Solved Z axis only moves up won't move down past a curtain point

Please help! I have a Robo 3D R1+. The extruder will not move down past a curtain point it will only move up. Please help!

 

I have a Robo 3D R1+ and have had that problem in the past. I'm not certain this is the perfect answer, but it worked for me.

With the power off, move the extruder to the center of the x-rails. Turn the z-screws as evenly as possible until the nozzle approaches the bed. Turn one of them and observe the z-limit switch on that side. You'll also hear the click as it registers contact. Move the other z-screw until you experience the same switch movement and click. Re-check the first side again. Repeat this until both switches are at the same position. I'm not sure if I completed this process with both switches engaged (nozzle on the bed) or disengaged (nozzle up) but it's easy enough to test both ways. Once this is accomplished, the system should be able locate the bed and perform normally.

 

Thank you! I realized the plastic piece that keeps the two parts together had popped off so i popped it back into place. Its now working perfectly!