___________________________________________________________________
CNC lasers for cutting and engraving
Author : jacquesm
Score : 263 points
Date : 2024-01-26 12:17 UTC (1 days ago)
(HTM) web link (jacquesmattheij.com)
(TXT) w3m dump (jacquesmattheij.com)
| DannyBee wrote:
| 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.
| rkagerer wrote:
| 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?)
| carterschonwald wrote:
| I've been told that magnetic linear motors have much better
| accuracy.
| jacquesm wrote:
| 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.
| kragen wrote:
| 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
| ComputerGuru wrote:
| 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!
| jacquesm wrote:
| Making things in prototype form: easy. Making things
| production grade: hard. Making things economically
| production grade: super hard.
| kragen wrote:
| 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 42mm, though it might take some fiddling
| to get that to actually work. supposedly 1200x1200 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 moire pattern
| (though with a viewing angle of only 25deg 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 84mm you get a full cycle, so you get a
| transition every 21mm and you know your position
| +-10.5mm. 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 +-4mm
|
| 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
| jacquesm wrote:
| 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.
| kragen wrote:
| 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
| ComputerGuru wrote:
| 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.
| ComputerGuru wrote:
| 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
| Moire 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
| jacquesm wrote:
| 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.
| ComputerGuru wrote:
| 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!
| DannyBee wrote:
| 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
| jacquesm wrote:
| 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.
| jacquesm wrote:
| 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.
| DannyBee wrote:
| 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.
| jacquesm wrote:
| 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.
| jfoutz wrote:
| 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.
| jacquesm wrote:
| 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.
| jfoutz wrote:
| 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.
| jacquesm wrote:
| 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.
| kragen wrote:
| 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
| jacquesm wrote:
| 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!
| kragen wrote:
| 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
| jacquesm wrote:
| 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.
| kragen wrote:
| 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
| jacquesm wrote:
| 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.
| jfim wrote:
| 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.
| jacquesm wrote:
| 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.
| kragen wrote:
| i think technically it's hydrogen chloride, not chlorine,
| that makes cutting pvc hazardous
| elihu wrote:
| 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.
| jacquesm wrote:
| That's a good thing to know, I had not yet come across this
| information anywhere.
| ameminator wrote:
| 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/
| jacquesm wrote:
| I will add this link to the resources section. Thank you.
|
| edit: link added.
| double0jimb0 wrote:
| Delrin/acetal has incredible properties and is great material to
| laser cut. Make sure to ventilate, small amounts of formaldehyde
| produced.
| jacquesm wrote:
| 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/
| AdamTReineke wrote:
| 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.
| jacquesm wrote:
| 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.
| Animats wrote:
| 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.
| jacquesm wrote:
| How thick could you cut with that particular laser? Any big
| difference between white, blue and black? (I would expect
| black to the best).
| Animats wrote:
| About 3/8" stock. The limitation was focus, not power.
| jacquesm wrote:
| Ok, I've ordered a 6 mm sheet, curious if it will work at
| all and if so how well.
| 542458 wrote:
| > 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.
| sen wrote:
| 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.
| jacquesm wrote:
| 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.
| msds wrote:
| 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.
| jacquesm wrote:
| Ah yes, these are very good points. I will update the article
| accordingly, thank you.
| looofooo0 wrote:
| Fun fact: in Uni people doing stuff with not so strong white
| laser are using VR headsets with see through mode
| cenamus wrote:
| 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?
| avar wrote:
| 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.
| maxerickson wrote:
| The question is clearly about protecting the camera from
| the laser.
| looofooo0 wrote:
| Well white laser cannot be blocked with normal Kameras.
| zokier wrote:
| White laser? Rgb or something else
| jacquesm wrote:
| 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.
| cstross wrote:
| _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.
| IgorPartola wrote:
| 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.
| jacquesm wrote:
| It's in there already, even if not as the first sentence,
| but your plan is a good one.
| jacquesm wrote:
| 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.
| cyberax wrote:
| 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.
| nullc wrote:
| 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.
| rocqua wrote:
| 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.
| mitthrowaway2 wrote:
| Be aware that the safe power limit strongly depends on
| wavelength.
| elihu wrote:
| Looks like the article has been edited to cross that bit out.
