Pauses during mesh bed leveling  

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adammhaile
(@adammhaile)
Eminent Member

I have firmware 3.7.2 on my MK3S and I've noticed recently that when it does the 7x7 mesh bed leveling at the beginning it will sometimes slow down on a few of the points before continuing. It used to just rapid fire through all of them. But now some will do 2-3 taps rapid fire then pause and do the next couple slower.
Prints fine, but just seems weird. Anything to worry about?

Posted : 08/09/2019 10:09 pm
bobstro
(@bobstro)
Illustrious Member

I find this happens if my nozzle is dirty, or there's traces of something stuck on the bed. If I hear something funny during the mesh bed leveling process, it's a clue to stop the print and check the hotend and nozzle visually.

My notes and disclaimers on 3D printing and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan...
Posted : 08/09/2019 10:21 pm
adammhaile
(@adammhaile)
Eminent Member

@bobstro - What would the nozzle have to do with it? The sensor in use is the PINDA probe isn't it?
And I clean both the nozzle and bed between every print. Only thing I can think that I changed recently was I swapped the nozzle for an E3D NozzleX but I can't say for sure if the issue started before or after that.

Posted : 08/09/2019 10:41 pm
Tim
(@tim-m30)
Illustrious Member

Nozzle change is suspicious on its own.  A longer nozzle means the Nozzle to PINDA height has changed, and the PINDA may not be getting low enough and the nozzle is bumping the sheet.

It is always wise to get more than one opinion......
Posted : 08/09/2019 10:58 pm
adammhaile
(@adammhaile)
Eminent Member
Posted by: Tim

Nozzle change is suspicious on its own.  A longer nozzle means the Nozzle to PINDA height has changed, and the PINDA may not be getting low enough and the nozzle is bumping the sheet.

Nozzle is exactly the same length as previous... standard E3D nozzle size. I double checked when I installed and I've confirmed nothing is hitting the bed already. I just redid the PINDA probe adjustment and still doing it.

Posted : 08/09/2019 11:00 pm
bobstro
(@bobstro)
Illustrious Member
Posted by: adammhaile

@bobstro - What would the nozzle have to do with it? The sensor in use is the PINDA probe isn't it?

The crap on the nozzle will prevent the PINDA from lowering optimally to where it can detect the bed. The firmware seems to have some intelligence to try to detect this.

This is why I do a 160C nozzle warmup before doing mesh bed leveling. The filament is usually soft enough to not cause this problem.

And I clean both the nozzle and bed between every print. Only thing I can think that I changed recently was I swapped the nozzle for an E3D NozzleX but I can't say for sure if the issue started before or after that.

Well, if you've inspected the nozzle, it's not a likely culprit then. Didn't have that info before. But I can assure you, having crud built up on the nozzle will cause this behavior.

I didn't have any issues using Nozzle-X (0.60 & 0.80mm) nozzles, but there can be variations I suppose. Have you observed the mesh leveling process and verified that the nozzle isn't hitting the PEI surface? If the nozzle is not in far enough and your PINDA is at the high end of the range, this might be an issue. What sort of Live-Z values were you getting before? 

Obvious test would be to re-mount the old nozzle (or at least a different one) and repeat. If the problem goes away, check into what's different. Not having the nozzle fully tightened comes to mind as a possibility, but you'd have it hitting the print surface then.

This post was modified 1 year ago 2 times by bobstro
My notes and disclaimers on 3D printing and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan...
Posted : 08/09/2019 11:05 pm
adammhaile
(@adammhaile)
Eminent Member

Yep, nozzle isn't hitting the PEI. On the live-z calibration it worked right at 0.98mm just fine after readjusting the PINDA probe. Was 0.93 before.... but when I adjusted I erred on the side of the probe being slightly lower.

Posted : 08/09/2019 11:07 pm
bobstro
(@bobstro)
Illustrious Member
Posted by: adammhaile

Yep, nozzle isn't hitting the PEI. On the live-z calibration it worked right at 0.98mm just fine after readjusting the PINDA probe. Was 0.93 before.... but when I adjusted I erred on the side of the probe being slightly lower.

OK something completely different, but I did get that happening once when my spring steel sheet wasn't fully flat. Can't recall if it had snagged on one of the threaded screws at the back or there was something underneath. Worth a peek.

My notes and disclaimers on 3D printing and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan...
Posted : 08/09/2019 11:11 pm
adammhaile
(@adammhaile)
Eminent Member

@bobstro - well, I'm stumped then. Removed the plate. Fully cleaned the heater PCB and then even installed a completely brand new, still in package, PEI steel sheet that I was saving as a backup. Does the same thing.

