hey
So I often caught myself in putting the goggles of and adjust it, then putting them on and burn etc. But that would not make sense, doesnt it?
In the commercial and scientific world, we:
Design the laser to reduce power when aiming,
Use a aiming laser of a different wavelength
Use a attenuating aiming window.
Use a aiming camera.
Make a physical device to hold the laser at the focal point (think thin rod)
Use test samples of the working material to do the aiming.
Build a autofocus (not as hard as it might seem)
(Or combine reducing the power and switching to OD3 goggles for test mode,
not done in production mode)
In the medical world they:
for visible lasers:
Reduce the power and flip in a 10,000:1 attenuating filter rated for 10x or more of the treatment power, and this is interlocked with redundant safety sensors and safety shutters. A shutter blocks the doctors view or flips in the OD filter before firing.
or
use a aiming laser at a different wavelength
or
or use a physical device to hold the laser delivery probe at a fixed distance from the target for IR/UV lasers.
I think you need to build a aiming ring. This is a black anodized washer mounted on rods held off from the laser source at exactly the focal point, ie you then have a repeatable fixed focus. You then set the aiming ring onto the target materials and hit the trigger, after you follow item one in your safety checklist, which should read: Don't even pick up the laser unless goggles are on. You can see if its working via secondary effects through the goggles, ie smoke, plasma light from the burning material, deformation, carbonization etc.
You use 3 small diameter rods at 120 degrees around the washer, you can see between the rods with the goggles on. You can tape this to your laser, or build a jig to clamp it onto the laser. 5 minutes at the hobby shop and less then 5$ gets you some 1/16" brass rod, and 50 cents at the hardware store gets you a brass washer, you can solder or epoxy the rods to the washer. Get a washer bigger then the pointer body diameter if you can. Sand it to make it rough and less mirror like. Paint it with carbon based flat black paint,(Krylon or engine block paint) or borrow some gun bluing, which usually turns brass deep brown. This reduces scatter if you miss, and increases contrast. Of course you want to take the time to do this right and make it so the aiming ring is not a reflection or scatter hazard in itself.
Look at it this way, a constant distance device gets you a constant spot size. If you add a gas assist device (air or nitrogen jet), you get clean optics and a better cut.
Or buy a 12$ camera from supercircuits.com and hook it to a old TV. Get one with a short range lens.
OK to put crossed polarizers in front of the camera or use a pinhole in front of the lens to reduce excess light into the camera. Or some other attenuator like a ND filter. Webcams are not so hot for this, wrong type of lens, but you can try.
When we work on Co2 lasers, we usually just adjust the lens height for best mode burn and then set the work table programmed for the object height.
Safety pig mode on:
If your in this to burn things, protect your eyes with goggles, keep the burning at arms length. Don't breath the fumes and keep a way of putting out a plastics fire handy, ie water or a extinguisher.
Safety pig mode off.
Steve
