<p>Having recently got a new bed plate (PEI covered steel) I decided to run a bed mesh calibration with a higher than usual number of points (23,23) to see if there were any high spots or dips.</p>
<p>Klipper measures the bed by moving left to right along the x-axis nearest the front, probing at each point, then onto the next line where it moves right to left then left to right on the third line and so on.</p>
<p>The result showed ridges indicating the height was measured differently when moving in one direction or the other. Since I didn't believe the plate actually had ridges, I tried a couple of other sizes (19,19) and (15,15). In each case, I get a slightly higher measurement when the probe is moving right to left than left to right</p>
<p>My setup is an Ender 3 with a 3D Touch (BLTouch clone) mounted on a Hero Me 7.2 hotend fan assembly.</p>
<p>What would likely cause this effect? I'm not aware of anything being out of adjustment and the difference is probably about 0.1mm, but I feel it should be happening.</p>
<p><a href="https://i.sstatic.net/qgFFS.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/qgFFS.png" alt="23x23" /></a>
<a href="https://i.sstatic.net/7i88V.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/7i88V.png" alt="19x19" /></a>
<a href="https://i.sstatic.net/y745t.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/y745t.png" alt="15x15" /></a></p>

CC BY-SA 4.0
2023-06-28T21:28:38.333Z
My first guess would be that your V wheels are slack on the gantry, causing the carriage to tilt slightly depending on which direction it was last pulled in. The further off-center your probe is, the more this will be amplified.
R.. GitHub STOP HELPING ICE
CC BY-SA 4.0
2023-06-29T00:01:39.493Z
"Slack" is obviously a relative term. There didn't appear to be any play, but this possibility occurred to me shortly after posting so I've just tightened the eccentric nut slightly. I also wondered if there's a small play in the belt, so have also checked that's as tight as it can be. The extra movement of the end wheel was barely noticeable! However, I just ran a test and the effect is still there. The difference, at worst, is 0.15mm,
StarNamer
CC BY-SA 4.0
2023-06-29T00:34:40.500Z
Definitely hardware. I modified klipper/klippy/extras/bed_mesh.py to always probe going left to right and the effect goes away.
StarNamer
<calibration><build-plate><klipper>
Bed mesh registers different height when measured in different direction
StarNamer
# Bed mesh registers different height when measured in different direction

(Asked by: username_0 on 2023-06-28)

Having recently got a new bed plate (PEI covered steel) I decided to run a bed mesh calibration with a higher than usual number of points (23,23) to see if there were any high spots or dips.

Klipper measures the bed by moving left to right along the x-axis nearest the front, probing at each point, then onto the next line where it moves right to left then left to right on the third line and so on.

The result showed ridges indicating the height was measured differently when moving in one direction or the other. Since I didn't believe the plate actually had ridges, I tried a couple of other sizes (19,19) and (15,15). In each case, I get a slightly higher measurement when the probe is moving right to left than left to right

My setup is an Ender 3 with a 3D Touch (BLTouch clone) mounted on a Hero Me 7.2 hotend fan assembly.

What would likely cause this effect? I'm not aware of anything being out of adjustment and the difference is probably about 0.1mm, but I feel it should be happening.

[![23x23](https://i.sstatic.net/qgFFS.png)](https://i.sstatic.net/qgFFS.png)
[![19x19](https://i.sstatic.net/7i88V.png)](https://i.sstatic.net/7i88V.png)
[![15x15](https://i.sstatic.net/y745t.png)](https://i.sstatic.net/y745t.png)

**Tags:** calibration, build-plate, klipper

> **Comments:**
> **username_1**: My first guess would be that your V wheels are slack on the gantry, causing the carriage to tilt slightly depending on which direction it was last pulled in. The further off-center your probe is, the more this will be amplified.  
> **username_0**: "Slack" is obviously a relative term. There didn't appear to be any play, but this possibility occurred to me shortly after posting so I've just tightened the eccentric nut slightly. I also wondered if there's a small play in the belt, so have also checked that's as tight as it can be. The extra movement of the end wheel was barely noticeable! However, I just ran a test and the effect is still there. The difference, at worst, is 0.15mm,  
> **username_0**: Definitely hardware. I modified klipper/klippy/extras/bed_mesh.py to always probe going left to right and the effect goes away.  

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## 0 answers

