Which laser for laser cutting

Google has found various sites for me with information about DIY laser cutters but they all major on the mechanical arrangements. I haven't managed to find anything which says "this is the sort of laser you need and this is how you use it"

I wonder if any of the Forum members has a link to suitable information. I get the impression from this Thread that @Grumpy_Mike may know a bit about it.

As far as I can see it should be possible to cut paper and card with a 300mW or 500mW laser - I am not interested (yet?) in anything in the 10s of watts.

Thanks.

...R

As far as I can see it should be possible to cut paper and card with a 300mW or 500mW laser

Possibly, but a lot depends on the colour of the paper.

A lot of DIY laser engravers (cutters is too much) use lasers harvested from CD and DVD writers.
However there are many restrictions on lasers in various countries and this makes specifying something everyone can get difficult.

It is a bit of a mine field. I used to be a safety officer for the lasers at my university about 20 years ago and the restrictions were harsh. Have a look at this:-

Most people seem to get component parts on eBay but that can be hit and miss.

But there is no doubt about it they are dangerous and making things "not easy for beginners" is not always a bad thing.

https://www.kickstarter.com/projects/mrbeam/mr-beam-a-portable-laser-cutter-and-engraver-kit

this link has a list of what they cut.

https://www.kickstarter.com/projects/1537608281/lazerblade-the-affordable-laser-cutter-engraver?ref=discovery

second offer, also shows what they cut.

Grumpy_Mike:
Most people seem to get component parts on eBay but that can be hit and miss.

But there is no doubt about it they are dangerous and making things "not easy for beginners" is not always a bad thing.

Thanks for the safety link. I have bookmarked it. However I was rather surprised that it has nothing to say about the ameliorating (or otherwise) effects of reflection from diffuse surfaces. Frankly I am very nervous of the dangers of lasers, including those used willy-nilly in supermarket checkouts.

I found one slightly affordable device on RS Components' website and I'm guessing from what was on the datasheet that the usual way to use them is to fire them with short pulses at the maximum permitted current rather than to light them continuously at a lower current.

...R

I was rather surprised that it has nothing to say about the ameliorating (or otherwise) effects of reflection from diffuse surfaces.

That is what your glasses are for. Reflection is an important safety measure but there is not much you can do about that in regulations, you just have to be aware of it. Most of the time in the optics labs the background is black, it is only the other equipment you have to worry about.

Frankly I am very nervous of the dangers of lasers, including those used willy-nilly in supermarket checkouts.

Those are scanning so they never stay in one spot for very long and that makes them quite safe. Remember it is not the laser light itself that is dangerous, it is the concentration or focus of the beam and length of exposure that causes the damage. The eye has good defence mechanisms if you give it a chance.

I once worked on a system that was designed to fire laser light into the eye in a raster pattern in order to take high resolution images of the retina.

have a look here this is a on going project there is mentions of places to look
http://gearotic.com/ESW/FavIcons/index.php?board=16.0

also this forum has a lot of info on lasers

Grumpy_Mike:
That is what your glasses are for. Reflection is an important safety measure but there is not much you can do about that in regulations, you just have to be aware of

I guess I did not explain myself well. I am wondering if laser light is made safe by being reflected from a diffuse surface - such as a piece of plywood. I realize it will not be safe if reflected from a shiny surface.

I guess the safest thing, and not too complicated, is to operate the laser inside a box and use a camera (e.g. a webcam) to observe what is happening.

...R

I am wondering if laser light is made safe by being reflected from a diffuse surface

Well a diffuse reflection destroys any focusing and that is what is the danger, so you can say yes, given that the laser is not ridiculously powerful like the ones they use in fusion experiments.

There's a reason why - outside of the various experiments by hobbyists and others - you don't see any low-cost semiconductor-based laser cutters or engravers.

The main reason is cost per watt.

If you start to price out what it would cost using semiconductor lasers (either monolithic or combined beam) to get the same wattage as a gas tube laser, you quickly find that gas tube lasers are much cheaper per watt - at least currently.

Furthermore, there's a question of what wavelength to use - which will effect your choice of what laser to use. As noted by Sam's Laser FAQ on Carbon Dioxide Lasers:

"Unlike the other lasers producing visible or short near-IR light, the output of a CO2 laser is medium-IR radiation at 10.6 um. At this wavelength, normal glass and plastics are opaque, and water completely absorbs the energy in the beam. The 10.6 um energy is ideal for cutting, engraving, welding, heat treating, and other industrial processing of many types of materials including (as appropriate): metals, ceramics, plastics, wood, paper, cardboard, fabric, composites, and much much more."

