Re: [CAD_CAM_EDM_DRO] Re: Direction follower ? Water jet

> CO2 is in the
> deep infared so glass is very opaque.

I realised glass was opaque to IR but not to that extent. How does it work,
just by letting it heat and cool quickly?

[Back to original posts]
You should check which bands the glass absorbs best and then choose your
laser band using that.

Nd:YAG pulsed (1.06um short wave) is harder to make, particularly if you
want a converged, 'continuous' beam, but you can steer it using fibres round
funny angles. The rods are roughly $400 - 1000 a piece and you need to
handle them as if they are made of talcum powder. One hair line fracture
from stressing during expansion or over pumping and it's dead; bin material.
But with these ones you can get the mirrors plated onto the end of the rod
so you don't need to adjust them. The laser is arranged with a crystal rod
in the middle and pump flash lights either side which are fired using
massive caps in a silered chamber. High fire rates are tricky to keep up due
to major cooling needs and also killing the lamps or saturating the rod.

CO2 is continuous discharge, all you need is a neon sign transformer or
three for the pump source. The laser is a piece of boro-silicate glass
inside another larger piece that acts as the water cooling jacket. At either
end are metal plates and these form the electrodes. Mounted in them are a
partial reflector at the hot end and a total reflector at the other. The
total reflector can be polish silicon, usually with a silver coat, gold,
copper, etc. Gold is one of the best. The partial one is almost always zinc
selenide on home brew ones. These are anywhere between $40 - 80 per lens.
The inner tube is filled with CO2 and pumped down to a vacuum. Robinaire
sell a beautiful pump for this at about $180 that'll go right down to 20
microns (Ample). Although Welch pumps go on ebay for nothing and these will
pull evil vacuums. I've even seen diffusion, ion and turbo-molecular pumps
on there. These lasers need tweaking into alignment and their 10.6um beam
isn't steerable with fibres. But the arrangement to shoot the beam down the
gantry and onto the work requires max, 5 more mirrors.

It's not strictly CNC related but I thought the info might give you a hand
deciding which is which. If you want anything specific let me know.

John H.

> By brother-in-law owns a glass shop/factory in Manila.
>
> He says laser is the way to go for cutting glass. Cuts clear through
> at production speeds, low maintenance, high start-up costs. Slowly he
> is replacing the Ultrasonic units which are low maintenance, lower
> start-up costs but, can be slow and very messy.
>
> High power co2 lasers are not that difficult to build. The higher
> efficiency units use expensive germanium mirrors and lots of them to
> fold the laser into a managable space. Used units can be had for a
> dime on the dollar. Check out some of the Laser Lists. CO2 is in the
> deep infared so glass is very opaque. Heat dissapation with laser
> cutters is not a big problem. The CNC table needs to handle only the
> weight of the laser lens and final mirror, so it can be relativly
> light duty.
>
> One thing I learned when hand cutting glass with a wheel, always lube
> before each score and break as soon as possible. I'm guessing Glass
> must have a certain amount of self healing. An old score never breaks
> as nice. Try it.
>
> The lighter fluid trick and hot wire trick is great on large dia.
> tubing.
>
> Tom M.
>
>
>
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