| TaylorAlexander wrote:
| 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.
| jacquesm wrote:
| Oh that's great, shall I link to your project from the article?
| TaylorAlexander wrote:
| 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.
| jacquesm wrote:
| 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.
| TaylorAlexander wrote:
| 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.
| amelius wrote:
| Since it contains a high power laser: how much thought and
| money did you put into the safety aspect?
| jacquesm wrote:
| I think the video answers that question decisively!
| TaylorAlexander wrote:
| 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.
| 0xEF wrote:
| 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.
| vvvvvvvvvvvv wrote:
| 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?
| TaylorAlexander wrote:
| 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.
| cenamus wrote:
| How bad is the burned edge? I also imagine it would be
| quite different for cotton and synthetic fabrics.
|
| Amazing project!
| TaylorAlexander wrote:
| 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.
| CodeWriter23 wrote:
| The gantry sticking is likely due to the two motors moving just
| a little differently at times.
| TaylorAlexander wrote:
| 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.
| RobotToaster wrote:
| The direct drive rack and pinion system is probably
| limiting your torque too.
| TaylorAlexander wrote:
| 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.
| joshspankit wrote:
| 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?
| TaylorAlexander wrote:
| 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.
| jacquesm wrote:
| 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).
| bruce511 wrote:
| I'd be really interested in any thoughts you may have in cutting
| ceramics, like say tiles.
| jacquesm wrote:
| 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.
| kragen wrote:
| 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
| tlarkworthy wrote:
| 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
| jacquesm wrote:
| Parametric generation of SVG is a really nice tool in the box.
| That's how https://festi.info/boxes.py/ works its magic too.
| xyzzy123 wrote:
| 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.
| jacquesm wrote:
| 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.
| mattlondon wrote:
| 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?
| jacquesm wrote:
| 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.
| Ographer wrote:
| 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.
| jdietrich wrote:
| 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.
| djmips wrote:
| The LightBurn software they list in the post is a very cool piece
| of software!
| reacharavindh wrote:
| 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.
| jacquesm wrote:
| 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.
| reacharavindh wrote:
| 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.
| jdietrich wrote:
| 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/
| fmajid wrote:
| 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).
| kragen wrote:
| this is exciting, I look forward to hearing what you end up
| doing
| juggertao wrote:
| 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.
| jacquesm wrote:
| 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.
| mrgaro wrote:
| 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.
| CarRamrod wrote:
| 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.
| jacquesm wrote:
| 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.
| defrost wrote:
| 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.
| jacquesm wrote:
| 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.
| defrost wrote:
| :-)
|
| 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.
| CarRamrod wrote:
| >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.
| CarRamrod wrote:
| 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!
| jacquesm wrote:
| Sorry?
| azazel75 wrote:
| 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
| perecg wrote:
| > 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/.
| jacquesm wrote:
| Does that take the oval shape of a typical stacked laser head
| into account or does it assume a circular spot?
| perecg wrote:
| 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).
| jacquesm wrote:
| 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.
| drra wrote:
| > 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.
| CarRamrod wrote:
| Sure! In fact I'm just starting a test burn andllll'llll let
| you kn
| mobilemidget wrote:
| Is that the Macbook I put linux on for you? :)
|
| RB
| jacquesm wrote:
| 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.
| sylware wrote:
| 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).
| jdietrich wrote:
| 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
| jacquesm wrote:
| 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.
| Kosirich wrote:
| 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.
| huytersd wrote:
| What's the problem with just using existing CAD/CAM software
| and gcode?
| jacquesm wrote:
| 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.
| micwag wrote:
| 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)
| smallerfish wrote:
| 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.
| jacquesm wrote:
| If you're near me you are very welcome to come by.
| FuriouslyAdrift wrote:
| Just be sure the ventilate the area properly
|
| https://www.theregister.com/2017/01/30/berkeley_maker_couple...
| iancmceachern wrote:
| And have fire suppression and detection
| jacquesm wrote:
| 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.
| hdivider wrote:
| 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.
| the_optimist wrote:
| Well, what is it?
| codazoda wrote:
| 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(tm) 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...
| jacquesm wrote:
| 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.
| codazoda wrote:
| 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.
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