Re: [CAD_CAM_EDM_DRO] Re: LOOKING for homeshop EDM or its power supply?

Hi Jerry:
You are theoretically correct, of course.
Nevertheless, wire EDM performance is always quoted in square inches per
unit time.
The reason it's quoted this way is that salesmen make assumptions that the
wire thickness is small and constant for all machines, and thus consider
only the material thickness and the rate of progress through the block.
They pretend that the cut has effectively no thickness.
Yes, it's not strictly correct, and yes it's totally misleading,
particularly when you compare actual machining speeds with those quoted.
In wire EDM there is a "sweet spot, where the material thickness is thin
enough to allow excellent flushing and minimal wire bowing, yet thick enough
that the maximum power that the wire will tolerate can still be used as
efficiently as possible.
For many machines, it's around 2" thick, and the peak volume per unit time
will be removed under these conditions.
A 6" block will not only have a far slower rate of advance, the amount of
metal removed will be less per unit time because the flushing conditions are
no longer ideal.
A 1/4" block will have a faster linear rate of progress, but will also
remove less material per unit time, because the full capacity of the wire is
not being utilised.
The capacity of a wire EDM is far les than 34 cu in per hour...that would
mean that you could totally disintigrate a plate almost 6" x 6" x 1" thick
in an hour, and there's no way it's even close to that.
The actual capacity is more like 0.408 cu in per hour, but that doesn't
sound nearly as dramatic as 34 sq in per hour!!
Nobody multiplies by the slot width (typically 0.012" or so).
They also don't tell you what block thickness they actually used!!
Those cheatin' lyin' bastards!!!
So there it is, for what it's worth...probably pretty much off topic by now.
Cheers

Marcus

----- Original Message -----
From: "Jerry Kimberlin" <kimberln@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Wednesday, July 16, 2003 8:03 PM
Subject: Re: [CAD_CAM_EDM_DRO] Re: LOOKING for homeshop EDM or its power
supply?


> turbulatordude wrote:
>
> >This is one reason wire edm is so popular. the slit is small so less
> >mass is removed.
> >
> No, the same amount of mass is removed. The width has nothing to do
> with it. You have to measure it in cubic inches per unit time.
> Anything else doesn't make any sense as an EDM is a three dimensional
> machine and EDM is three dimensional metal removal. All slots have a
> width, length, and depth.
>
> >The back cover of this months EDMtoday shows a wire EDM rated for 34
> >in2/hr. that is 34 square inches per hour of a 34 inches in a one
> >inch thick piece of stock.
> >
> Should be 34 in3/hr. Lots of dummies out there. Education isn't what
> it used to be especially in math.
>
> JerryK
>
>
>
>
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