Need some advice on safety

I am building a laser engraver cutter using a 445nm 2.5W diode. I am building the whole thing into an aluminum briefcase about 5" deep. Cutting area will be 12x12 inches.

The briefcase has locks (which I will be adding switches to for interlocks.) But I wanted to put a window in the top to keep an eye on progress and make sure nothing is going up in flames. This is where I need a little help.

What can I safely use for window material for something like this? I was looking at red acrylic, but of course there is no mention of wavelength protection. 445nm is UV (correct?) So would UV protection film help? A one-way mirror?

Anyway, thanks for reading. I tested the diode for less than one second just to be sure it worked and looked in the complete opposite direction and I was amazed at how bright it was. So now I am a bit paranoid about making sure this build is safe. Advice will be greatly appreciated!

P.S. On that note... how can one safely focus the lens on these without looking at the beam? I know, dumb newbie questions.

ah.. no
below 400 nm is UV
I think of a 405 laser like a mini blacklight on crystal meth.

perhaps you should just get medium priced goggles for blue lasers and just use clear plexi--NEVER even try to focus w/o them its impossible.

what lens??

AixiZ Laser here in Houston has the G2 glass lens for more mW and /or the 3 element glass for tighter focus both are about $10 each--you CANNOT use ANY plastic lens like those that come with stock AixiZ blank modules. Until just recently the G lenses were more like $40.

here are some pros you should friend MarioMaster- Swamii and Things- all are DYI CNCers or 3d modelers.
also there is a pretty active forum for CNC. For sure more member with your answers than we have here.

"Anyway, thanks for reading. I tested the diode for less than one second just to be sure it worked ..."

I hope by that you meant WHILE IN A HEATSINK--never power up a bare diode OR one w/o a properly set (mA & fv driver)

The part that holds the lens in a stock blank module is too small to mess with the focus and avoid burnt fingertips...look for an 'EZ focus knob' makers like McCrouse offer them and they make focusing much easier--also be very careful with any Teflon tape you use it.... AS can get melted onto a lens in second and that's the end of that lens.. good luck and show us some PICS!!!!

hakzaw1 said:

ah.. no
below 400 nm is UV
I think of a 405 laser like a mini blacklight on crystal meth.

perhaps you should just get medium priced goggles for blue lasers and just use clear plexi--NEVER even try to focus w/o them its impossible.

what lens??

AixiZ Laser here in Houston has the G2 glass lens for more mW and /or the 3 element glass for tighter focus both are about $10 each--you CANNOT use ANY plastic lens like those that come with stock AixiZ blank modules. Until just recently the G lenses were more like $40.

here are some pros you should friend MarioMaster- Swamii and Things- all are DYI CNCers or 3d modelers.
also there is a pretty active forum for CNC. For sure more member with your answers than we have here.

"Anyway, thanks for reading. I tested the diode for less than one second just to be sure it worked ..."

I hope by that you meant WHILE IN A HEATSINK--never power up a bare diode OR one w/o a properly set (mA & fv driver)

The part that holds the lens in a stock blank module is too small to mess with the focus and avoid burnt fingertips...look for an 'EZ focus knob' makers like McCrouse offer them and they make focusing much easier--also be very careful with any Teflon tape you use it.... AS can get melted onto a lens in second and that's the end of that lens.. good luck and show us some PICS!!!!

Click to expand...

Blacklight is UV-B isn't it? But anyway, I get your point.

Of course goggles will be used. But that doesn't mean anyone extra that happens across it will be wearing them. So, I am not really looking for something to replace the glasses, but instead to offer some level of protection.

The lens is the G2 lens. I purchased the whole laser as a kit with the G2 lens, 2W xdrive, and copper host. It is the A140 laser, which I believe I read was capable of up to 3W with a proper driver running in pulsed mode. But, I will be sticking with the stock driver.

And yes, it was in a heatsink when I tested it. I ordered the aluminum heatsinks along with the laser.

I have a 3D printer, I think I can make up an easy focus knob, unless it needs to be metal? Then I can probably machine something.

Are you saying that it is safe to focus the lens if I am wearing the goggles? Any tips beyond that? Black target? Any other precautions? I am not a fan of staring at the casted beam long enough to focus it with only goggles for protection. But maybe I am being overly paranoid.

Instead of teflon, would kapton be a better choice?

I will add some pictures of the build so far in the next post. I am just getting started, so right now, it is mostly just parts.

I have started a build thread over here: New Machine Build 2W 445nm Diode laser cutter/engraver in a suitcase

Retroplayer said:

I am building a laser engraver cutter using a 445nm 2.5W diode. I am building the whole thing into an aluminum briefcase about 5" deep. Cutting area will be 12x12 inches.

The briefcase has locks (which I will be adding switches to for interlocks.) But I wanted to put a window in the top to keep an eye on progress and make sure nothing is going up in flames. This is where I need a little help.

