Some people may have seen where a few of us hijacked a drag knife thread to talk about hardware off topic. Sorry OP.
I was able to remix a drag knife to increase the offset by a couple of mm’s, which effectively enabled me to cut lots of circles in 7mm double wall cardboard pretty reliably. Useless for anything with corners because the huge offset trashes the minimum radius of cut.
The answer for thicker material seems to be a tangential cutter. I thought I would share my progress working on this. Two problems; hardware and software. As Ryan said, the hardware is the easy part, but I’ve had a go at it, and built on my Fusion 360 skills a bit. I had some linear bearings and 10mm rod to hand and came up with this:
The main idea is that the knife is set to a zero offset position, and retains the spring loaded capability. I had to borrow Ryan’s pineapple! It seems to function well enough, so that leaves the software.
Generating the gcode might take a bit more work, but I have found this, which may help:
The trouble is, so far it just eats all my memory and dies. I will get into a bit of debugging with that next I think.
Assuming either with that method, or another method of producing gcode with tangential a axis moves (and corner moves), the next problem for me will be electronics and any firmware changes needed. I assume some tinkering with Marlin will be needed.