Prusa i3 Pro B - Z axis problems, struggling to move

[mike_mcl]

Hi, I have a newly purchased and assembled i3 Pro B, and am encountering issues with the Z axis

X and Y axes work fine, they home correctly and motors have no difficulty

Z axis however struggles to reach home. Movement is problem free in the top half of the axis, but the closer to the bottom, the more the motors seem to struggle

Below 50% = high pitched whine
Below 75% = grinding noise and failure to move

I have (poor quality, sorry) video of this, click to watch with sound -
https://goo.gl/photos/uGhUXaWKcqCccjdg9
https://goo.gl/photos/zEirc3jjpahViuvVA

In the 30 seconds before I started filming, I had given a 'home' command to Z axis, starting near the highest point

X-axis ends are as level as I can get them (I have a level+caliper on the way, but am currently using the top part of the frame as a parallel edge to eyeball, and testing by seeing how easily the extruder moves along the X-axis)

Possible reasons I suspect -

- (most likely) smooth Z axis rods are VERY difficult in places to push through linear bearings - recommend lubricant?
- the smooth Z axis rods are not *quite* 100% straight (about 0.5mm in warp becomes visible by placing the two rods to be touch while disassembled, then rotating them while keeping ends touching)
- the frame may not be 100% square - getting wider or narrower at the bottom?

Are there likely issues to do with assembly I should be looking at, or is this a manufacturing tolerance issue?

many thanks in advance!

[bang]

You can take a look at this file to make some troubleshooting:

I3 Z axis.zip

(281.49 KiB) Downloaded 2803 times

[LindaMarika]

You are most likely angling the Z-axises towards the middle when you're tightening the x-axis belt. I'd recommend putting the locking rings on the insides (thus securing the ends where they are) and THEN installing and tightening the x-axis belt.

[Pouly]

I have just purchased the same model and was about to post a similar experience.
My right z axis was having a lot more resistance than the left one, resulting in jamming the right one.

I found a semi-solution, i have done 2 things :
1. changed the top piece that holds the 2 bars so that it only holds the smooth one and keep the screw one free
2. unscrewed the bronze ring that connects the screw to the x axis.
3. Apply WD40 but that was really 1 and 2 making the difference

This is what was causing the resistance for me.

Now is still doesnt print well, but i got other troubles to fix

[palma]

Z axis issue

Recently purchased Geeetech Aluminium i3 Pursa pro
Great instructions and manual. It took only 6 hours to build and start the first test print. Everything went well other than needing to lubricate the lead screw and loosen the Z nut mounting screws. Made three successful prints of varying heights before it stopped printing anything over 5mm above the bed.
Problem = When trying to move the z axis up, it only goes 4-5mm before the left z motor starts vibrating while the right motor continues for a few more millimetres before the carriage jams.
Read all the forums and tried several things…

Inspected threads with a magnifying glass…No irregularities.
Disassembled the z lead screws….everything moves smoothly including the rods.
Swapped out the z axis plugs…no change.
Installed spring loaded z nut mounting screws …no change.
Loosened the x axis wing nut….no change.
Swapped out the left stepper motor with one I know is working….this worked initially, I was able to move the z axis all the way up and down, but after cycling the power supply and homing the printer, I was back to having the same problem. (This may be the key?)
Considering upgrading to anti backlash nuts and upper ball bearing supports for z screw.
Any ideas?

[nagymester]

Hi!

This is the problem with me. The Z axis is in the lower sector. There are some Prusa i3 Pro W's. Did you solve the problem?
Thank you very much for your help!

[1138]

[quote=nagymester post_id=82607 time=1518590785 user_id=64058]
Hi!

This is the problem with me. The Z axis is in the lower sector. There are some Prusa i3 Pro W's. Did you solve the problem?
Thank you very much for your help!
[/quote]

- Oil the rods/screws properly.
- Make sure that both carriages are aligned.
- Check the gain of motor drivers and optionally increment it.

[nagymester]

We managed to solve the problem. I swung a rigid connection between the engine and the shaft and adjusted the threaded shaft of the Z-axis. So it works great, there is no need.