What can I safely use for window material for something like this? I was looking at red acrylic, but of course there is no mention of wavelength protection. 445nm is UV (correct?) So would UV protection film help? A one-way mirror?

Anyway, thanks for reading. I tested the diode for less than one second just to be sure it worked and looked in the complete opposite direction and I was amazed at how bright it was. So now I am a bit paranoid about making sure this build is safe. Advice will be greatly appreciated!

P.S. On that note... how can one safely focus the lens on these without looking at the beam? I know, dumb newbie questions.

Click to expand...

445 nm is a nice blue, not UV, and UV-B is more like 280 - 315 nm, shorter than 445 nm by a good amount.

We typically think of 10-400 nm as "UV".

Most people can't see the beam if its shorter than ~ 390 - 400 nm or so, unless the device also produces some extra frequencies that essentially act as a tracer/visible part.

Just a bit longer than the invisible UV part of the spectrum, we typically see it as purple, depending on where we start to see the spectrum (Some people see shorter wavelengths than others...but, the shortest they see is typically going to look purple to them).


Most black lights are closer to the 390 - 400 nm range, with some as short at 365 nm (currency checking, geological samples, etc), and shorter than ~ 365 nm being for further specialty applications, etc.

So, your 445 is BLUE...not UV. If you meant to type 405 nm instead of 445 nm, then its purple....still not UV yet...but closer at least.




Your safety goggles would therefore be for visible light in the 445 nm range, at least OD 4, minimum. If your source puts out extra IR too, you'd need the range to include that as well...and so forth.

If the window is also to prevent a stray reflection from ricocheting into an eye, the window should also be of the same OD, etc.

If you have goggles that are at least OD 4 and for 445 nm lasers, you can look right at the dot to focus it, if the dot is on something reflective.

If I put a 445 nm dot on something black, I can't see it to focus it...but on white, etc, I can. (With the goggles)

Hmm... since I am not sure where to find the OD rating for different plastics, or where to purchase any special purpose plastics, perhaps I need to leave the window idea out. Glasses will be worn when operating it, but there will be others around that may walk in unaware of the laser operating and there is no guarantee a reflected or refracted beam won't be looked at.

I was really hoping there was a solution, but safety comes before beauty.

Retroplayer said:

Hmm... since I am not sure where to find the OD rating for different plastics, or where to purchase any special purpose plastics, perhaps I need to leave the window idea out. Glasses will be worn when operating it, but there will be others around that may walk in unaware of the laser operating and there is no guarantee a reflected or refracted beam won't be looked at.

I was really hoping there was a solution, but safety comes before beauty.

Click to expand...

I have a 3 watt 445 nm for example, and it will light cigarettes 10' away, etc...so, as 2.5 watt is pretty close, I'd go with either no window, or, maybe a higher curtain wall assembly, or a cover you could flip back to peek in, etc, so help reduce glare to those walking in, but allow you to peer over it to see how things are cutting, etc.

The material you'd need, if wanting a laser rated window would be the plastic used to make the safety goggle lenses. (A sheet of the plastic that is rated as to its protection factor)

The ones that block 445 nm as part of their range typically look orangeish for example.

These would be an examples:

Near VIS Laser Protective Sheet Acrylic, Orange, .140" thickness

http://www.universalmedicalinc.com/...-Acrylic-Sheet-Orange-p/als-akp-12x12-umi.htm



Otherwise, you'd simply erect a curtain/wall of non-flammable flat finished/non-reflective material to block reflected light, etc....around your device, or, as a cover to peel back and take a peek wearing goggles, etc.

I happened upon a few examples of that laser safety acrylic after my last post. $200 per sq. ft. is way out of the price range of this project and not really worth it just to have a window. I am planning to change things up a bit and just have the whole thing enclosed. If I really, really want to see the progress, I will install a cheap webcam in there that can sacrifice itself instead of eyes if hit with a direct beam (which it shouldn't if mounted properly.)

For that matter, for far cheaper than a piece of that acrylic, I can buy a CCD board camera and a 2.5-7" LCD and just make a simulated window. lol

I am regretting buying a module with the driver built in. It is fixed current, so there is no way for me to adjust it down to safe(r) levels for focusing or adjusting for materials.

I just may brave myself to remove the driver and roll my own that can be adjusted.

Also, I keep reading that these should not be on for longer than a couple of minutes and then need to cool off for a long time. That is not really good for cutting/engraving. I am looking at PWM modulation now to reduce the overall on time of the laser but maintain an average constant current.

Any other tricks to work around this? And why does every video I find with these lasers show them being on for much longer than a few minutes with a skimpier heatsink than I have? Is this just crazy talk?

Retroplayer said:

I happened upon a few examples of that laser safety acrylic after my last post. $200 per sq. ft. is way out of the price range of this project and not really worth it just to have a window. I am planning to change things up a bit and just have the whole thing enclosed. If I really, really want to see the progress, I will install a cheap webcam in there that can sacrifice itself instead of eyes if hit with a direct beam (which it shouldn't if mounted properly.)

