Z axis won't move anymore

Hey guys,

I just finished the build of the Mendel90 from nophead's kit (it's my entrance into the world of 3D printing). I started testing and all the axes moved fine, however I had some problems with the extruder and a wrongly wired cable, but everything could be solved with a bit of solder...
Now that everything should be working, I wanted to level the bed and configure the Z axis but it somewhat won't move anymore. I tried editing the Z_HOME_POS (since the carriage was at the top i put in 0) but it did not help. When I want to make it move I see the motors start but then they are stuck and you can only hear a high-pitched sound indicating that the motors are "trying" to move or something.

Does anyone know this problem?

Best,
siggg

Update: It seems like I found out the problem: I manually lowered the Position of the X axis and now I can just move the carriage up but not further down.
So, whenever i start the printer and pronterface, it assumes being at 0 position and it only lets me move up. When pressing the Z Home button, it moves up until the end of the rod but is not stopped by the Z-stop, so the motors turn on. Is there anything wrong from hardware or is it only the firmware, that is wrongly configured?

Edited 1 time(s). Last edit at 01/24/2015 12:09PM by siggg.

If you are using the firmware provided it is correctly configured.

Before homing you should only be able to move up. When it hits the switch it should stop and set the position to Z_MAX_POS, which is about 203 and then you should be able to move down.

If it doesn't stop when it hits the switch, check the switch is working by manually pressing it as described in the manual. If the axis is not level it is possible the other side hits end first. In which case just lower it manually a bit. If the switch is not fitted correctly it will miss the x end.

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[www.hydraraptor.blogspot.com]

OK, got that now, thanks for your message, the switch always worked but I messed it up in the firmware by putting strange Z_HOME_POS values then.
However I now tried to find the right value and found something like 206.7 mm should fit. When I entered that value and uploaded it, I wanted to test it and put in "G1 Z-204" (from home position) to see whether the nozzle is quite a bit above the bed. However it was just touching the bed (and said Z:0.00 when putting in "M114"). I then decided to switch back to a value of 203.8 mm. When I tried to set the nozzle just above the bed again by moving the Z axis to Z-203, it stopped well above the bed (about 3 mm) and on asking for the value the machine is reading, it said Z:0.00. What is the mistake there? It should be at least telling me Z:0.80 or am I wrong?

Best,
siggg

The gcode is absolute, not relative, so if you send it to a negative Z value it gets clipped to 0 by the firmware soft limits.

Please follow the calibration procedure in the manual.

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[www.hydraraptor.blogspot.com]