Answered Z Axis Crash - Spinning Sensor

Yesterday I received my brand new Robo3d R1! Carefully unpacked the packaging, verified z-axis stops were correctly aligned. Started MatterControl. X axis homed correctly. Y axis homed correctly. Z axis crashed into the bed plate and z axis threaded rods continued to spin. The sensor on the right side started spinning around the threaded rod winding its wire around the rod. I quickly turned off the machine ( as this obviously wasn’t right.)


I lifted the print assembly, spun the right side switch back around to un-tangle the wiring. I then noted that the left side switch had not spun around, but was now lower than the right side switch. I unplugged the left side switch and spun it around until it was at the same level as the right and plugged everything back in.


Proceeded to restart the machine. This time the home process worked. I proceeded to print two test prints without issue. Powered down machine and called it a night.


Started up machine this morning and z axis homing now occurs mid air before the nozzle contacts the bed. Upon inspection it seemed the left side z axis switch was disengaging with very little upward pressure on the print assembly. I once again unplugged the left side switch and rotated one revolution. Now it seems that both switches engage at the same time. Z axis homing once again works.


Everything seems ok but I want to be sure that nothing I did here was wrong. The initial crash did cause quite the grinding noise. If I manually rotate one of the z axis threaded rods the other side does not spin. Rotating a z axis threaded rod is easy to do but creates a “grinding feeling” it almost seems like it is trying to rotate the other threaded rod, but that it can’t. Is this normal? Is there a set up procedure for aligning the switch carriages in the event that one is spun around?

 

That is called "Throwing your nuts". When it happens get a sheet of paper. Move the x axis to one side of the bed. Spin the rod until the nozzle just gives a tiny bit of resistance on the paper. Then move the x axis to the opposite side and do the same. Except this time you hold the opposite rod so it doesn't spin move moving the other rod. Keep going back and forth until you get the same height on both sides. Problem solved.

 

Thank you for the reply. Does this mean that it is in fact normal for the z axis threaded rods to rotate individually?

 

Yeah. It doesn't always spin both at the same time when you spin them manually

 

If one rod spins but not both it means that your rod is loose in the helical coupler. Grab the coupler and try spinning the rod, if it rotates you need to tighten down the set screw.

 

If they are going to keep using them they need epoxy the rod to the coupler

 

Is the coupler the metal piece at the base of the threaded rod? This appears to be tight on both sides. But if I rotate one side the other does not rotate.

 

Grab the coupler with one hand and the try to spin the rod. If it spins at all it's loose and needs tightened. If you can't tighten it anymore then you will need to remove the rod and add some teflon tape.

 

Thanks for all the help guys. Helical couplers are good and tight. Did the sheet of paper test. Several prints have gone perfectly.

I did however find that my Z-Axis steps per mm was off. I reflashed the firmware per recommendations in this thread: http://community.robo3d.com/index.php?threads/z-axis-height-is-off.4729/

Printed the test cube and its exactly 2 cm x 2 cm x 1 cm (Z axis). Good to go! Thanks again for the help!