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Still no (manual) bed level correction for Prusa MINI?  

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RFC2549
(@rfc2549)
Active Member
Still no (manual) bed level correction for Prusa MINI?

Ever since I got my MINI I've had this issue: first layer calibration shows that the left side of the bed is about 0.10 mm "higher" than the left. This means that, to get a good first layer on the left part of the bed, I get poor adhesion on the right side (which isn't great, because printing things closer to the vertical arm - i.e., on the right side of the MINI's bed - actually reduces vibration and ringing). But, to get good adhesion on the right, the nozzle scrapes along the bed on the left (which is worse).

Why the sensor reads slightly different heights, I have no idea (there's  some vertical deflection to the arm depending on the X position of the head, but that deflection is there both while printing and while doing the auto levelling, so that shouldn't interfere with the mesh). I'm guessing that either the sensor's reading is slightly affected by the proximity to other printer parts, or the issue is that the sensor is reading the distance to the bed (ignoring the sheet?) and the sheet itself doesn't have uniform thickness (i.e., it's slightly thinner on the right).

Regardless of the reason for the error, this would be trivial to fix if there was an option in the printer's menu to manually adjust (i.e., add a correction factor to) the auto-level mesh. As there is in other Prusa printers (and as I'm pretty sure we were told there would also be for the MINI). So, why hasn't this been implemented yet? Is there some reason why it can't? Is it a "crippleware" conspiracy to make other models more desirable? Assuming it can and will be added to the MINI, is there an ETA?

 

Posted : 21/05/2022 6:38 am
Chris Laudermilk
(@chris-laudermilk)
Estimable Member
RE: Still no (manual) bed level correction for Prusa MINI?

It's probably that your printer isn't quite square. Take a look at these resources:

https://help.prusa3d.com/article/squaring-your-mini_158518

https://forum.prusa3d.com/forum/hardware-firmware-and-software-help/oh-no-were-skewed-prusa-mini-edition/

It takes a little while, but is worth the effort.

Mini+ (kit) - Revo Micro

Posted : 23/05/2022 2:25 pm
RFC2549
(@rfc2549)
Active Member
Topic starter answered:
RE: Still no (manual) bed level correction for Prusa MINI?

I am aware of those pages. Neither of those will fix the problem I'm having.

If I move one side of the bed up by 0.1 mm (or if I tilt the arm to make it 0.1 mm lower on that side), the sensor will read it as 0.1 mm higher, and will still apply the same (incorrect) correction to it.

That's why other Prusa models have a manual correction in addition to auto-bed levelling - to correct errors in the sensor's readings and prevent the sensor from adding an error of its own.

But, for some reason, the MINI still doesn't.

 

Posted : 23/05/2022 4:38 pm
Diem
 Diem
(@diem)
Famed Member

That's why you recalibrate.

Cheerio,

Posted : 23/05/2022 6:47 pm
RFC2549
(@rfc2549)
Active Member
Topic starter answered:
RE:

I'm not sure what you mean by "that's why you recalibrate". What kind of "recalibration" can compensate for errors in auto bed levelling on the MINI?

On other models, you just follow these steps:

https://help.prusa3d.com/article/bed-level-correction_2267

... but the MINI doesn't support that, at least not with the official firmware.

 

This post was modified 1 month ago by RFC2549
Posted : 23/05/2022 8:55 pm
Diem
 Diem
(@diem)
Famed Member

First make certain your print sheet is scrupulously clean and flip it, then if the mesh-bed levelling doesn't deal with it go to:

https://help.prusa3d.com/article/squaring-your-mini_158518

Then recalibrate your first layer Z and try again.

If the frame is square then the bed *is* level.

Cheerio,

Posted : 23/05/2022 10:21 pm
RFC2549
(@rfc2549)
Active Member
Topic starter answered:
RE: Still no (manual) bed level correction for Prusa MINI?

You don't seem to understand. My problem isn't with the bed being level (or not). 

My problem is that, after the automatic bed levelling (which completes just fine), the first layer is always slightly "thicker" (i.e., the print head is higher) on the right side, leading to poorer adhesion. If I use Z-adjust to make it stick properly on the right side (which is the only control available for first layer calibration on the MINI), then the nozzle touches the plate on the left side.

In other words, the auto-level data (for whatever reason) is skewed, and the printer is following that (automatically generated) data.

Other Prusa printers (ex., MK3) have a mechanism to deal with that, so it's clearly a known problem, that was "solved" a long time ago by giving users the "bed level correction" option, as you can see here:

https://help.prusa3d.com/article/bed-level-correction_2267

The same reasons that led to that being implemented in the MK3 can also affect the MINI. But the MINI (using the official firmware) doesn't let users correct it; it only supports a single Z-adjust value, that affects all points equally.

So, my question is: why? Is this deliberate, to increase the perceived value of other models? If not, why is it taking so long to add that feature to the MINI? 

 

Posted : 23/05/2022 11:41 pm
Diem
 Diem
(@diem)
Famed Member
RE: Still no (manual) bed level correction for Prusa MINI?

You don't seem to understand. My problem isn't with the bed being level (or not).

Yes it is.  If the mesh bed levelling is not enough to compensate then the printer is out of alignment.

Cheerio,

Posted : 24/05/2022 7:21 am
RFC2549
(@rfc2549)
Active Member
Topic starter answered:
RE:

I think by now I've exceeded my ability to explain the same thing over and over again.

The issue is not the bed level, it's the sensor data. It's not that it's "not enough to compensate", it's that it's adding "compensation" when it shouldn't. 

And it's for that issue that Prusa includes this in other models:

https://help.prusa3d.com/article/bed-level-correction_2267

Why do you think they went to the trouble of implementing that? It's precisely for the situation I'm describing.

