End stop limit switches
On my old Rep Rap that I built ten years ago there were electro mechanical limit switches on each axis. On the Prusa Mk3 there are no physical limit switches. How do they achieve the end of travel limits without limit switches? Some sort of load sensing perhaps?
Hi Rocket3
Prusa use TMC2130 Stepper drivers and that enables 'stall guard' sensing.
the ends of the X and Y Axis are sensed when the printer bumps the carriage into the end of travel for the X and the Y axis during homing, the stall guard feature indicates that the motor has stopped moving the carriage by monitoring the motor drive current increase when the travel stops.
The Z axis has an inductive sensor (Pinda) to the right of the nozzle on the X carriage.
the Pinda is initially orientated about 2mm higher than the nozzle during assemble, or recalibration. and then during homing, the Pinda senses the presence of the build plate. this results in the nozzle being near to the build plate, but safely higher than the first layer nozzle height, then during first layer calibration the user, alters the Live Z setting, in order to bring the extruder down, nearer to the build plate, in order to achieve the perfect first layer height... Live Z is ALWAYS a negative value whilst the available range is 0.00mm to -2.00mm, useful values are usually between about -0.700mm to -1.8mm. every printer has a different best value for PLA, and a different Best value for most other filaments. also the value changes between smooth build plates, textured sheets and satin sheets.
consequently there is no need for physical endstops
On a side note, Are you a triumph motorcycle fan? (I have a Trophy 900 tripple)
regards Joan
I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK