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FrozenGate by Avery
Power needed to Cut balsa wood
- Thread starter rocky79
- Start date
Actually setting things on fire is difficult, unless it has its own oxygen source. Cutting something such as wood would be extremely difficult; You can burn and score the outer surface, but then the outer layer burned, and prevents the laser from reaching further into the wood.
Cutting is also a matter of (to qoute Pseudo) irradiation not mW. An ultra precise focus could mean that a 5mW pointer could cut wood. However unrealistic wood cutting is in the first place however, I would consider a Class IIIV (>500mW) laser... First though, tell us what thickness the wood is. Regardless however, your not going to get a real clean cut...
Cutting is also a matter of (to qoute Pseudo) irradiation not mW. An ultra precise focus could mean that a 5mW pointer could cut wood. However unrealistic wood cutting is in the first place however, I would consider a Class IIIV (>500mW) laser... First though, tell us what thickness the wood is. Regardless however, your not going to get a real clean cut...
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c02 laser would do much better 
.
.CUT? Let's see... 100mW will pop a balloon, light a match etc (anything dark). 200mW will hurt your hand pretty quickly, but will have a hard time lighting a white match (if it even does). 500mW, a wild guess, would begin to get to the point of setting a white match on fire(with some help). Perhaps... You're looking at around 2000mW to do effective scarring, or wood burning, and that would be at 1mm a minute! To do wood burning alone at a regular speed as fast as you would with a hot iron, you're looking at 10000mW or more. To CUT, on the other hand... you'll probably need around 40000mw? Also, please note that this has to be a VERY thin beam with good stability and stable power. DO NOT expect to cut anything other than dark plastics with bad heat transfer abilities with a portable laser. Wood has better heat transfer than plastic, and you'll find it nearly impossible to burn it because it's such a light color that most of the laser would reflect back. I'd say you'd go VERY slowly through it at 1 Watt with a very fine point. To do such things, look into using a CO2 laser and do not expect to hold the beam. CO2 lasers use high voltage, water cooling, and are not portable. You should be able to get a machine that'll be all set and ready to do just that for you with great precision for under $2000 on eBay, like here http://search.ebay.com/search/search.dll?from=R40&_trksid=m37&satitle=laser+engraver .
Good luck;
DDL
Good luck;
DDL
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As millionaire said -- A 15 Watt CO2 focused would probably do it. Might need to pulse it to allow smoke to clear between cutting shots. The smoke might blur the focus of the beam.
I started my coffee table smoking without a lens from 5' after it burned through my beam dump
Mike
I started my coffee table smoking without a lens from 5' after it burned through my beam dump
Mike
Hemlock Mike said:As millionaire said -- A 15 Watt CO2 focused would probably do it. Might need to pulse it to allow smoke to clear between cutting shots. The smoke might blur the focus of the beam.
I started my coffee table smoking without a lens from 5' after it burned through my beam dump
Mike
Or use positive pressure through the aperture. This works by blowing clean air through the hole from which the laser is shining and it blows the smoke away in the process. You should have the cutting area well ventilated though. A nice enclosure with some CPU fans blowing outwards would do the trick
--DDL
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Evilution --
That's a reality check for sure !!! ;D
Mike
That's a reality check for sure !!! ;D
Mike
Evilution said:
OR..... a $2 scalpel.
Just because we have technology doesn't mean we have to use it.[/quote]
Does it use a laser? :-/ Where's the fun in that?? :
Have you tried cutting an 'S' shape using one of those? 
Besides... a nice set of precision gear-head linear stepper motors, a few mirrors, some good casing, and a 60W CO2 laser, all combined with some creativity and determination and a fat wallet, and you have an amazing tool that can cut down most plastics, cardboard, thin wood... etc to any shape and size you like controlled through a PC. THAT is my ultimate project.
If only I had the time and funds at the moment.--DDL
It probably be easier to buy old plotter and salvage the arm mechanism. You can rig a laser head in place of the pen, and raise the arm mechanism clearance for it to fit a bit thicker material. This way, you get less calibration, assembly, and programming works to do. This assuming that the laser head is not too heavy and not too big...
Aaaha... now someone's thinking about the same project... Allow me to share some of my ideas (they're copyrighted though )
In terms of mounting the laser, you never really want a laser to be waiving back and forth, so you never need to have a flexible power cord and such mounted on the arms. I personally think that to get the best results, you need the laser to be focused to a very fine point. So... You start off by collimating the beam exiting the diode array/tube. You guide it through a set of mirrors ingeniously placed so the beam moves wherever the arm moves. The last mirror should be the one that directs the beam down and onto a focusing lens. It is preferable to have this lens adjustable so that the beam could be focused for different material thicknesses. The beam should be exiting through a nice hole where there is a bunch of fans sucking in air from the outside and blowing them into the compartment, the positive pressure would force there to be an airflow outward clearing the smoke in the beam path. Another neat idea is to use a dichro to combine in to the IR beam a green or red laser so the user can observe the location where the beam is incident. To do that though, the machine would need a hot filter to block the IR into the machine and let the visible laser pass through. The lack of this feature only means you can't see what's happening and the whole thing can just be enclosed in a metal casing to avoid stray beams from burning a wood case. When etching a metal, you would rather have a cover to cover the filter, and preferably from the inside so that the large amounts of reflected IR wouldn't burn up the nice (and EXPENSIVE) IR-blocking glass.
