Re: [CAD_CAM_EDM_DRO] Re: water jet

Basically, Liquids are considereed incompressable. There is some
change in volume with temperature change, but to get a significant
change in volume, you have to have a change of state. If my memory
serves me correctly, when water changes to vapor, it expands about
a thousand times. When water changes to a solid, it expands enough
to float. It seems that under extreme pressure, it will shrink a very
small amount. Not enough that a two stage pump would be required.

bob mcknight





Im not sure what you mean by "clipping" the message. Explain and I
will do it. I havent seen any flowrates for the jet calculated which
would give a rough idea of the cut duration. I'm thinking it would be
less than a minute. A one minute cut cycle would be hardly enough
time
to do anything. Imagine trying to cut a large radius and having
program interupts . The programming would be unorthodox to say the
least. Another thing that would have to be taken into consideration is
the volume of the cylinder. When the water is compressed within and
reaches a pressure suitable to perform a task I would think the volume
would be considerable less. A portion of the stroke and internal
volume would be lost compressing the water. Seems the need for a
multistage series of cylinders would be required to over come this.
Starting with a large cylinder then tranferring to a smaller diameter
cylinder progressively until the desired pressure is attained. Now I'm
talking about a pump.

Hey, why doesnt someone just do that? Design and build a multi-stage
pump. Use a block of stainless and incorporate shelf items common
with
pressure sprayers, ceramic pistons etc. Have the intake fed with a
pressure sprayer pump, getting a 1500 psi gain right from the start.
Could be 4 single acting cylinders machined from one block and leave
it massive, with one way checks in between. Crankshaft and
connecting rods could be replaced by linear bearing supported
plungers
attached to ceramic pistons and a camshaft to actuate 0-180-0-180. A
stroke of 1" or less would be sufficient. The last cylinder could
probably be as small is 1/2" in diameter. Still need a bunch of
horsepower.


This would be alot smoother operating than trying to attain all the
pressure in one stroke. This might be the principle already in use for
waterjets. This might even reduce the required horsepower.

Ron






raig <docsys@...> wrote:

A better alternative to your design would be: Two water cylinders in
parallel that work in opposite of one another to supply a constant
flow to the jet and switched/valved at the nozzle.

This then becomes way too complicated, it needs to be simple to
reduce
the cost. Think real simple terms here, like a super-soaker water play
toy gun. You have a set pressure for s set time limit.

>
>
>Developing and storing dangerous levels of pressure/energy in a

large

>vessel was largely the death of the steam engine on a widescale.
>Expensive, Inefficient and unsafe.
>
>

Doesn't the internal combustion engine develop dangerous levels of
energy?

Bruce

PS:
Could you clip your message next time?



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aol://5863:126/rec.crafts.metalworking or go thru Google.com to reach
it if you have trouble. http://www.metalworking.com/news_servers.html

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a sister site to the CCED group, as many of the same members are
there, for OT subjects, that are not allowed on the CCED list.

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