Negative X,Y,Z values allowed?

While changing extruder and firmware I crashed my hotend into the bed twice. I later found out the cause was a negative Z value in my gcode, as the stl file was now "on top" of the bed in the first place. My bad.

I am not sure if all the firmwares are equally happy about going to the "negative" side of the axis, but as I am using MIN endstops it is not mechanically possible to go to negative coordinates. But what is worse is that my printed did not honor in that case the endstop (as after homing the endstop was already pressed). This happened to me using the Marlin 1.0 beta.

I wonder if this is the standard behaviour of the firmwares, as I think it should be safer not to allow negative coordinates in the first place.

Any thoughts?

misan

i have seen this too in all but one strange and older firmware i have, i do not know why it is like that, i would like to thing that if the endstops are hit it would just stop there untill it goes the other way.

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[mike-mack.blogspot.com]

I guess you are correct as far as end-stops are not hit before the motion starts, 'cause if they are, no change will be detected while the motion goes one.

misan