So, do you know when that specific feature will be available in the MINI?

 

This post was modified 1 month ago by RFC2549
Posted : 24/05/2022 7:40 am
cwbullet
(@cwbullet)
RE: Still no (manual) bed level correction for Prusa MINI?

I would recommend that you try the suggestions provided.  The correct suggestion is likely in the responses above.  

If not, you paid for support, use the chat.  

Posted by: @rfc2549

I think by now I've exceeded my ability to explain the same thing over and over again.

The issue is not the bed level, it's the sensor data. It's not that it's "not enough to compensate", it's that it's adding "compensation" when it shouldn't. 

And it's for that issue that Prusa includes this in other models:

https://help.prusa3d.com/article/bed-level-correction_2267

Why do you think they went to the trouble of implementing that? It's precisely for the situation I'm describing.

So, do you know when that specific feature will be available in the MINI?

 

 

--------------------
Chuck H
3D Printer Review Blog

Posted : 24/05/2022 11:52 am
fuchsr
(@fuchsr)
Noble Member
RE: Still no (manual) bed level correction for Prusa MINI?

So, do you know when that specific feature will be available in the MINI?

Not sure why you expect anyone here to be able to answer this. It's a user-to-user support forum, and while devs may occasionally stick their heads in here, they usually don't post. 

I don't have any insights into Prusa's plans whatsoever, but my gut feeling is that this is close to the bottom of their priority list, if it's on there at all. With the much smaller size of the print bed of the Mini compared to the Mk3S, MBL should be able to easily compensate for unevenness, if the Mini is properly adjusted in the XZ plane. Why that doesn't seem to be the case in your situation, no idea. Perhaps a broken PINDA sensor? Or a warped sheet (although I've never seen one). One cause of first layer issues I've experienced myself was caused by a tiny bit of debris that managed to slip under the sheet and got baked onto the heated bed. Beyond that, I'm running out of ideas. 

Again, people like @diem are just trying to help but none of us know anything about Prusa's plans. If you feel this would be a valuable feature to add, I'd head over to the Prusa github site and create a ticket for it. More likely to be seen by the folks that write that stuff than here.

 

Posted : 24/05/2022 11:52 am
RFC2549
(@rfc2549)
Active Member
Topic starter answered:
RE:
Posted by: @cwbullet

I would recommend that you try the suggestions provided.   

I already have (multiple times). Everything is as straight as I can measure it, considering the printer itself isn't completely rigid. I even measured the deflection of the printer's horizontal arm when the print head moves across it (it bends down very slightly as the head moves left) - which shouldn't make any difference, anyway, because the sensor moves down by the same amount as the nozzle.

Posted by: @fuchsr

Not sure why you expect anyone here to be able to answer this. It's a user-to-user support forum

Because some other user may have read something about it that I didn't. I don't expect to know everything every other user knows. Hence, I asked. If that bothers you, you don't need to reply. Especially if the reply is to a different question.

 

With the much smaller size of the print bed of the Mini compared to the Mk3S, MBL should be able to easily compensate for unevenness [...]

 

Again... the problem isn't that auto bed levelling isn't "compensating for the unevenness", it's that it's introducing an unevenness. That's what the "bed level correction" option is for, as described on that official Prusa page. 

Also, the MINI's print bed is 18 cm wide, versus 21 cm for the MK3S. I wouldn't call that "a much smaller size". But that's beside the point, anyway.

This post was modified 1 month ago by RFC2549
Posted : 24/05/2022 12:18 pm
SPNRmfg
(@spnrmfg)
Trusted Member
RE: Still no (manual) bed level correction for Prusa MINI?

RFC,

I feel your pain.  Sounds like we have the same exact problem.  I went as far as printing the test squares for the mk3 and looking in my mini settings only to find you can't compensate on the mini.

What fixed it for me was tightening the fudge out of the belts, and adjusting the X axis several times until it just worked. I may have even gone a micron or two overcompensating for the harsh squish on the far left back corner. I've noticed when fixing my MMU that something that shouldn't effect something else, still does.  Obviously this is due to my lack of knowledge.  I can't explain why the mesh bed leveling doesn't fix this but the squaring did, and I was thinking all the same thought you have posted above.

Hope this helps.

Posted : 24/05/2022 3:05 pm
cwbullet
(@cwbullet)
RE: Still no (manual) bed level correction for Prusa MINI?

I think you should use support.  You have gotten all of the suggestions that worked for me on my 13 Prusa printers.  They did not work for you, so maybe chat can give you a different answer.  

--------------------
Chuck H
3D Printer Review Blog

Posted : 24/05/2022 3:08 pm
misan
(@misan)
Moderator
RE:

I do own a MINI but I have not experienced that problem but I can tell you every time I contacted support with a problem they helped me solve it quite quickly, this is what they do 24/7, and they are quite experienced at doing it right. 

In my experience, it is the unexpected source of a problem what catches us. Sometimes when we do not see the problem right in front of us, some other person with a fresh view can tell us what we are failing to see.

One problem I have experienced with both MK3 and the MINI is that sometimes I have placed the steel sheet over one of the guiding screws in the back of the bed so it was tilted. The printed realized there was a problem and refused to print, leaving me puzzled until I figured it out.

So once you have checked what was suggested by other forum members to no avail, I urge you to contact support too.

This post was modified 1 month ago by misan
Posted : 24/05/2022 5:54 pm
rinkel
(@rinkel)
Trusted Member
RE:

Maybe use OctoPrint with the bedleveling mod, that will give you a visual insight into the bedleveling state.

Here is my current state

 

Another option is to go for the "Silicon bedleveling mod" 
If you search in the forum you'll find it.

I've been struggling with leveling too, but managed to squeeze the mini into the level i wanted. 

Posted : 25/05/2022 8:02 pm
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