[TheForge] waterjet, abrasive waterjet, and wire edm.

[Ries Niemi]

On Mar 7, 2006, at 6:54 PM, terry l. ridder wrote:

> hello;
>
> would anyone have any first hand knowledge and/or experience with
> waterjet and abrasive waterjet cutting?
>
> i have been reading various web sites i found with google and the
> general points they make are that a slower speed make for a higher
> quality cut. i can find no information about reclaiming/recycling the
> garnet abrasive from the slurry. at first glance it would seem
> doable. perhaps the garnet abrasive is so inexpensive that users do not
> bother.
>
> would wire edm be a viable alternative to using plasma or abrasive
> waterjet cutting?
>
> i would rather have a nice square cut at slow speed than a somewhat
> square cut that needs additional work.
>
> -- 
> terry l. ridder ><>

Terry- as I understand it, the abrasive is not recyclable in a waterjet 
machine- I believe it is because it gets mixed with the material being 
cut, making a sludge that is part water, part abrasive, and part 
aluminum, or stainless, or whatever. The abrasive also gets broken down 
to some degree in the cutting action. Since the particles of abrasive 
must be so small to fit thru the nozzle to begin with- .007 to .015 
diameter nozzles- you can imagine how tough it would be to sift only 
the abrasive out of the mix.
So the abrasive is a one shot thing, and an expense.

All metals, as far as I know, are cut with abrasive waterjets. the 
water only cutting is restricted to very soft materials- things like 
rubber and neoprene.

If you look at the base prices of cnc cutting machines, it gives you a 
good idea of why cutting costs are what they are for each process.
Thin stainless steel sheet, like 16 ga, could be cut with a cnc plasma 
machine- 10 grand, for a homemade, very light duty machine.
30 to 60 grand for an industrial quality, commercial machine.
Or by waterjet- probably about 125 grand to 200 grand for a commercial 
machine that will do 5x10 sheets.
Or by laser- in the vicinity of 150 grand to 500 grand for a machine to 
do this, depending on options, such as automatic loaders or unloaders, 
or the addition of a turret punch with 50 stations for fixed punching.
EDM machines probably run from 80 grand or so to 500 grand, but they 
are designed for small parts - if you could find an EDM machine that 
would take a 5x10 sheet, it would be hundreds of thousands of dollars. 
An average 200k or 300k edm machine might have a work area of 20" x 40"

Now obviously, when you are talking about a couple hundred grand for a 
machine, plus more for software, training, maintainence, 
environmentally controlled rooms- EDM machines in particular are very 
picky about temp and humidity- you get into some serious hourly 
charges.

So when cutting, you pick the technology that meets the accuracy needs 
of your project, with minimum cost. At home, you can hand cut with a 
plasma cutter, using templates made from wood or plastic, for $2500 to 
$5000, including compressor.
As soon as you get into cnc machines, the numbers jump very fast, and 
unless your project is grossing well over 100 grand a year, its better 
to job it out to a specialist.
In thin material, up to 1/8" or so, edge quality and square is 
acceptable from all processes. Thicker material may require waterjet 
machines with programmable head angles, to minimise draft angles. Some 
metals can be only be cut by one process or another- stainless above a 
certain thickness cannot be cut by laser, for example, the thickness 
varying from machine to machine.

If you give more info about material size, alloy, thickness, and 
required tolerances, I could give more info about appropriate 
machinery.
For instance, I know a guy in California who runs EDM machines, who can 
give you accuracy down to at least hundred thousandths of an inch. Or a 
plasma shop in Seattle capable of cutting 20 foot by 40 foot pieces.


> Ries Niemi
Industrial Artist

http://www.RiesNiemi.com