The better laser diode

Hi , I've read a few topics about these laser diodes but those topics were about other stuff (the color or diode vs CO2) but I'm already going to buy a diode for easier work , but I'm wondering if wattage matters more than wavelength or vice versa . For example is 300 mw 80nm better or 500 mw 808 nm . I think 80 nm NUV , near ultra violet , and 808 nm is NIR , near infra red . I've heard that less wavelength (higher frequency) is better while higher wattage is better but now these two options (808 nm 500mw and 80nm 300mw) are hard to choose from . Any ideas ?

thanks in advance .

It depends entirely on what you intend to use it for. Whatever you do be careful. These are powerful devices and, even though the light they produce is invisible, it can severely damage your eyes.

Russell.

Hi , thanks for the reply . I'll be using goggles and covering the device with a box if required . I'm going to use it for cutting 1-3 mm balsa and perhaps poly carbonate (1-2 mm).

I have great suspicions about the wavelengths you are quoting.

In my, admittedly limited, playing with diode LASERs, I have never heard of a 80nm diode. Such would be very, very, expensive, and I suspect present substantial optical hazard, at any optical power level. That aside, the better part of efficient/cheap cutters for wood are 808nm to 1024nm (in the IR range). At significantly higher cost, are the 404 to 445nm Blue/violets. require higher voltages (4.4 to 4 volts), but less touchy about lenses. The I.R. are available all over ebay for reasonablly low cost and only require about 3volts to run. Yout need a 1Watt 808nm, in a heatsinked module and a constant current regulated supply. the module needs to have glass, or ZnSe lenses (it will melt acrylic, and likely scar soda-silicon glass), at that power and above. I have cut 1/16 inch balsa and basswood, plastic cd cases, and started tissue paper fires with a 1Watt 9mm case 808nm diode LASER. Eye Protection rated for near IR is a MUST and strongly suggested at any wl).

For cutting, absorbtion wl of the subject determines feasability and /or power requirements, almost as must as thickness. most materials will absorb IR,

Thanks for the info .

Yout need a 1Watt 808nm

Isn't that a lot of power for 2-3 mm plexiglass or Balsa ?

in a heatsinked module and a constant current regulated supply. the module needs to have glass, or ZnSe lenses (it will melt acrylic, and likely scar soda-silicon glass),

Can I place the diode inside a base (I mean case and lens and stuff) that belongs to a 5mw ? Thanks in advance . EDIT : I found a 808 nm 1W but its a bit expensive for me , and it's my first cnc thing . But I found another one which was 405 nm 200 mw . Not sure if it's better than the 500 mw 808 nm but I guess more expensive = better :astonished: And another weird thing I saw is that the Blue/Purple laser goggle (200-450 , 800-2000) was green , red laser goggle was blue and green laser goggle was red ,Is that correct ?

EDIT 2 : I have made another mistake , I thought polycarbonate and plexiglass are the same (according to wiki pedia they are not) , and my main goal is cutting 1-3 mm balsa and plexiglass .

And another weird thing I saw is that the Blue/Purple laser goggle (200-450 , 800-2000) was green , red laser goggle was blue and green laser goggle was red ,Is that correct ?

If this is surprising to you, you REALLY, REALLY need to do some background reading. Otherwise, you will probably blind yourself doing experiments.

Read up on “subtractive color”. The apparent color of laser protection eyewear is completely different than colors associated with the wavelengths they block.

One place to start reading about laser safety is here.

1w is a good minimum for cutting thin stuff. With 25mw ones, you can very slowly cut thin black plastic.

A 5mw laser housing is entirely insufficient for a laser 200 times more powerful.

Expensive does not mean better; it would only work like that if the only application for lasers was cutting a single material. Since people use lasers for lots of things, it's entirely possible for a useless (for cutting) laser to cost a fortune, because it's hard to make and sought after for some other purpose.

Those colors of the laser goggles are correct. If they didn't absorb the light of the color that the laser was, what good would they be?

jremington: If this is surprising to you, you REALLY, REALLY need to do some background reading. Otherwise, you will probably blind yourself doing experiments.

Read up on "subtractive color". The apparent color of laser protection eyewear is completely different than colors associated with the wavelengths they block.

One place to start reading about laser safety is here.

Thanks for the info; This isn't surprising , I just wanted to make SURE I'm getting right stuff and it isn't another website error (similar to the 80 nm laser which was SURELY 808 as it was something like 5$ if I'd change currencies)

So I guess more expensive = better rule doesn't apply to these as it does to most things :D

DrAzzy: 1w is a good minimum for cutting thin stuff. With 25mw ones, you can very slowly cut thin black plastic.

A 5mw laser housing is entirely insufficient for a laser 200 times more powerful.