Again, it prints just fine... actually the first layer is even better after my PINDA adjustment. Just find it really weird.

Posted : 08/09/2019 11:32 pm
bobstro
(@bobstro)
Illustrious Member
Posted by: adammhaile

[...] Again, it prints just fine... actually the first layer is even better after my PINDA adjustment. Just find it really weird.

I'm afraid I haven't dug into the source or spent time really investigating what triggers those pauses. Again, my experience has been that it's caused by physical obstructions. It sounds like you're printing OK, so nothing obvious like parts snagging makes sense. I would be curious to see if changing the nozzle back changes the behavior. I've used a dozen or so E3D nozzles and never had any issues arising from the nozzles themselves, so it's puzzling.

My notes and disclaimers on 3D printing and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan...
Posted : 08/09/2019 11:39 pm
Tim
(@tim-m30)
Illustrious Member

Come to think of it, recently was reading something about the mesh level code and how there was a recovery mechanism for certain errors discovered ... delta between taps too far apart??   Oh well - call it a mystery.

 

It is always wise to get more than one opinion......
Posted : 09/09/2019 1:11 am
adammhaile
(@adammhaile)
Eminent Member
Posted by: Tim

Come to think of it, recently was reading something about the mesh level code and how there was a recovery mechanism for certain errors discovered ... delta between taps too far apart??   Oh well - call it a mystery.

 

Well, that's the mystery I'm trying to solve. Was hoping someone from support who might know that answer would see this 😉
At least to either tell me everything is alright or that I need to dig further.

Posted : 09/09/2019 2:05 am
bobstro
(@bobstro)
Illustrious Member

You could always try opening a GitHub issue and see what, if any, response you get. Be sure to describe all the steps you've taken including cleaning the nozzle and heated bed.

My notes and disclaimers on 3D printing and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan...
Posted : 09/09/2019 3:07 am
david.a66
(@david-a66)
Honorable Member

i think it retries if the first measurement on a point differs too much from the stored value

Posted : 09/09/2019 4:07 am
Robert-mm200
(@robert-rmm200)
Noble Member

If I got bored with the pauses - I would run calibration again. That way your stored values will match current.

Posted : 09/09/2019 4:18 am
chris.n6
(@chris-n6)
Reputable Member
Posted by: david.a66

i think it retries if the first measurement on a point differs too much from the stored value

Yeah, that or if there is too much difference between the readings. too much bounce so it slows down. 

Posted : 09/09/2019 5:50 am
bobstro
(@bobstro)
Illustrious Member
Posted by: chris.n6

Yeah, that or if there is too much difference between the readings. too much bounce so it slows down. 

Oh sheesh, yes. That's it. When 7x7 was first released, it would fail under those conditions and you had to start over. This varied quite a bit depending on the stability of your print platform. They added the pause between retries to de-bounce the procedure. I completely forgot about that. So to answer @adammhaile ... It's OK and it's a FEATURE. Ideally, your print platform is rock solid and this doesn't happen. You could try it with your printer on the floor to see if that clears it up. If so, consider making your platform more solid.

This post was modified 1 year ago by bobstro
My notes and disclaimers on 3D printing and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan...
Posted : 09/09/2019 6:01 am
adammhaile
(@adammhaile)
Eminent Member

@bobstro - Ah, interesting. Wonder why it's bouncing? It's on a shelf but it's pretty solid. Though I've been tempted to put like an 18x18" paver stone under the thing to really make sure.
Thanks!

Posted : 09/09/2019 11:03 am
bobstro
(@bobstro)
Illustrious Member
Posted by: adammhaile

@bobstro - Ah, interesting. Wonder why it's bouncing?

Possibly just hitting a resonant frequency now and then. Do you hear much during leveling?

[...]I've been tempted to put like an 18x18" paver stone under the thing to really make sure.

Thanks!

I went down the paver path. I'm pleased with the results, and I get no pauses during leveling. 

My notes and disclaimers on 3D printing and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan...
Posted : 09/09/2019 2:45 pm
chris.n6
(@chris-n6)
Reputable Member
Posted by: adammhaile

Wonder why it's bouncing?

It could be a loose screw, belt, or bearing, or it could be one side of the shelf is looser/farther away from the support. And since you are talking leveling it could be so small an amount that you'd never notice, but the printer does. 

Posted : 09/09/2019 2:52 pm
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