Disclaimer: 60 Watts is a ton of power, and alignments should be done ONLY by a professional. A 60 watt laser will not only burn your eye, but would burn your brain behind it even! It can cut your skin and burn your clothes. It's very dangerous and requires very careful and experienced handling for proper operation.
Other than that, if anyone would like to apply these ideas in their own project (carefully), feel free to do so as long as you share your results
GL;
DDL
)In terms of mounting the laser, you never really want a laser to be waiving back and forth, so you never need to have a flexible power cord and such mounted on the arms. I personally think that to get the best results, you need the laser to be focused to a very fine point. So... You start off by collimating the beam exiting the diode array/tube. You guide it through a set of mirrors ingeniously placed so the beam moves wherever the arm moves. The last mirror should be the one that directs the beam down and onto a focusing lens. It is preferable to have this lens adjustable so that the beam could be focused for different material thicknesses. The beam should be exiting through a nice hole where there is a bunch of fans sucking in air from the outside and blowing them into the compartment, the positive pressure would force there to be an airflow outward clearing the smoke in the beam path. Another neat idea is to use a dichro to combine in to the IR beam a green or red laser so the user can observe the location where the beam is incident. To do that though, the machine would need a hot filter to block the IR into the machine and let the visible laser pass through. The lack of this feature only means you can't see what's happening and the whole thing can just be enclosed in a metal casing to avoid stray beams from burning a wood case. When etching a metal, you would rather have a cover to cover the filter, and preferably from the inside so that the large amounts of reflected IR wouldn't burn up the nice (and EXPENSIVE) IR-blocking glass.
Disclaimer: 60 Watts is a ton of power, and alignments should be done ONLY by a professional. A 60 watt laser will not only burn your eye, but would burn your brain behind it even! It can cut your skin and burn your clothes. It's very dangerous and requires very careful and experienced handling for proper operation.
Other than that, if anyone would like to apply these ideas in their own project (carefully), feel free to do so as long as you share your results
GL;
DDL
AJ_Dual
0
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Daedal said:Aaaha... now someone's thinking about the same project... Allow me to share some of my ideas (they're copyrighted though
In terms of mounting the laser, you never really want a laser to be waiving back and forth, so you never need to have a flexible power cord and such mounted on the arms. I personally think that to get the best results, you need the laser to be focused to a very fine point. So... You start off by collimating the beam exiting the diode array/tube. You guide it through a set of mirrors ingeniously placed so the beam moves wherever the arm moves. The last mirror should be the one that directs the beam down and onto a focusing lens. It is preferable to have this lens adjustable so that the beam could be focused for different material thicknesses.
I can see the rig in my mind.
One mirror at 45 degrees along the X-axis of the plotter bending the beam 90 degrees to the side, and a mirror angled 45 degrees down at the Y-axis/intersection of the plotter to aim the beam down onto the material being cut. I like the idea of keeping the laser fixed and only moving the optics. There would be all sorts of associated savings. The ability to use a more fragile laser assembly, better heat sinking/cooling, a larger heavier assembly and mounting could be used etc.
The first pitfall I see with fixed laser/moving optics is that by having the beam collimated in the fixed laser off to the side of the plotter is that the beam length is constantly changing as the plotter head moves and the optic train is constantly lengthening and shortening. So aside from desiring adjustable focus for different kinds of work and materials, wouldn't the lens need to be infinitely adjustable (or at least incrementally for each grid location, say on the inch…) as the plotter head moved about? On an XY grid, the beam travel could be anywhere from zero, to the combined distance of two sides of the work area. The second issue would be vibration of the optics/mirrors as the plotter arms move might be a problem. And thirdly, what about keeping these optics/mirrors clean?
I suppose that it would depend on the beam spec. and the tolerances required of the materials being cut. If the divergence was exceptionally low, and it was intended hobby and light commercial use, I think it wouldn't matter much. It's just that of all the X-Y plotter-type laser cutters I've ever seen on TV, none of them seemed to do it this way, the entire laser assembly always seems to be contained within the moving head, which makes me think there's pitfalls to this approach that haven't been considered yet.
How about a flexible fiber-optic conduit from the source laser to the plotter head? Then you don't have to deal with keeping moving and exposed opticsstable and clean. As far as cutting/burning applications go, most medical lasers seem to work this way.
Fiber optics was a very good idea actually. Now we don't have to deal with complicated focus, etc, and just need to concern about the vibration. Maybe there is very precise stepper motor that's moves smoothly? Even the plotter have certain degree of tolerance against vibration or the line they produce won't be straight, is it?