YEAH that's fer sure too Spendy. be aware that a laser can do serious damage to cameras and projectors too.

For that matter, for far cheaper than a piece of that acrylic, I can buy a CCD board camera and a 2.5-7" LCD and just make a simulated window. lol

I am regretting buying a module with the driver built in. It is fixed current, so there is no way for me to adjust it down to safe(r) levels for focusing or adjusting for materials.

I just may brave myself to remove the driver and roll my own that can be adjusted.

Also, I keep reading that these should not be on for longer than a couple of minutes and then need to cool off for a long time. That is not really good for cutting/engraving. I am looking at PWM modulation now to reduce the overall on time of the laser but maintain an average constant current.

+++That is the 'duty/rest cycling' on a decent lab laser w/ active cooling there is NO rest cycle needed- for a handheld with an 'average' size heat sink- more/longer rest cycle is needed= IF its very hot (ambient) the rest needs to be longer- Once you feel the heastsink getting warm that tells you the diode is hot-so give it a rest.
Underderiving helps for longer duty.
also there are other ways to lower the output- ND filters are one way- ONLY well cooled lasers should be used for engraving/cutting-




Any other tricks to work around this? And why does every video I find with these lasers show them being on for much longer than a few minutes with a skimpier heatsink than I have? Is this just crazy talk?

Click to expand...

They may be risking a longer over-all lifespan by doing this-and not all diodes need the same cooling- some 445s are very robust- can handle heat better. To get the smallest and best shaped 'dot' and slightly less output use the AixiZ 3 element glass lens for 400-460 nm - also I can see no reason why an EZ focus cannot be made out of non-metallic materials..

hk

Thanks for the answers, Hakzaw!

That was what I expected. I have designed my carriage to hold a 25mm fan or TEC against the heatsink in case I need it.

Also, thanks for suggesting I could do an ezfocus knob with ABS. I will give it a try. I guess the worst is that it gets hot and falls off.

I have the G-2 lens, not the three element variety. Would I be better off with the 3 element? I was thinking that too as far as smallest possible dot, so I think I already know the answer.

You may want to angle the laser so that the beam doesn't reflect right back into the laser itself. Also, a better heatsink would probably increase the longevity of your diode. That one there isn't that big and it doesn't look like you have much active cooling on it. A fan to blow away the burnt fumes would also avoid clouding the lens.

For the window, unless you have a direct beam on the window, you can probably cut those cheap red goggles and fashion a window from those and it'll be okay because of the spread. It'll be a problem if you have a direct beam off a shiny surface though.

You could also fit a webcam and that filter in the box to look around using a computer monitor. That way you avoid exposing your eyes in any way.

common concensis is the single glass lens Gs give higher power but larger spot- the AixiZ 3 element glass lens for 400-450 nm has a better spot shape-- which shold be more important to you. ATM they are about the same price at AixiZ.com (Houston)

super sdvice BB +6

Go to your local plastics shop. They will have 1/4" orange or red, transparent plastic that will attenuate the 445 laser at about OD3. I would NEVER use it for safety glasses or a direct beam, but for a scattered light cloud you should be fine.

I used take a dialed down laser with me (5-10 mW) to do tests. I scatter the light off a far wall and look at the wall spot thru the 1/8th or 1/16th sample cards they will have on a chain. The card that came the closest to zero image was the correct shade of plastic. I then buy the 1/4" thickness of what worked. I go out of my way to avoid exposing the sales guy or incoming customers. The test laser needs a button or shutter for safety. Remember Lawyers and OSHA would have a field day if you flashed a store employee.

Just don't use theatrical Gels for this, they bleach to clear on long exposures to blue/UV.

Read my online rants about home made safety glasses and their hazards via the search function.



Steve

I bought some red acrylic and have received my Eagle safety goggles, so I will try a test to see if it will work well enough for a window (of course assuming safety goggles will be used as well.)

And you and I were thinking alike about the camera. I grabbed a couple of cheap cameras and a 7" LCD for a psuedo window and already have a pair of the cheap laser goggles. If the window doesn't work, then that's an option.

As far as the heatsink. It maybe looks a bit smaller in the pic than it is. It is 19mm in diameter and 40MM long. The laser module is rather small compared to it. But, I designed the carriage to also be able to mount a 25MM fan, heatsink, or all the above and a TEC to it. I have some 25mm TECs coming from China at the moment. Need it or not, I had planned to install one. A cooler laser generates more power as I understand.

Good point about angling it slightly. But wouldn't that affect my cuts?

Finally received most of my parts, so looking to this weekend to get some assembly done and tested.

Oh, I also made up a 3D Printed focus knob with knurled edges, 32mm in diameter. I will post it up on Thingiverse once I get a chance to test it. It is in OpenScad, so parameters can be customized however you like.

I chose 32mm because it should just stick out from my carriage for easy adjustment. Probably much wider than most would want.