Scale extruder motor current linearly with speed.
49% less heating when running at low speed and standstill, 4% more torque at maximum extrusion rate (15mm^3/s), 15% more torque in high speed movements (un/retractions).
StealthChop mode is used for low speeds (below 900mm/min)
spreadCycle is used above. Transition speed is well above maximum extrusion rate of 15mm^3/s (275mm/min) so mode transition is not expected to be visible on printed surface.
StealthChop is expected to improve printed surface quality (less artifacts).
Warning you can burn extruder motor if it is not the same impedance as original Prusa i3 Extruder stepper motor. There is no current feedback in low speed so lower impedance motor can be burned by over current.
Even there is no direct current feedback, there is no risk for original motor thermal runaway, as motor resistance increases with temperature, current decreases.
Standstill peak phase current is expected to be 500 mA and linearly increase with speed to 970 mA at 900mm/min where spreadCycle constant current regulation takes over and keeps peak current at 805 mA to maximum speed possible.
As motor heating increases with current squared, lowering low speed current from 700mA to 500mA decreases heating 49% in thate mode, where motor spends most of the time.
Enable E-motor cool mode in farm mode only (and experimental menu) - the experimental menu is visible AND the EEPROM_ECOOL variable has a value of the universal answer to all problems of the universe - i.e. two conditions must be met at the start of the FW to enable the E-cool mode. If the user enables the experimental menu, sets the E-cool mode and disables the menu afterwards, on the next start of the FW the E-cool mode will be DISABLED. This is still subject to discussion how much obscure (security through obscurity) we'd like this option to have .
Additional stuff:
* Add serial debug msg to verify if E-cool mode is on
* Avoid access to E-cool mode switch on machines without TMC2130
* Do not allow only M907 E in case of E-cool mode+warn the user on the serial line that the command was skipped
Co-authored-by: D.R.racer <drracer@drracer.eu>
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