This is why you see such cutters and engravers use a CO2 laser tube - it's the proper tool for the job in the majority of cases.

In fact - I would highly encourage you to read the entirety of the Sam's Laser FAQ as it will likely answer all of your questions on lasers, usage, and safety.

Basically - you are likely to spend more money on trying to create a semiconductor-based laser cutter or engraver - and the results will likely be disappointing - than if you spent the money on a proper laser cutter/engraving machine.

Something you need to ask yourself is "what is my goal?" - is your goal to experiment and learn about how to build a laser cutter (even if it doesn't work or works poorly)? Or is your goal to be able to actually process materials for a project using a laser cutter?

If the former, then continue to play - just be aware that you may spend a lot of money, time, and effort - but if this is worth it for the learning experience to you, then go for it. If, however, your goal is the latter - then trying to build your own laser cutter is not likely the best choice; you would be better off spending the money on a pre-built device. There are many options available, for fairly low costs (depending on how much you plan to use them - none are really low cost if you don't plan on using them fairly often).

There's always the small and low-cost (under ~$500 USD now) Chinese laser cutter/engravers; just note that while these are low cost, then can be very finicky to get working from what I understand; here in the States, we have a company in Las Vegas (Full Spectrum Laser) that imports them, does the "re-work", then resells them at a higher price (basically making sure things work properly for the end buyer).

The next step up - while still giving a DIY option (to an extent) - is this kit - which honestly I think is the best "bang for the buck" - if you are willing to spend the time putting such a kit together.

Beyond this, you are looking at machines by companies like Universal Laser Systems - the "name brands" in laser cutting/engraving - and they have prices to match. But they do have top-quality equipment.

Something to note when it comes to laser cutters that use CO2 lasers (mainly the water-cooled tubes; the ULS systems acutally use (I believe) an RF excited tube that is air-cooled - which is a different tech) - is that the more you use the tube, the longer it's lifespan - so if you decide to go down the route of building your own laser cutter using a tube, purchase the tube last; also if you purchase a pre-made machine, use it often to get the maximum life out of the tube. In other words, tubes for CO2 lasers have a shelf-life, and they pre-maturely fail the less they are used.

Also - if your goal is materials processing - then you might also look into a CNC router; while not as fast as a laser cutter, it can typically do the same kind of work, provided you don't mind the wider kerf - that is, the width of the cut (I think of a laser cutter as a CNC router with a very small kerf).

Finally - note that whether you use a laser cutter or a CNC router - you are going to have to deal with a "mess" - in the case of a CNC router, it's a bunch of "dust" that you'll have to vacuum up and keep clean. In the case of a laser cutter - you have to deal with smoke and gasses created by the "cutting" process. You need to have some way to ventilate the machine, possibly scrubbing the gases (mainly for smell), and also deal with not letting the gasses/smoke get on the lens/mirrors of the machine (so you usually need a compressed air-source as well directing a jet of air at the exit aperture). Also with a laser cutter or engraver - never walk away from the machine while it is in operation (this especially includes homebrew builds). The material being cut or engraved can catch fire - so you need to be able to watch for that and take measures if needed, to put it out. Also - never cut PVC in a laser cutter - it'll release chlorine gas (poisonous). Never cut styrene (or foam board) - it'll easily catch fire.

I'm going to stop here - I've almost written a book. I don't have a lot of experience with laser cutters (I've only used one - a ULS 60 watt job at my local TechShop), but I have studied the heck out of things (up to and including homebrew CO2 lasers - which you want to stay away from if your goal is to make a cutting machine); ultimately, if I do get a machine of my own, it will either be one from that company in Vegas, or that kit I mentioned. But then again, my goal has been to have a machine to cut things - not to learn how to build them. Your goal(s) may be different, but you need to consider them first.

Robin2:
I guess I did not explain myself well. I am wondering if laser light is made safe by being reflected from a diffuse surface - such as a piece of plywood. I realize it will not be safe if reflected from a shiny surface.

Again - you should read the SAM's Laser FAQ if you want to really understand - but in general, diffuse surfaces are best, but don't rely on them.

Robin2:
I guess the safest thing, and not too complicated, is to operate the laser inside a box and use a camera (e.g. a webcam) to observe what is happening.

Well, that would be pretty safe - but you might have to replace the camera on a regular basis, depending on how often it's sensor gets hit (small price to pay, though).

Or - you can understand what the wavelength of the laser you are using is, and take steps to give yourself safety around it.

