Yes, the spindle load (and through that the spindle rpm) is certainly a measure or an approximation of the material removal rate (or cutter contact angle).

Your idea would be to use standard ('stupid') geometry-based toolpaths and then have a 'smart' cnc-control that adapts the feedbrate depending on spindle load. I think that would work and it's certainly doable/testable using EMC.

The adaptive-clearing CAM approach is the other way around. You have the 'smartness' in the generation of the toolpaths, and use a 'dumb' controller. If your toolpaths are generated for constant material removal rate then you can run them on a 'dumb' controller that doesn't measure spindle load and compensate for it.

Anders

I'll think about your spiral idea - but can't promise anything...

For machining more complex shapes than circular pockets the cutter movement algorithm need to be much smarter.

I wonder if you generate some sort of 'guide curves' or similar based on the pocket geometry which the cutter moving algorithm then tries to work with? In other words, you don't simply cut 'blindly' wherever you can find the right engagement angle, but there is some overall plan to the cutter movement.

As you can see, due to the curvature of the stock when it's towards the centre, and the way that the side of the stock becomes much flatter relative to the size of the cutter when the radius is large, the pitch of the spiral should be different.

The naive implementation of a spiral cut is to write (f*t*sin(t), f*t*cos(t)) for t > 0, which gives a constant pitch of 2*pi*f. But when you do it properly, you get a pitch that's smaller when t is small, and you should have a function like f(t) which starts at 0 and asymptotes to the original value of f.

I haven't calculated the equation for this (too lazy and I don't have MatLab). Maybe you could, and publish it.