Ok, so to heck with the formulas. Something told me it wasn't simple. 

You call that "crude" !
I guess Michelangelo was a "chicken scratcher". 

I like your idea !
Would most likely provide enough force but not sure about the kinetics of it.
Questions ...The velocity at the  knife  looks to be reduced by about 3:1 ? 
.. meaning the e-punch would provide more of a "push" than actual impact ?

Relying more on the impact allows all actuation to cease well before the tooling contacts the material relying solely on the kinetics of the mass to complete the cutting.
and making it as fast as absolutely possible.


I was tinkering with a variation of yours but using an air cyl instead of the e-punch.
The cyl would fully extend as quickly as possible leaving the cutters slightly open.
The kinetics of the mass would make the cut and the lower return spring would immediately open the gap so the matl. could continue.

See pic. Something a bit more cruder.

I like your pivot pin and return too ... just as I had envisioned. Much simpler than a slide.

Thanks Ian, much appreciated,
Russ

Something else just came to mind.
Back in 75 (19 that is, not 18) I worked at a place that made fluorescent lighting fixtures.
A 10 stage roll form formed the U channels, CANS for 4' and 8' lights.
There was a guillotine type "on the fly" cutter at the out-feed that had an air reservoir and a rubber air bladder for actuation. Sort of like the air ride on a semi.
The sliding portion of the die probably weighed 200 lb, or more.
Anyway, the air only propelled the mass and probably contributed little, if any, to the actual cutting.

How about a motor turning a flywheel and an electric clutch to engage/disengage? Or, I had a friend do something very similar a while back using a servo and drive with detect switch going straight to the drive. Its insane fast and does it all day. Get a good braking resistor for sure. I was wondering how it would hold up starting and stopping so quick and so often but been running without issue for a few years now I guess. All day every day or close to it.

 :)Hi Brett.
That is sort of what we are using now. It is massive, somewhat complex and worn badly. It's also an antique. Been running since the 60's.

It uses a large motor through a gear reducer to a large 12" clutch/brake that engages a double gear cutting device.
Massive spur gears that are cleared out in the middle with 2 pinch cutter blocks inserted into the body of the gears.
When triggered, it makes 1 revolution and pinches the material in two.
There is a variable speed adjustment on the straightener to  insure that the surface speeds between the cutter and the straightener match precisely.
Man, I wish I could draw like you folks, but here is an idea of how it works.
The sketch represents the gear with the center grooved out and the cutter block installed. There would be one mirror image above of course.
The little vid shows the relationship of the gears running and the cutter blocks.
Thanks to ART for Gearotic. 

Russ

Also had the notion of a spring loaded design cocked and fired by air cylinders.
Would be instantaneous and plenty of time to get it cocked for the next shot

Hard to decide.

Am I right in thinking that with your current spur gear system, the cutters travel with the wire as they're cutting? If so I reckon that's VERY neat.

The trigger and sear would forever be a problem child.  You could use an air cylinder arrangment to drive teh hammer similar to what you have drawn.

The trigger and sear would forever be a problem child.

Why is that? 

Am I right in thinking that with your current spur gear system, the cutters travel with the wire as they're cutting? If so I reckon that's VERY neat.

Yes, it's a very cool set-up. I wish I had a pic of it here.
I searched for hours on the web and never found an image or example.
It is from Germany and has no name on it. Might be custom built .... like a brick **** house.
The gears are about 4" dia. and the pitch is heavy ... Here's a Gearotic example of how the gears are cut. One drives the other and there's a bunch of backlash which makes it difficult to cut accurately without damaging the cutters. Quite a tremendous amount of pressure when the "pinch" comes around.

There is one micro switch to disengage the clutch and engage the brake with the cutter blocks about 180 deg away from the cutting pos. And there's a small speed controlled dc gear-motor with a trigger cam that trips another switch to undo the brake and engage the clutch making one rev and completing one cut. The length of matl. is governed by the speed of the constantly rotating DC motor cam.
The straightener runs continuously  as well as the drive to the gears. Speeds are matched so when the clutch engages, the cutter does not "pull" or "buckle" the material.

Quote

The trigger and sear would forever be a problem child.

Why is that? 

I see TP .... I think that would work too.

The sear would be quite robust and made of tool steel. Maybe a full .25" of engagement and well lubed.
I have similar in other apps and works flawlessley .... millions of cycles.
I'm curious as Brett.
What issues do you envision ?
Thanks,
Russ