Z axis won’t move on Geeetech Prusa I3 X

oysteinATpcsoft · Post by **oysteinATpcsoft** » Tue Sep 08, 2015 3:02 am

When using Repetier-host to move the Z axis, I only get a noise but not any movement on the Z axis. The noise is like the motor is trying to turn but are not strong enough. (X and Y axis works fine)
When I try to turn the threading rods with my hand they are quite hard to turn. I don't know if the rods are bent, the linear bearings are bad or if I have done something wrong.

What I have tried to fix this:
I have eyeballed all the roods, and they look pretty straigh.
I have lubricated the rods with oil.
I have check that the threading rods are not stuck in the holes at the top.

I don't know what more I can do.
Can you help me to figure out what is wrong?

Mark · Post by **Mark** » Tue Sep 08, 2015 8:56 pm

How about reassemble the rods? And make sure the linear bearings can move smoothly then tighten the screws.

dolphi · Post by **dolphi** » Tue Sep 29, 2015 3:34 pm

Hi,
I had a similar problem and battled it for days (with Prusa I3 X).
It seems a very common problem (The Z motor is more complex than the others, it has two motors. The left and right sides of the Z axis have to be at exactly the same height. It has to carry a heavy load against gravity)
See also:
http://www.geeetech.com/forum/viewtopic ... 22&t=16218
http://www.geeetech.com/forum/viewtopic ... 17&t=16890
http://www.geeetech.com/forum/viewtopic ... 17&t=16765

Here is how it was solved in my case:
In my case the two Z motors were making a grinding noise, when trying to change the Z-axis location through the Repetier host program. The Z axis did not move. This was the behavior immediately after the assembly has been completed.

Remember to power off the motors when you turn the threaded rods by hand (turning the Z couplers at the bottom of Z axis is easier than turning the threaded rods themselves). When the motors are on, they resist moving the threaded rods by hand. (The motors are also affecting each other when they rotate).
Remove the top acrylic plates for Z axis and make sure the smooth rods are moving easily when you lift them and then lowering them back to their location.
Make sure with a caliber that both sides of Z axis are at the same height. This can be done by measuring the distance between the two acrylic plates as demonstrated in the photo below. If they are not level, there will be more resistance to their movement. Rotate the coupler in one side by hand to lift or lower that side.

: measure z axis.jpg (124.67 KiB) Viewed 62417 times

Change the Z-coupler location, probably lift it a bit (I have seen in photos that they were a bit above the acrylic plate that lies beneath them). When the couplers are lifted, the bottom side of the coupler is connected firmly to the motor shaft, and the top of the coupler is holding the threaded rod.
Make sure the voltages between the screw and GND of the step motors drivers is in the range 0.9-1 V (mine was about 0.8v). It increases the power to the motors, so they can overcome higher resistance. (Search the forum for explanation how to do that).
Is it not moving only when Z axis is at 0 location? Try rotating the Z couplers by hand to a different Z location, and then test whether the motors can move at that location from the Repetier Host program.
Changing the couplers location, had fixed the initial problem of stuck Z axis immediately after assembly. There were still other problems with Z axis movement.
In my case after the initial fix, the Z axis could only move up to location 40 mm, and at that location, again the Z axis motors made a grinding noise and stopped rotating.
Looking carefully at one threaded rod I have noticed that at that location, there is an imperfection at the thread of the threaded rod. This imperfection caused a slightly higher resistance when that imperfection was inside the Z axis nut.

: z threaded rod imperfection; z threaded rod imperfection.jpg (78.81 KiB) Viewed 62417 times

This was solved by applying lubricant (WD 40) to the rods at the imperfection location and above and below it, and then rotating the couplers by hand back and forth several times in order to move the imperfection several times through the Z axis nut. After moving the imperfection through the Z axis nut by hand, I started to move the imperfection through the Z axis nut from the software. After about 20 such movements, the Z axis begun to reliably move through the imperfect point.
There were several such imperfect points at different heights of Z axis. Using the same method of lubricating and going through these weak spots back and forth several times solved the inability to move through these locations, and eventually the Z axis was reliably moving up and down the full 15 cm!

cheesemarathon · Post by **cheesemarathon** » Tue Oct 06, 2015 6:36 am

hi i have the exact same problem as well its taken up alot of time trying to fix it. any more ideas on how to fix this?

Mark · Post by **Mark** » Tue Oct 06, 2015 5:47 pm

Re: Z axis won’t move on Geeetech Prusa I3 X

帖子由 dolphi » 周二 9月 29, 2015 3:34 pm
Hi,
I had a similar problem and battled it for days (with Prusa I3 X).
It seems a very common problem (The Z motor is more complex than the others, it has two motors. The left and right sides of the Z axis have to be at exactly the same height. It has to carry a heavy load against gravity)
See also:
viewtopic.php?f=22&t=16218
viewtopic.php?f=17&t=16890
viewtopic.php?f=17&t=16765

Here is how it was solved in my case:
In my case the two Z motors were making a grinding noise, when trying to change the Z-axis location through the Repetier host program. The Z axis did not move. This was the behavior immediately after the assembly has been completed.

It's a great solution, thanks for sharing!

Humu · Post by **Humu** » Fri Jan 08, 2016 5:43 am

My stepper motor also did not work, the problem was the electric charge. I have welded electric wire and now the printer is functioning properly.Sorry translation of the text is Finnish English Google.
Toivottavasti tästä on jollekin apua. Ongelma oli pieni mutta selvittely vei aikaa todella.

HellyeaSkoda · Post by **HellyeaSkoda** » Thu Sep 15, 2016 3:39 am

Humu wrote:My stepper motor also did not work, the problem was the electric charge. I have welded electric wire and now the printer is functioning properly.Sorry translation of the text is Finnish English Google.
Toivottavasti tästä on jollekin apua. Ongelma oli pieni mutta selvittely vei aikaa todella.

was it an earth problem, i noticed with one of my screwdrivers when i touch the pot of the z axis some of the motors buzz

Xaroos · Post by **Xaroos** » Sun Jul 16, 2017 3:13 pm

I had the same problem along with lots of other problems!
i acualy noticed that the 2 shaft that holds the extruder and X motor were quit tight where it goes to the X motor side, i used the files and losened them a little bit ( becarful not to file too much just take the paint away softly) and used a bit of lubricant on the 2 screw shafts that takes the extruder up and down and its working fine now,

YouraT · Post by **YouraT** » Fri Aug 11, 2017 3:23 pm

I also had severe assembly problems with one side of the Z Axis - on the side with the X-Axis motor, the carriage went up and down easily, on the other side, very very stiff. After tearing my hair out for a while, I tried turning the linear bearing through 180 degrees (i.e. used the mounting screw hole that was at the front to be at the back, and vice-versa), and magically everything freed up !

Not entirely sure why that helped, but possibly worth a try if things aren't working for you.

bda2206 · Post by **bda2206** » Sun Sep 30, 2018 11:05 am

I found the smooth rods are not 100% straight, by having the x axis assembly at mid point and twirling the rod just above the bottom hole. It went in, in one position and was 1-2 mm out at 180 degrees. that almost fixed it..
finally, I fixed mine by loosen the screws holding the linear bearing just a little, then a little dab of glue to stop the screws going any further out.