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

> It seems that glass seperation could be much more easily done with a
> laser heat/cool/crack mode.

I have seen a guy writing his name on a glass bottle using an Nd:YAG pulsed
laser. It was between 30 and 100 watts but I don't think that'd be enough to
cut a piece of window glass efficiency, especially at speed.

> this would be instead of stock removal that would be done with
> water. also I am not sure of the cost of the laser, but it would
> seem that the operational cost would be much less.

A laser would be much, much less. In fact, you could build it yourself for a
couple of hundred if you have the parts. Maybe a thousand or few for a
really nice higher power one. The thing you must think about now is that
even incredibly stupid things such as the colour of the glass or the amount
of impurity in it will drastically effect the absorption of the beam at
1.06 - 10.6um (IR lasers). That may lead to cracking and lots of fine tuning
for each piece of material, or even each area of the glass. Although normal
window glass does absorb IR it's not very good, so lots of that energy will
be going to waste. IR is even pretty bad for metals since lots of them just
reflect 90% of it back. The work piece would ideally be matt finished, dark
in colour, absorbive in the IR spectrum and the laser Nd:YAG, since the
shorter wave lengths seem to be better absorbed and are more easily guided
down fibre optics (Expensive ones though).

> But you did offer one VERY interesting bit of information, and that
> is what pressure is needed ? obviously foam and cloth cuts at much
> lower pressures than plastic and plastic at lower pressures than
> steel and so on. Just where does glass fit on the list ?

I would have a look for tensile strength tables and things to do with Molar
hardness, I'm sure I remember seeing glass somewhere on one of the standard
tables that 'give you an idea'.

> assuming a centrifugual load on the pump, a reduction of about 20% of
> the pressure would require only about half the motor hp.

This is an intresting point and one I don't understand. :-) Is the pressure
to input HP curve an exponential one?

> I am not sure if it is shear force (pun intended) or part abrasion,
> part supersonic speed of the water that does the cutting.

If you're cutting material like metal or rock it's very heavily abrasive in
mode of operation. Without the sapphire dust the metal cutting ability will
fall off. The fact it's sapphire tells you that. If it wasn't that important
there would be no point running such an expensive media through it (Sapphire
is second to diamond in hardness).

Things like tip pressure, media size, transverse speed and all the rest
effect the cut quality. Something coming to my mind is a more mechanical
form of cutting it. Like, a router loaded with a small diamond burr or end
mill, possibly even a dentist's 400krpm drill (All zeros and K's in correct
places)? Have it mill through the glass or tile with water running onto it
to clean all the gunk off as it goes. Along side it you could rig up a grit
blasting head at 4000psi or so and have the machine run over it's cuts at
the end with the grit gun. Bearing in mind that the back of the glass will
still probably be sharp. Maybe even some sort of arrangement to have a gun
either side? :-) A bit more expensive but still, far cheaper than a water
jet table.

Best wishes,
John H.