Ошибка парковки оси z

I don’t think that’s a bug but intended behavior. The Mini doesn’t have mechanical end stops, it senses the torque change when idling on the z axis. See https://forum.prusa3d.com/forum/prusaslicer/mini-z-axis-issue-when-parking/. The sound can be disconcerting but shouldn’t be a concern.

End stop may not the right word, and agree its not a mechanical end stop, However the way the mini detects the limit is not being applied to the Z axis. hence the bug.

The upper limit for Z is just software based.

If you turn the printer on or after a reset, the printer doesn’t know the Z axis height. After all you could’ve moved it by turning the lead screw by hand. It only knows Z origin after it did its homing routine which uses the sensor to detect the bed.

After this procedure it knows how far up it can travel.

If I wanted to avoid this issue, I’d probably set the Z position to an «unknown» value and avoid any upward movements unless it has homed all axes. You can’t just home automatically after a reset either, because you don’t know if there’s still something on the bed.

The upper limit for Z is just software based.

If you turn the printer on or after a reset, the printer doesn’t know the Z axis height. After all you could’ve moved it by turning the lead screw by hand. It only knows Z origin after it did its homing routine which uses the sensor to detect the bed.

After this procedure it knows how far up it can travel.

If I wanted to avoid this issue, I’d probably set the Z position to an «unknown» value and avoid any upward movements unless it has homed all axes. You can’t just home automatically after a reset either, because you don’t know if there’s still something on the bed.

Can the Prusa team confirm if this z limit is derived from software, or from firmware? It looks like the x axis is derived from firmware, so the z axis should be also.

The upper limit for Z is just software based.
If you turn the printer on or after a reset, the printer doesn’t know the Z axis height. After all you could’ve moved it by turning the lead screw by hand. It only knows Z origin after it did its homing routine which uses the sensor to detect the bed.
After this procedure it knows how far up it can travel.
If I wanted to avoid this issue, I’d probably set the Z position to an «unknown» value and avoid any upward movements unless it has homed all axes. You can’t just home automatically after a reset either, because you don’t know if there’s still something on the bed.

Can the Prusa team confirm if this z limit is derived from software, or from firmware? It looks like the x axis is derived from firmware, so the z axis should be also.

Firmware is software… :-). End-Switches would be hardware.

There are no switches on the Mini. It detects the bed (Z=0) using the SuperPINDA sensor and X/Y start and end points sensing motor current. If a motor gets stopped while being powered, the current will rise. There is no detection method for the high Z value. Otherwise the axis would have to go up all the way and back down for every homing cycle.

Please Update the Firmware, the Z motor is capable of detecting z end stop by reading pin 11 of U6.

Thanks for reaching out to us.

This is the expected behavior and not concerning in any way.

The X and Y motors can sense homing via collision detection at the end of the axis.
This feature is not used for the Z-axis homing because the PINDA probe has this duty.
The collision sensing is only used on the Z-axis during the XYZ self-test.

Ultimately, detecting a collision in the Z direction is unnecessary and there is nothing to be worried about the current behavior.

Can this issue be closed?

Michele Moramarco
Prusa Research

Even if it’s not damaging the printer (afaik steppers are fine when loosing steps) it’s not necessarily «nice» in my opinion if the axis just runs into the limit for a few seconds. Also it makes a horrible sound.