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