Z-Axis Issues

[ATMorris]

I've had my Geeetech Prusa I3 for a couple months now, and solved countless issues with it, but I have reached an impasse. Ever since I constructed my printer, the two Z-Axis threaded rods and joined motors have been quite a hastle. They often get slightly out of sync, and produce a horrible grinding noise. I have prevented this by switching around the driver boards (I'm running the GT2560 board), but after a little while the axis rods would be back out of sync. When I remove the rods and let the motors spin on their own, they are constantly switching direction, and when I put the slightest amount of resistance on one it reverses its direction as well. Is this an endstop issue? Maybe hardware or firmware related? If anyone has dealt with this issue before or knows a solution, I would very much appreciate a quick reply. Thanks!

[Mark]

you can unplug the endstop to verrify it. and if it doesn't work, I think you need to reinstall your firmware, it seems your pre-installed firmware is the test one, it will make the motors rotate back and forth all the time. you can download it here:
http://www.geeetech.com/forum/viewtopic ... 10&t=17046

[ATMorris]

I've done as you recommended, and reinstalled the Marlin firmware. Every other aspect of the printer runs quite smoothly, except the Z-Axis. The switching motor directions is pretty much gone, but the two motor rods are constantly out of sync as they were before. With careful tuning of the axis rods by hand, I can align the two rods so they can run smoothly, but that does last long at all. It seems the slightest disturbance can cause the motors to produce the loud grinding noise. This occurs every time the X-Axis assembly reaches the Z endstop. Also, when the Z-Axis is in this position (close/hitting the endstop) it seems as though one motor is spinning while the other is not moving at all. When the printer head is near the build plate, the motors are easily thrown out of alignment, and I have to reset them by hand. When the printer hear is a bit higher, the motors don't seem to have any issues, and I can move the Z-Axis up and down at my leisure. I have tried some test prints, and starting the prints is impossible due to the motors spinning out of sync, but if I force them into place I can get the printer working fine for a minute or two before they fall back out of sync again. Thoughts?

[Mark]

I think you can check two things:
1) check the Z axis motor driver voltage. usually it is 0.8-1.0V.
2) check the two sides of the Z axis, see if they are on the same height.
you can refer to this link to check them:
http://www.geeetech.com/forum/viewtopic ... 13&t=17038

[BrendaEM]

I (also) think that one of the motors is stalling.

You might have the current set too low for one. It would be interesting to check the current for the one that works, and then set the other one as that one is.
If the current is set too low, the motor will stall; if it's too high the driver will get too hot and shut down.

There is a leveling gauge on Thingverse, that might make setup more convenient.
http://www.thingiverse.com/thing:280974

If you have some kind of grease that's safe for plastic, perhaps you could put a little dab on the top of the screw.

I am in the process of doing a leadscrew with integrated stepper upgrade on mine.

[Warren]

as for calibrating the height of each z axis screw I use my digital calipers. I get the carriage down to my bed level.(really almost any level would do. Then I measure the distance from bottom of the linear bearing to the motor mounting plate. Then I turn off the motors in Repetier and manually adjust the other side to match the same height. Also get some Super Lube synthetic grease. That will help cut down on the binding. Definitely get the grease if you're seeing black on the all-thread rods. I perform the caliper check at least once a week or any time I hear one of the stepper motors bind. Only other minor change I made was replacing the couplings with a set that had been threaded for the all-thread rods. Just using the set screws won't grab the threaded rod worth anything.

[Kaupy62]

Check that the threaded rod is in line with the coupling. I had the same problem so I put the locking rings on the lower x axis rod on the inside of the z housings to prevent the x axis drive belt from pulling the z axis rods in toward each other.

[H****s]

Hi ATMORRIS It sounds like from what you're describing you are having an issue with your motor driver board. Two things I would suggest. One try switching the motor connections (swap the z motor connections on the gt2560 board with each other). If that doesn't work adjust your driver board here is a good video for that. https://youtu.be/bItYRMLGoVc
Good luck hope this helps