Expensive does not mean better; it would only work like that if the only application for lasers was cutting a single material. Since people use lasers for lots of things, it's entirely possible for a useless (for cutting) laser to cost a fortune, because it's hard to make and sought after for some other purpose.

Those colors of the laser goggles are correct. If they didn't absorb the light of the color that the laser was, what good would they be?

Thanks for the info; I guess thin plastic is less than a mm , so if 25mw can do that , I think the 405 nm 200 mw is enough for cutting plexiglass at 1-3mm ? I guess balsa isn't hard because some guy made a little cnc with a diode from a dvd writer and it could engrave balsa , maybe these ones could cut it ?

what matters most is being able to cut 1-3 mm of plexiglass , someone told me I need 1000mw 808 nm Is that the minimum ? Thanks

The fact that you are asking these questions indicates to me that you have a low understanding of the subjects involved (lasers, and laser cutting) - as well as proper safety. So, stop what you are doing, and get educated on the subject. If you haven’t yet - consult the following source for the best information:

http://www.repairfaq.org/sam/lasersam.htm

You might also do well to visit some of the various other laser forums, and laser cutting forums (mainly in the various CNC forums out there). That said, forums should not be relied upon for absolute accurate information, especially when high-power lasers are involved. Always double check and verify the information you are getting, including what I am telling you here!

Something to realize about true laser cutters: They work not by melting or burning the material - but by vaporizing the material with high energy; the disappation of this energy can cause the material to burn or melt, but that is generally controlled by using multiple passes and/or increasing the speed of the cut, as needed.

Those low-wattage laser diodes have a couple of things going against them - first, they are too low in wattage to vaporize anything but the thinnest of materials (usually flat-black thin plastic or paper), and they are not in the right wavelength to cut common materials used by laser cutters. That isn’t to say they can’t work in some fashion - they just won’t be very efficient; to cut thicker materials, you will need to make more passes and/or slow the rate of the laser movement down. Even so, there will be a limit to the thickness you can cut. If these limits aren’t a concern for your current project, then “cut away!”…

Just recognize they are there.

To quickly cut the materials you are looking at will require more than a bit of energy; you will be looking at a minimum of 10-20 watts. So, to that end, buy the most wattage you can afford (and can power and keep cool). Cutting things properly also involves matching the wavelength of the laser to the material to be cut; for most materials, this will be in the far IR range - not the near IR range, or UV range of most readily available and inexpensive laser diodes. Note that once you get beyond a certain power, the wavelength matters less, depending on the material being cut (metal, for instance, can be cut using far IR wavelengths, but tends to take a buttload of power - hundreds to thousands of watts - whereas using a laser with a wavelength better suited for coupling the energy to the metal might require less power - but the reason IR is used, is because it is cheaper and easier to generate than other wavelengths for a given amount of power).

To get 10-20 watts of power at a far IR wavelength is possible using diode lasers - but it isn’t cheap - not by a longshot.

Which is why you typically see low-to-medium cost hobby and commercial laser cutters using CO2 lasers (either using high-voltage discharge with water cooling, one of the cheapest methods - or RF pumping with air or water cooling, which is more expensive, but has certain other advantages that make it attractive) - because they are inexpensive to manufacture and operate, and they output relatively high power without being overly exotic in how they can do it. Even for metal cutting, you will see CO2 lasers used because they are inexpensive and scale well - but such lasers typically have to be much more powerful than other laser technologies or output wavelengths for the same job. CO2 lasers are also a well understood and mature technology in manufacturing, which also translates into keeping costs lower.

There are a few downsides to CO2 lasers, though. The two big ones are tube life, and optics. Tube life is more of a problem in low-cost sealed-tube water-cooled laser tubes. This is because in order for the tube to last the longest, the CO2 gas inside it must circulate past a special piece that “reforms” the CO2. It’s a particular kind of metal (IIRC) that does this. When the tube is in operation, the CO2 gas is changed slightly - it moving past the reformer (via convection) changes most of it back to CO2. If this doesn’t occur, the tube gets “poisoned” - shortening the life of the tube, and eventually stopping its output. It leads to the paradoxical situation where, if you want to get the most life out of such a tube, you need to use it as often and long as possible. Its also why if you are replacing such a tube, you never purchase it until you are ready to use it, because if you let it sit in the box so to speak, it will actually decrease in lifespan - ie, such tubes have a “shelf life”.

Continuous flow tubes don’t have this problem - these are tubes which have a supply of CO2 gas (actually - all CO2 tubes use a gas mixture, they typically do not use pure CO2) at one end, and a vacuum pump at the other end, continuously running a flow of gas through the tube while it is in operation. While this makes for a design that doesn’t need tube changes nearly as frequent, you now have to add a consumable to the list (the CO2 mix) - which isn’t very cheap (for high-quality certified mixes).

