Geeetech

The extruder nozzle is about 5 mm above the bed, but won't go any higher when I press the Z up manual control, it makes a loud buzzing noise for a second.

Hi Jon30b,
You don't say if this is a new build where the Z axis is stuck, or if this has happened after 100 successful prints...
It sounds like something is fouling the movement.
If you switch off the printer, can you manually turn the two axis screws and make the nozzle rise above the bed ? - Any resistance felt ?
What screws are being used - M8 x 1.25 thread or T8 leadscrews ?
Where does the buzzing come from - the motors ? - Left, right, or both ?
Does the axis seem to stick on one side (Go angled before stopping, then stick) or both sides together ?
A bit more info is required to home in on the problem.
Gerry

Sorry for not giving more information. It's a new build, I haven't successfully printing anything yet. I can turn the axis screws to make the extruder go up without any resistance, then I can make it go to its home position which is 5 mm above the bed. The axis screws are M8s. The buzzing is only coming from the left motor, and the vertical position stays the same, there horizontal rods to not go angled. Even if I change the home position to 50 mm higher, after pressing the home button I get the same short buzz and it stays in the same position. I can't see anything that is getting in the way.

Hi, You can see if your z-axis can move correctly.
Check if your threaded rod is bent;
Check that your coupling is installed correctly;
Check if your brass nut is too tightly installed and adjust it properly;
Check if your lever is carded (lubricated for lubrication).
I hope this can help you.

Hi Jon,
OK , you can move the Z axis up and down manually, and you say there's very little resistance...
Let's say for the moment that the rods maybe fine.
I suggest a test as follows...
Take the threaded rods out and then set the Z axis moving up...
The motors should spin away freely.
Do the motors spin without buzzing ?
Do they both spin together in the same direction / speed ?
If they don't, we've found an issue...
If they do, we'll have another test to perform.
Let us know how you get on...
Gerry

It all seems ok

The motors spin without buzzing in the same direction at the same speed.

I took out the threaded rods out of the couplings and put them in again and now it's moving freely.

Hi Jon,
Great !
I guess they were previously slightly off on being square...
Happy printing.
(It's time to try calibrating now !)
Gerry