Re: Waterjet

I've been out of town for a while and may not be up to speed on all the
communications related to the waterjet question - But here are some comments
based on my experience with the machines

We have a FLOW brand waterjet in our shop - Installed last November -

Cost - Approx $100,000
Velocity of Water stream - Approximately 2000 ft/sec (Mach 3)
Diameter of Water stream - We are using a 0.040 dia mixing nozzle
Pressure - Adjustable from approx 10,000 to 50,000 psi - (we use 40,000)
Nozzle materials - Water orfice - 0.013 sapphire - cost approx $25
- Mixing nozzle - carbide - cost approx $275 (easy
to break)
Abrasive - 80 grit garnet - usage approx 1 lb per minute - cost approx $0.30/lb
Pump pistons are polished ceramic rods approx 1/2" diameter - (3 pistons)
Pump motor - 35 hp

Many of the above specifications are adjustable but this is what we have
settled on for now as a standard til we obtain more experience with the
machine -

Our machine is equipped to cut both with and without abrasive - Different
nozzle configurations are used for these two operations -

We use it to cut out prototypes of stampings as well as backups, pressure
pads, and stripper plates for stamping dies - We have currently cut up to 2"
thick steel (die shoe cutouts) but the FLOW folks say it will handle up to
4" thick -

The machine is quite satisfactory but the software has obviously been
written by a "computer geek" and not a "machine shop nut" - No offense
intended to either group -

Since I'm also a model builder and woodworker, I've been experimenting with
cutting balsa, plywood, etc - The biggest problem appears to be in holding
the work, particularly with materials like balsa etc - I'm working on some
special tooling and methods to hold the workpiece for such light parts -

Because metal to metal seals are used almost exclusively and special
lubricants are required there is a serious potential problem with fittings
galling - Also, slight leaks at such high pressures can quickly erode the
metal-to-metal sealing surfaces which must then either be lapped together or
replaced -

More serious leaks can be dangerous, particularly brought home once you have
seen these things cutting meat using water only -

A big advantage is the lack of a heat affected zone along the edges of the
kerf - This is helpful when subsequent machining is required - I also
suspect that if methods to hold the wooden parts are developed the lack of a
charred edge would also be beneficial for model kits - I"m working on it

Anybody passing through the Galesburg, Illinois area is welcome to drop in
and visit for the 50 cent tour - Better E-Mail first

Roland Friestad
Cardinal Engineering, Inc.