Because the error is in the height, and that's the Z axis, there is no belt to tighten. I have checked the screws that attach the rod to the step motor. I did run a PID and made the suggest adjustments. There was a little improvement on the height error, but still off by 1.2mm on 40 mm height print.
Where the Z axis gantry attaches to the frame:
They should ride along the frame with wheels. Make sure the wheels aren't too tight.
A lot of manufacturers will use helical nuts there, which aren't one way tightens, one way loosens, it's more of you play around with it until you hit the sweet spot. Depending on the exact setup, usually you want there to be a little bit of play - you can use your finger to start rocking the wheel back and forth a little, but not enough to move it up or down the frame.
Too tight and the Z axis motor isn't going to have enough power to overcome the resistance put up by the wheels so it can't go up as much as it should each time.
Edited by Slashee_the_Cow
1
As Slashee surmises, it's most likely an issue with the Z mechanicals, but there is a slim chance you may need to calibrate the Z steps/mm. It is something that only rarely needs to be done though.
If you grab the right end of the X beam with two fingers and move it up and down there will be some movement, but it shouldn't be loose.
Thank you both for your help, and I wanted to let you know that your ideas worked... On Paper. Before adjusting, 20mm print was 19.4mm. Loose where the gantry would slowly drop down - 19.4mm. Tight where it had zero play but yet moved easy - 18.9mm. I lubed the Z-Screw before any test prints. So... The mystery goes on. But, again, thank you.
Maybe Z axis out of level? I have seen such problems sometimes when someone try to level a z axis to the bed axis not knowing that this is the wrong method doing this. I can't really believe that a manufacturer choose wrong steps settings for a t8 rod. This is a very basic calculation and will never change. The pitch of an lead screw is per definition exact. A difference of 1.1 mm on such a small distance of 20 or 40 mm makes no sense except there is a mechanical problem that cause a z-axis to be out of level. I would suggest to check whether your z axis is out of level. Do it in the old way manually.
First delete the saved mesh values for auto bed leveling, if your printer have auto bed leveling. Home your z axis and move it up say 100 mm then try to exactly measure the height on both sides of the z axis against the bottom profiles. They have to be exactly the same. Move the axis again 50 or 100 mm. Now your measurement difference have to hit exactly that value on both sides. If not, find the problem as there is not a lot left over that can cause such a problem and most of them was already told.
After this is achieved level the bed manually so that it is in level with the z axis.
Two things that just came in mind while writing this post:
Do you change the bed temperature during printing or are you leveling your bed cold or while it is heating up? This can cause as well height problems and is easily to check.
Maybe your print bed is warping too much in some locations. This can be check by comparing the mesh bed leveling values for a cold and a heated bed.
@DivingDuck: On my E3V2 Neo I did get the problem once that the Z axis gantry did get stuck at a bit of an angle. Had to unscrew the top part of the frame from the printer, pull the gantry off entirely, and put it back on carefully. Possibility exists that's just Creality trying to sell you on the dual screw upgrade.
@Slashee_the_Cow, this was what I had in mind. Or wrong reassembling of a dual screw after a cleaning session. Many possibilities for generating such problems. Anyway, hope, he will find a solution for his problem.
Leveling the X beam on my Ender is a pain. The two screws that hold the X beam to the left side trolley plates aren't accessible when the beam is installed.
Here is my fix...a 6mm (1/4") hole in the Z upright.
When the Z is at about 100mm I can get an allen wrench through that hole from the rear and access the inboard attachment screw.
With the outboard screw tight, and the inboard screw just snug, I take the Z up near the top cross member (which I know is square to the Z uprights) and I measure down from there to the X beam on the left and on the right. If the measurements are different I nudge the right end up or down as required. When the measurement is the same on the left as on the right, the sucker is square to the frame.
I then lower the Z so I can get the allen wrench into the hole and final-tighten the inboard attachment screw.
Since my build plate is on springs and is adjustable up/down, I will occasionally take the build surface off the machine and level just the metal plate. Constant tweaking of the leveling screws can introduce a bow into the plate and re-leveling just the plate takes care of that.
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Slashee_the_Cow 267
Is the H32 properly tuned? Make sure everything's straight, belts have appropriate tension, wheels are correct tightness, stuff like that. I had a problem on my Ender-3 v2 Neo once which was basically the same thing, turned out one of the wheels on the Z axis gantry was too tight so that the printer wouldn't go up as much as it wanted to each time.
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