I'm having a weird issue with bed leveling (Z-Axis) ?? Ender 3 V2

[superiorknightz 0]

 

everytime I try to level it when I go to the the bottom left corner and so on and come back to that corner the z axis drops about .1 mm each go around, it used to drop more than that, this is the lowest I've got it to drop by and cant stop it...

 

still nothing, I squared everything off with a t square and tightened everything precisely,

 

I watched these and did one by one

 

https://www.youtube.com/watch?v=ABpGXcy-cuI&t=931s

https://www.youtube.com/watch?v=rDm9OziZ6dY

did what this site recommended which was part of the first video

https://3dsolved.com/ender-3-x-axis-sagging-how-to-solve/

mind you I've check numerous sites and videos and these above explained everything properly and were the most up to date.

 

I ordered another z axis making it a dual and seeing if that will fix the problem

[GregValiant 1,251]

If the problem was the right side then I would call it "sagging".  Since the problem is on the left side, I'm thinking the problem may be inconsistency in the Z.

Starting at the beginning (and trying to make no assumptions):

• The Z motor has to be aligned with the threaded rod.  The coupler is supposed to take care of that.  If the bottom hole of the coupler (that connects to the Z motor shaft) is not concentric with the top hole (that accepts the threaded rod) then there will be a wobble that can cause the problem.  It is a sort of Z binding.  The fix would be a new coupler.
• The coupler must not drag on the Z motor housing.  You should have a gap between the Z motor housing and the bottom of the coupler of 3 to 6 mm.
• Both set screws in the coupler must be tight so the Z motor drives the threaded rod correctly with no slippage.
• The threaded rod must stay parallel to the Z upright extrusion no matter where the Z is.  With the Z at "0" make an accurate measurement between the top of the rod and the Z upright extrusion.  Then move the Z up to 240 or 250 and measure between the rod and the extrusion again.  The numbers should be the same.  My Ender 3 Pro required a shim of 0.4mm between the Z mounting bracket and the upright extrusion.  I used aluminum flashing, but pieces of paper will work.
• Some lubrication of the Z rod might be necessary.  There are dry lube sprays that won't pick up dust and grit.
• On the extruder motor bracket - the threaded bronze bushing that accepts the Z rod must be tight to the extruder motor bracket.
• I don't believe I've ever seen a problem with the stepper motors on Creality printers.  Lots of other issues, but no complaints about the motors themselves.  If the Z motor has an issue returning to a position, whether from an internal problem or a mainboard driver problem, then it will be inconsistent.
• There cannot be any wobble in the bed.  The wheels (actually all wheels on the printer) need to be properly adjusted to the slots they run in.

In closing (and because the coffee is done) The Z motor is direct drive to the gantry.  On the left side, there should be no slippage or any inconsistency in the stop point.  It is the driver side.  The right side is different as it's a follower.  The videos cover the fact that the X beam must be rigid while allowing gravity to always hold the entire assembly "down" on the threaded rod.  There cannot be any backlash.  If the threaded rod is having to "pull" the gantry down then there are going to be inconsistencies in the stop point when leveling.  They might show up during a print if you enable Z-Hops.  They probably would not show up if the Z motion during a print was constantly upwards.

I HATE throwing money at a problem when I don't understand the problem.  The dual Z drive may fix the problem, or you may just be adding another level of complexity.

 

Remember the words of that noted philosopher Dr. Bunsen Honeydew who said (just as he started his second bottle of tequila) "Gravity is a myth...the earth sucks."

Edited February 11, 2022 by GregValiant

[superiorknightz 0]

@GregValiant very, very true and yes I agree I hate throwing money and hoping it fixes the problem and mind you I'm new to 3d printers. I'm excited to learn and understand all the mechanics of it.

