Picture mount (mat) cutting with curved opening

As if I hadn't enough on my plate, I'm considering the possibilities of this as a next project.

A picture mount cutter ( I think you call them mats over your side of the pond) that will only be needed to cut two different sizes, but they are curved, top and bottom, with the sides at 120 degrees to each other, to display folding fan leaves.
I had started with the idea of cutting them manually, as no great numbers nor speed is needed, and the use of pivoting arms would work, as the two curves are arcs of a circle, and have a common centre.

So, in its simplest form, a gantry across the work piece (1/16" mount card) with a pivot at its centre, the card held in register guides with vacuum bed.
Hanging under the pivot, an arm in the form of a pair of round shafts, carrying a sliding carriage, which in turn carries the blade carriage.
This part can be stepped 90 degree at a time around its vertical axis, each time to a fixed position, but the blade itself plunges at 45 degrees to that vertical axis, in a sliding holder.
This allows in the first position, with the carriage fixed and the arm rotating, an arc to be cut with a 45 degree bevel (It's normal to cut from the back of the card, so the plunge cut doesn't show from the front).
Pull out the blade, rotate the head 90 degrees, and plunge in.
With the arm fixed, slide the carriage towards the centre to a stop, and the straight side is cut.
Lift, rotate, and plunge, and with the carriage fixed but the arm free to rotate, the lower curve can be cut.
Lift, rotate, and plunge, with the arm fixed and the carriage free, cut the second straight side, up to the top curve.
All movements would be to adjustable stops.

And that's at its simplest !
OK, I'll try and draw a diagram over the weekend.

The next step gets complicated. Now add stepping motors etc.....

The card would be 18" x 18" maximum, the rotating arm needs to swing up to 150 degree, the sliding carriage needs only 6" free movement, and the plunge of the blade would be limited to about 1/4", or less.

I'd be very happy to read any observations/suggestions for getting this out of my head and onto the workbench.
I have looked at converting my present home built 3 axis cnc, but would prefer a dedicated machine, leaving my original one free.

John

Here is the diagram of the shape I want to cut. Although the size is a variable, the principle of the machine as I see it should be as simple as possible.
CNC mount cutters exist, and run to about $10K. Because I'm looking for simplicity, and limited variability, my budget is more like a few $10's.
I've got plenty of steppers of a variety of sizes, and the approach to the mechanical side should keep the structural cost down, so ingenuity should be uppermost in everyone's mind.
I'm starting by buying in suitable blades, as used in manual cutters, and will work on the blade carrier first, then work outwards from that.

John

Greybeard,

There's a Fletcher 1100 on eBay for $250.00 or best offer, unfortunately it's a manual machine.

Fletcher 1100 Professional Circle and Oval Cutting System | eBay

Jeff...

Thanks for heads up on that one, Jeff.
While it isn't too far from my other part time location in Corinth, it does give me some design ideas.
Regards
John

It's a bit late, I realize. But did you come up with a Cnc router mounted mat cutter??

This is even later ! Now in USA with a manual mat cutter that I built.
Much water under the bridge, but if my profile has been updated correctly, I'm now in Corinth, MS.