Mesh bed leveling - extruder goes up on 2 points - normal?  

RE: Mesh bed leveling - extruder goes up on 2 points - normal?

Hi @all,

same behavior on my side. (On other points of cause)

I have already reloaded different  FW's (3.8.1 , 3.7, 3.9 rc1) but the behavior still exists.

Any help or hint would be greatly appreciated.

RE: Mesh bed leveling - extruder goes up on 2 points - normal?

@sil

Make sure there is no debris on the back side of the build plate nor on the heat plate.  I found a tiny bit of filment on the build plate when this started happening with me.

Jerry

RE: Mesh bed leveling - extruder goes up on 2 points - normal?

Hi Jerry,

thanks for your reply.

I double checked the plates and cleaned them with alcohol and tighten up all srews. But these strange z-axis movements are still exists.

The print quality is still perfect, so i will see what the future brings....

RE: Mesh bed leveling - extruder goes up on 2 points - normal?

@sil

Hello,

this behavior started also happening with me after i pgraded the printer to MK3s...i dont recall seeing it on the mk3.... i also tried the 3.81  firmware which was running on my mk3... i nuilt the mk3s upgrade a couple of days ago and this started happening...i suspeted the 3.9 firmware and went back to 3.81 bbut its still hapening...

did you find a solution ?...i know its afeature... but why should it satrt doing this all of a sudden...

regards

RE: Mesh bed leveling - extruder goes up on 2 points - normal?

I had this when the print bed was uneven and it vanished when i trimmed the print bed (using the nylock mod). You can read the mesh bed leveling measurements using the "G81" command (and start the mesh bed leveling by the "G80" command). Or using the bed leveling plugin in Octoprint.

RE: Mesh bed leveling - extruder goes up on 2 points - normal?

Hello Christian,

sorry no solution yet. Actually this strange "lift up" is on every point, while the hotend moves from the left to the right position.

The behaviour is absolutely normal while the hotend moves from the right to the left position.

However, the printed result is still excellent.

No further ideas from my point but i will check the bed leveling plugin in Octoprint as mentioned by olaf-groeger.

RE: Mesh bed leveling - extruder goes up on 2 points - normal?

My guess is that the mesh bed leveling algorithm has certain expectations about the height when measuring a point. When the sensor doesn't trigger within the expected range it measures a second time. When the result is still not good but in an acceptable range it accepts that point and continues to the next point. When the measurement is not in the acceptable range the mesh bed leveling cancels and the z calibration is started.

Like i said this is only my guess (seeing from what happened when i calibrated the nylock mod).

As you noticed the bed doesn't need to be in optimal conditions to get good print results. But when it for instance adds to a bad first layer calibration it might result in lousy adhesion on certain parts of the bed.

RE: Mesh bed leveling - extruder goes up on 2 points - normal?

My MK3S Textured Sheet started doing the hop on spot 9 after 2 months and maybe correlated with its first bath.  I have noticed a random occurrence at different spots when I fail to set the plate squarely on the heated platter.  

Have no idea how the PINDA works except it senses either a self-induced magnetic field or maybe a field present in an iron object.  I think the PINDA output is binary but not sure.  It has to be capable of a great deal of precision as it sets the baseline for printing accurate to at least 50 microns (50/1,000,000 meters)

RE: Mesh bed leveling - extruder goes up on 2 points - normal?

Either live with the double tap, or lower your PINDA.

RE: Mesh bed leveling - extruder goes up on 2 points - normal?

@peter-k42

I've tried that with no joy. Tried it at .5, .8, 1.0 and 1.2. Same hop at site 9/49.

I still have no idea how the PINDA or FINDA works and a Google search provided no additional info.

RE: Mesh bed leveling - extruder goes up on 2 points - normal?

If I am correct, the Pinda is just a magnetic sensor.  When it gets closer to a ferrous item, the inductance increases.

RE: Mesh bed leveling - extruder goes up on 2 points - normal?

Das macht mein mk3s schon immer ist normal 

Einstellungen/MeshBett Ausgleich/Z-probe Nr. 1x/3x/5x

RE: Mesh bed leveling - extruder goes up on 2 points - normal?

That makes my mk3s always normal

Settings / Mesh bed compensation / Z probe No. 1x / 3x / 5x

RE: Mesh bed leveling - extruder goes up on 2 points - normal?

Posted by: @peter-k42

Either live with the double tap, or lower your PINDA.

I recently changed from a 3x3 to a 7x7, following a recommendation here.

When on the 3x3, it would never 'double tap', but when switching to 7x7, one point near the rear will sometimes, not always, double-tap.  This is on a steel sheet where the coating on the opposite side was partly ruined (torn) by aggressively removing a stuck print.  I always assumed this was probably due to some surface irregularity due to the damage.

RE: Mesh bed leveling - extruder goes up on 2 points - normal?

I would need to go back through the firmware, but I vaguely remember something about the double tap happening when the sensed plate position was to far out of variance from the stored positions obtained during initial calibration. Don't take my word on it. Unfortunately, I'm too busy to go reading the firmware right now.

You could repeat the initial setup calibration (which stores the baseline z-positions) and see if the double tapping diminishes.

RE: Mesh bed leveling - extruder goes up on 2 points - normal?

I had the same issue, can confirm @Guy-k2.

My issue was that when I fixed the hotbed, the distancer washer tube slid out of the way and I bent the bed. Once I fixed that, it was fine again.

I would check your hotbed assembly in detail and see if there is something wrong.

Do you have another steel sheet to test with?

RE: Mesh bed leveling - extruder goes up on 2 points - normal?

Hi all,

finally i found out what the problem with my MK3S was.

I mounted a lamp on the right upper shaftholder and whenever the printer did a z-calibration the left side of the X-axis touched a screw.

The upper deadpoint of the left side of the x-axis was bit lower then  on the right side. That caused my problem.  I redesigned the lampholder and now evierything is fine.

Hope this information helps someone....

Regards

Sil

RE: Mesh bed leveling - extruder goes up on 2 points - normal?

@1agkirk2

hello,

i  am also getting it on Spot 9/49

RE: Mesh bed leveling - extruder goes up on 2 points - normal?

Does it still occur when settings -> mesh bed lvl -> comp. for magnets -> is set to OFF?