 

I'll try this out and I also found another post about the problem I'm having but in a different format

post

 

 https://www.reddit.com/r/3Dprinting/comments/bi4dnf/what_is_happening_to_my_bottom_several_layers/?utm_source=share&utm_medium=ios_app&utm_name=iossmf 

 

and the first comment by Nenotriple  clarified and sums up what is happening in the most simplest of terms:

 

"To boil down exactly what's happening: The Z screw is turning and moving the left side of the X gantry up, (side with extruder) but the right side is either bound or loose. The Z axis keeps going up, but the nozzle height only changes when the slack is gone. That's why everything is perfect after those layers, except the cube you printed is short."

[GregValiant 1,251]

That is the explanation for "sagging".  The right side isn't keeping up for whatever reason.  The main reason is usually loose screws that hold the left end of the X extrusion to the X motor bracket.  They are a pain because they are only accessible with the gantry off the machine.  That is the sort of thing that your dual Z should fix.

The problem being on the left...I don't know.  If you've checked the usual suspects that I mentioned above, then I'm kinda out of suggestions here, but I'll think on it a bit.

 

[GregValiant 1,251]

I put together this little gcode file.  It bounces the Z up and down four times in the left front corner from 0.1 to 0.0, 0.2 to 0.0 etc and then repeats.  Then it moves up 10.0 to 0.0 four times and repeats.

Get a piece of paper ready.  Auto-Home and level the bed paying attention to the left front corner.  Keep the paper ready and print the file.  After the Z drops to 0.0 there is a 3 second pause before doing the next move.

 

My thought is that you may see what is going on.

 

You did not mention Auto-Homing when returning to the left front corner.  The end stop switches on Creality printers are notoriously inconsistent.  I ended up changing the G28 in my start Gcode to G28 X Y so it wouldn't re-home the Z after I leveled (piece of parchment paper) because the Z=0 location kept changing.

Z Lag Test.gcode

Edited February 11, 2022 by GregValiant

[superiorknightz 0]

I did the lag test and yes it did sag each time.

 

How I leveled it before this test right after I reassembled the printer and did one rotation of bed leveling and auto home and did it again and auto home and so on, but if I kept on doing rotations and didn't auto home after one rotation it would sag. BUTTT what boggles my mind is this THIISSS how is it perfect no stringing no dips and its 20mm all around I measured it with calipers. I'm... I don't know??? I still haven't installed the other z axis I just arrived home said screw it and printed the calibration cube and it came out perfect.... Do you see anything wrong, anything I'm not seeing?

[GregValiant 1,251]

I'd say that looks pretty good.

What was the print speed?

Did you have Z-hops enabled?  I was thinking that any problems might show up in a print with Z-Hops.  That's what that test kind of emulates.

 

Edited February 12, 2022 by GregValiant

[superiorknightz 0]

Print speed was 100mms, z hop wasn't enabled, should I run a test with z hops or is this one of many conditions of having a 3d printer?

[GregValiant 1,251]

That's very good for 100mm/sec.  On a model that small it probably didn't hit unless your accel was dialed up as well.  It probably hit 75 to 80 though.

I use Z-Hops when there are features like large horizontal holes that come to a feather edge at the top before the gap gets bridged.  Those feather edges always curl up, and without Z-hopping over them the nozzle can catch on the print when it crosses the gap, and that can cause the print to break free of the bed.

[superiorknightz 0]

edit: the extra z axis did help but it was all the eccentric nuts, make sure you can move them with little force, not you trying to open a bottle of soda but a little lighter than that

 

SOLVED just added another z axis, printed a spacer for the bottom of the z motors at 1.4mm and leveled both sides with corner levels(post pipe levels) from lowes. Added a washer to the nuts towards the back side inside of the new z axis lead screw bracket and done. I made sure both lead screws were at the right distance from both z axis bars and no more sag.

 

this is the z axis i ordered :

https://www.amazon.com/gp/product/B08RJDW5W6/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

 

I printed a tower to check sag or any other faults and it came out clean😁

Thank you Greg for all the support and the gcode is clutch for troubleshooting🙏

Edited February 15, 2022 by superiorknightz