Finally - the reason far IR is preferred for most materials is that most materials absorb far IR wavelengths very efficiently (with the exception of shiny surfaces, metals, and most glass); by doing so, they are able to couple the energy to the material very efficiently making for fast and complete vaporization of the material possible. This has the other downside, though, of meaning that mirrors and lenses (the optics) need to be made of special ($$$) materials to reflect and refract the far IR properly; ordinary glass and plastic lenses absorb the energy fairly effectively (which is why you can cut clear plastic, and etch clear glass).

In short - educate yourself more on the subject and buy the most wattage you can afford - and far IR for most laser cutting is what you want to use, the cheapest source of which is a laser tube, and not a solid-state device (but prices of such devices are rapidly coming down).

I’m going to use it for cutting 1-3 mm balsa and perhaps poly carbonate (1-2 mm).

Perhaps the below might be the best solution for you.

cr0sh: In short - educate yourself...

Hi and thanks for the info . Well I'm not sure if I can afford/find a CO2 and I might not even be able to fit the required cooling systems and lenses and focus stuff and ..... In the little machine I'm building . I read some charts that said Plexiglass MC (the common form) transmits ~32% of 400-450 nm UV . And CLEAR plexiglass (idk what's that) transmit 90%+ at around 700-1000 nm IR. the page Going rounds and rounds to cut doesnt matter as my workspace is 15x15 and time doesnt matter. I asked my question in #LINUXCNC on irc and someone said 808nm (500mw) is better but none is generally good(aware of them not being good) Thanks another edit :: I asked this question somewhere else and they said that 1w isnt enough (is that even right ?) and I thought about using a spindle . It'd be cheaper for more power . Like , a KV 930 (930 rpm/v) and his 40a ESC costs the same as the 1w 808nm with his goggles . so which one do you think is better (more powerful) ? And how powerful should my axis be to push the spindle ? I've heard that i these cases , high RPM deletes the need for more power (like in a drill) .

Arman5592: And how powerful should my axis be to push the spindle ? I've heard that i these cases , high RPM deletes the need for more power (like in a drill) .

The power required depends entirely on the friction in the mechanical movement, the mass, and the acceleration you require. There is no cutting force with a laser cutter, unlike a router or mill. Having said that perhaps you should consider building a small cnc router instead??

If the force for movement remains the same the power required will be proportional to the speed. The rpm of the motor is not relevant.

Russell.

russellz: The power required depends entirely on the friction in the mechanical movement, the mass, and the acceleration you require. There is no cutting force with a laser cutter, unlike a router or mill. Having said that perhaps you should consider building a small cnc router instead??

If the force for movement remains the same the power required will be proportional to the speed. The rpm of the motor is not relevant.

Russell.

I guess I'm going to build a little router , easier than co2 lasers and cheaper than diode lasers but I'm not sure how powerful should my motors be , the spindle itself , and the steppers . they should be more powerful if I want to build a router (?) I've considered a brushless with 930 rpm/v and a 40a ESC but I'd be glad if It could be done cheaper . Even my laser cnc idea was a little cnc , 15x15 cm workspace .

Arman5592:
I have made another mistake , I thought polycarbonate and plexiglass are the same (according to wiki pedia they are not)

Plexiglas (one “S”) or Lucite are trade names for acrylic. Lexan is a trade name for polycarbonate.

If you’re buying acrylic in a local store you’re usually getting the extruded type (vs. cast). That might be the source of why someone told you it was different than “acrylic” – and there are certainly many types of acrylic out there.

“Acrylic” is an adjective not a noun! It is used to describe a family of acrylic plastics such as polyacrylonitrile, polymethyl methacrylate, and polymethyl acrylate all of which have different properties so you do have to be careful using the word incorrectly. If you use one of the trade names you are getting a specific formulation.

Russell.

Arman5592: I guess I'm going to build a little router , easier than co2 lasers and cheaper than diode lasers but I'm not sure how powerful should my motors be , the spindle itself , and the steppers . they should be more powerful if I want to build a router (?) I've considered a brushless with 930 rpm/v and a 40a ESC but I'd be glad if It could be done cheaper .

I have converted a small Chinese mill to cnc and have two spindles, the original 500 W 100 - 2500 rpm motor for cutting metals and a Proxxon IBS/E 100W 5,000 - 20,000 rpm which is much better for wood and for engraving on brass. If you are only going to cut balsa and plastics something like the Proxxon or perhaps an outrunner motor of similar power should do. I use NEMA 23 size motors but just for balsa etc you could use something much smaller although, as I have said, it does depend on the speed and acceleration you need.

Russell

Thanks everyone my problem is solved .