Hello.
I am new to 3d printers and have purchased a He3D Prusa xi3 kit.
After assembling and reviewing many related blogs and homepages, I managed to make the step motors and heaters work.
And the steppers work in correct directions,after jumper and trimmer settings.
However, there is a big problem.
Although I have wired the Z axis limit switch correctly and uploaded the firmware
from Arduino as supplied, that switch works in the reverse way.
It should stop the Z axis motors when the Z axis is moving down and the switch is pushed.
However, when I move the Z axis up and down with Cura's heatbed leveling function, the motors
don't stop when the limit switch is pushed while Z axis moves down and the head keeps moving
down,finally scratching the heatbed aluminum tray.
The Z axis motors stop when the Z axis limit switch is pushed while the Z axis moves UP, however.
I have checked RAPS 1.4 wiring images on the Web and ,according to them, I have correctly
wired and connected the Z axis limit switch and the steppers are connected in the correct polarity
as they rotate in the correct direction.
I have also checked configuration.h of the included firmware files but haven't seen anything particular;
the settings seem to be correct.
So what might be the cause that causes the problem?
Thank you.

no idea what their documentation says, but this sounds like you have the z endstop plugged into the max endstop plug and not the min endstop plug

ie your z endstop is like this



If this is the case you need to move the z endstop cable one pin to the Left to move it on to the z min endstop position

I don't have this hardware/software but in an effort to help:-
You say "I move the Z axis up and down with Cura's heatbed leveling function". I don't use Cura but if this is an auto bed levelling function it may be expecting different wiring and an inductive sensor.
"stop when the Z axis limit switch is pushed while the Z axis moves UP" . It should do this on the way down. The software then knows its at the end, as Dust points out you do need the switch wired the same as the software is set to, which can be max (away from the bed) or min.
Can you confirm that when moving down activating the switch stops the movement? If so you can use the traditional method to level the bed.