In the case of the CO2 IR laser tubes I mentioned before, the IR radiation is easily stopped by a simple piece of clear acrylic or glass (indeed, you can't use low-cost glass or plastic lenses to focus such a beam - when DIY'ing such a system, the biggest cost behind the laser and power supply will be the optics - they won't be cheap, a small lens about the 2 cm in diameter will run around $70.00 USD or so - for instance; the mirrors tend to be a bit cheaper).

For other wavelengths, though, you will probably need to take much different measures - the cheapest here is to get some proper certified laser-safety goggles for the wavelength of laser being used, and always wear them when operating the laser (and don't let anyone else near the system without such protective gear). Such goggles, though, don't tend to be cheap - but they are cheaper than your eyes (stay away from the "low-cost" goggles you can find on ebay - they may or may not work - and you only get one try to know). Here is one company that sells such glasses and other laser safety items:

The first thing, though, is to know (exactly) what the laser wavelength(s) you will be using are - then you can use that information to select the proper safety equipment from a place like the company above.

I’m going to stop here - I’ve almost written a book.

I really appreciate all that. It’s very interesting, and I will look at the link you provided.

If it is not simple and cheap (< £20) I doubt if I will bother. I have a small Lathe that I am putting stepper motors on, and I thought it might be a suitable platform for a small laser cutter - just to see if it can be done.

…R

Nothing to do with lasers, but, this is what I use for cutting on my CNC ( not that you asked )

If you want a real interesting project, I'd suggest a CO2 laser. I made one from scratch while I was at school (before the phrase "Health and Safety" had been invented). It's possible to make something seriously powerful and very dangerous (but not portable) with items that are easy to lay your hands on.

It takes you into other areas such as sputtering techniques to make your mirrors and growing salt chrystals to act as lenses. (glass kills the beam)

You could easily make one at home to cut through steel plate. It would only take a moments lack of attention though, to walk through the invisible beam and cut yourself in half.

I was considering building one with mirrors arranged to direct the beam over a table (cnc fashion), but doubt I'll ever get around to it. And like I say, It's very dangerous. Not just the beam itself but the high voltages used to drive it.

if you wont to do just engraving a 2w 445 diode will do if you wont to cut a co2 laser or synrad laser will do

Robin2:

Grumpy_Mike:
I guess the safest thing, and not too complicated, is to operate the laser inside a box and use a camera (e.g. a webcam) to observe what is happening.

...R

if you have a CNC motorized unit, you do not have to watch.

I thought that many plastics would be 100% safe, same as laser rated glasses. if that is the case, you only need to have such a shield to protect yourself.

LarryD:
Nothing to do with lasers, but, this is what I use for cutting on my CNC ( not that you asked )

Not what I asked in the title, but every bit as relevant.

Are those tools used while rotating at high speed or do they cut like a knife?

...R

They are high speed rotation tools.
Not the ones I use on my CNC but a hell of a lot cheaper. The ones I use cost £25 each but they will do finer cuts than those bits.

There are different kinds of nibblers for cutting thin material. One kind has a table with a die in the middle and the punch is a rod from beneath with cutting head button on top that cycles at high speed taking a nibble of material at a time. I've seen one with a pantograph that moved uncut sheets around as the original pattern rotated and the spring-loaded follower rolled along it. The speed through .030 aluminum was good and the price was low for industry.

For paper or vinyl there are X-Y tables with razor heads that turn as they move. Perhaps a small one could be made with a servo in the head and stepper motors for movement. Something that light may be able to use high strength monofilament instead of threaded rod hardware as that's what many good drafting plotters getaway with and their lines meet just fine.

There is also the Crayola Cutter (kid-safe art punch) for paper but they don't make clean cuts.

GoForSmoke:
Something that light may be able to use high strength monofilament instead of threaded rod hardware as that's what many good drafting plotters getaway with and their lines meet just fine.

I never realised this. I've got a few spare steppers hanging around. Using this type of setup I could possibly make a dirt cheep PCB printer. :slight_smile:

KenF:

GoForSmoke:
Something that light may be able to use high strength monofilament instead of threaded rod hardware as that's what many good drafting plotters getaway with and their lines meet just fine.

I never realised this. I've got a few spare steppers hanging around. Using this type of setup I could possibly make a dirt cheep PCB printer. :slight_smile:

If the movement is short enough you can do a bit better. I've seen this trick used on good floppy drives.

The head positioner stepper turned a wheel with a brass strip wound partly around. The end of the strip fed through a guide and that pushed/pulled the rod with the head on it. There was no slip or stretch.

Other than that, have you seen a sheet plotter at work? If you can find a store that sells them, they might have a display model. For all I know though, the things are obsolete.