It's definitely possible to use a CNC machine to mill the shape of a rocket engine. You can do some pretty crazy internal milling with a 5-axis machine:
The fuel actually flows through the pipes and voids in the red-hot engine, where it absorbs the heat that would otherwise melt the engine. It then flows back up to be burned.
You'd need an endoscope, not a robot arm, to mill that out!
And neither an endoscope (obviously) nor a robot arm would likely be rigid enough to mill in these materials. Robot arms are typically only used when milling wood, plastic, or soft modeling materials. A CNC mill in metals like the exotic Nobium alloys used in these engines needs incredible rigidity which robot arms just don't have. Consider the hardened tool-steel shafts of the end mills used in the first video - and those are easily broken, while just cutting aluminum!
I think you mean EDM, electrical discharge machining. Typical wire EDM usually needs a hole all the way through the material to start, but sinker EDM would work. Interesting idea, wonder if anyone's tried it.
yeah, i was thinking more of an endoscopic robot arm, it would probably need quite a few entry points, and the those holes would need filling again, you could tap those and put a screw it afterwards.
but maybe it's the coming towards end of subtractive manufacture.
https://youtu.be/RnIvhlKT7SY?t=14s
But the problem isn't the shape of the bell at all. It's that the wall of the bell is not solid, but hollow, filled with plumbing.
http://heroicrelics.org/info/f-1/f-1-thrust-chamber.html
The fuel actually flows through the pipes and voids in the red-hot engine, where it absorbs the heat that would otherwise melt the engine. It then flows back up to be burned.
You'd need an endoscope, not a robot arm, to mill that out!
And neither an endoscope (obviously) nor a robot arm would likely be rigid enough to mill in these materials. Robot arms are typically only used when milling wood, plastic, or soft modeling materials. A CNC mill in metals like the exotic Nobium alloys used in these engines needs incredible rigidity which robot arms just don't have. Consider the hardened tool-steel shafts of the end mills used in the first video - and those are easily broken, while just cutting aluminum!