Diy laser engraver with high power led?

So I just had a crazy idea. I'm currently doing a school project making my own laser engraver but the diodes are pretty pricey. But those 100 watt leds aren't. What if I just got one of those and a big magnifying glass to focus the light? Sorta like when you used a magnifying glass to burn leaves as a kid? Any reason this wouldn't work?

Edit: As an example of the raw output power of these, here is a video of an unfocused one burning plastic and igniting a match: [youtu.be]

Might be fun to try
but
compound lens to focus light and take the heat
may be very expensive

GSI Lumonics S003D,Industrial Laser For Cutting and WeldingTested. .S/nxx
[www.ebay.com]

may be better just to safely use a jtech photonics unit

[jtechphotonics.com]

or
something like this

1600mW 1.6W Laser Engraving Cutting Machine
[www.ebay.com]

Protect your eyes or order a white cane

... measure the size of the emitter (some square-millimeters) and then try to draw/calculate the resulting spot size, to calculate the energy density.

You'll need an energy density of roughly 1 Watt power on a spot of 0.1mm, or 100 Watts on a spot of 1mm diameter, to get the first burning/cutting effects ... I'll estimate something like a 300mm big lens in 300mm distance and a FL (focal length) of maybe 50mm (so a pretty big or strong curved lens) ... and only to get the effect of a single 1Watt-diode

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

You think the reflection off of the surface I am burning would be bright enough to damage eyes? Would simple dark glasses be enough protection?

You don't want to play games with your eyesight.
Glasses that are just dark won't tell you how much light they actually absorb where it counts.
For basically every common laser wavelength you can get the right safety glasses.
There is no real need to see the laser light itself as you will always see the result.
Either the darkening of the surface or the light caused by the burning.

Yes, the reflection is enough to cause permanent damage.

No, sunglasses are not offering any protection.

Even with correct glasses you are not supposed to look at the laser dot, they provide only protection against short accidental exposure.

Safest option is to buy a $5 Webcam, enclose the laser in a black box, and never directly look at it.

I want to add a bit:
Even if safety glasses would absorb 100% of the laser light they encounter the glasses will never filter 100% of light that has a different wavelenght.
If you cut something than the flame from that will be bright enough to cause you trouble even (or just beacause) on such a small spot.
A friend of mine was heavily into laser holograms.
His thought was "I wear the glasses so nothing to worry!".
One day while aligning his "sandpit" a loose mirror dropped down in the mounts and instead of defecting the laser it went straight into his eye.
Beam was quite powerful and almost 3mm at the mirror already so it was enough to cause permanent damage to his retina.
Most of his eyesight recover over the time of many months but he is left with a dead spot and blurry vision on the damaged eye.
And it was "only" a 2W HeNe laser with beam expander...

The answers about safety goggles confuse me a bit?! This thread is about a ( white? ) power LED being focused to one spot.
No laser safety goggles I am aware off can handle white light...

That is of course true but the important thing is laser safety - a LED is not a laser
For a white LED I would simply use welding goggles.
But if you consider the white light is actually blue light mixed with the color generated by the flouroscent covering it would be much easier to use a blue LED and to use safety glasses for blue light

Damn. OK so welding goggles? I like the idea of the webcam but it's a school project that I will have to transport to an event so a raspberry pi with a display would be the only way and that's a bit pricey. Then again, I would probably need one to send the gcode anyway unless I used an sd card which is even more hassle. Some good things to consider. Safety aside, does anyone have any comments on the viability of the led+lens idea? You can get a lens from Bang good that focuses the led into 10 degrees which is narrow enough to easily focus further using a magnifying glass(or some other lens). The other issue I see with this (although I don't know if it would even be a problem) is that because of the wide beam being focused into such a small point, as the light cuts into the material the lens will go out of focus because the distance will increase. It also means that it will be very important to balance out the platform so it's completely even. Not to mention the hassle of refocusing the lens every time you use a different thickness material. Thoughts?

My concern with LED's would be the way design itself.
A laser provides a totally different form of light too.
A LED will always have a quite wide spread for the beam of light it produces, that is defined by physics and form.
So you would first need a way to get the light really parallel as otherwise you have problems focussing it.
This means some sort of beam expander...
Just take a normal and really bright LED and a magnifying glass.
At the right distance to a wall and towards the LED the magnifying glass will give you the image of the actual crystal providing the light.
If you have steady hands you can even see the tiny wirs poking on the top of crystal.
The size of these optics define how small a parallel beam of light from there could be.
And of course you have to face the physical problems of focussing light that is combine of several different wavelengths.
The focal size is limited by the wavelenght of the light, so you would need to aim for blue or yellow or go right between them.
Either way you would not get a clean focus IMHO.

Yeah i was thinking it would be difficult to focus tighter than 1mm diameter which is pretty imprecise. What you said about the light needing to be parallel is solved by what I said in my previous post isn't it?

IMHO it would be just best to forget using a LED for it

Do some research

Wayjun 100W LED
[www.wayjun.com]

Array is 10 x 10 array of diodes (not exactly a point source)

Max output (50% above any other emitted wavelength) is around 360nm UV-A

maybe some sun screen along with welding goggles?

What is the purpose of this project?

It's just a school project. You can build whatever you want. It's an annual thing. I got the inspiration when I disassembled an Epson scanner and saw the rail+stepper+belt all in working order just begging to be used. I thought this would be a cool project until I looked at the prices of the laser modules. So I was just tossing around the idea of doing this as a cheaper alternative. Oh well. I'm thinking of doing a robotic chess board as well as it would be cheaper.

For a school project you could use old DVD burner laser LEDs. They are easy to get and cheap. A "TO18" housing is a common size for laser housings too.
Build yourself a cheap LM317 current regulated source.

I made my first baby steps ( laser wise ) with this setup and when you keep the current low, you can have lots of fun engraving cardboard or plywood.

Wow what's pretty impressive. I've seen people reuse them before but I didn't think they would be powerful enough. Dumb question but do you think it could engrave a chocolate bar/slab? Nothing like free chocolate to get the judges in a good mood...

... choclate will only melt in and around the spot, not evaporate - so you can draw a smooth line on a rough surface, but no impressive traces.

If the power will be enough to carbonize and evaporate enough, then the darker residues will become toxic ... so not such a good idea

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Viktor
--------
Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

Wasn't there a guy on Youtube doing choclate "engravings" with a CNC mill and a slightly modified soldering iron?

... a soldering iron will do a better job, as it's then more like "plowing" through the chocolate, making a good visible groove ...

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Viktor
--------
Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

The guy actually had a tip formed like a scoop on it, so the choclate would be carved out like icecreme and pushed out sideways.
Was looking quite good cosidering the tip was not rotating.