@DaBit thank you for an interesting reflection on what I assume has been your journey into low cost CNC and the motion control limitations and issues. There is an ongoing shift away from 'industrial' closed loop AC servo drives for light duty machines because of cost. We see Leadshine respond to that with various hybrids of stepper and servo. These are quite good ideas - combine the low cost of laminated pole stepper motors and the ability to avoid a backlash-inducing gearhead or reduction gearing, with refined drives and 4000 tic/rev position feedback. Add step/direction interfacing which still dominates the low end of CNC and automation. And provide local fault monitoring for overtemperature/rotor blocking/undervoltage. This avoids servo tuning, the cost of high bandwidth encoder counting/decoding at the motion controller (Duet card), resonance-free motion, class-leading cost/axis and (it is claimed by Leadshine) sometimes also faster settling times in point to point motion.
@dc42 If Duet 3 is headed into CNC motion control, the codebase will evolve over time, but D I/O optoisolation (via optional CNC-specific tool boards) and CNC compatible signal interfaces and - in time - axis position registers with 6 MHz input channel bandwidth will have to appear. If the ambition is to go beyond hobby-level machines.
What I'd like to see in the near term is a refined step/dir interface for CNC drives and +/- 10Vdc optoisolated D I/O, including example integrations of a few popular drives from Gecko, Leadshine and the like. Implementing this as a compact CAN connected 2-axis toolboard would be a good cost-containment strategy, not least because of the beneficial effect on wiring and connectorisation costs which are frequently substantial.