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Z Height Calibration Seems to not hold between prints  

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Atrix
(@atrix)
Eminent Member
Z Height Calibration Seems to not hold between prints

I have have been having an ongoing issue where I get Z height calibrated perfectly, but I get a wildly different first layer (typically too high) when I go to print, typically immediately after running the wizard.  Similarly, I will complete a print with a great first layer, immediately start another print and it will have a first layer that is too high.  Maybe an issue with the MINDA not reading the bed height accurately?  Anyway, I am, having to restart prints on a regular basis, or run through the first layer wizard over and over.  In the end, I can usually get a good print, but the extra effort is annoying.  Any ideas?

Posted : 03/01/2020 10:03 pm
Bodo
 Bodo
(@bodo)
Estimable Member
RE: Z Height Calibration Seems to not hold between prints

Same here - although this started when I found out that my MINDA cable had that wire break issue. When P/R chat support confirmed to send a new MINDA, I repaired the MINDA cable provisionally: since then I have the same issue you described. Not sure if the repair really repaired the MINDA cable now.

Got to change the MINDA tomorrow, and see if that issue goes away.

Posted : 04/01/2020 1:44 am
Area51
(@area51)
RE: Z Height Calibration Seems to not hold between prints

Is the grub screws in the heat sink tight?

This thread may help locating the problem: Avoiding early Prusa Mini Issues + Common Issues

Have a look at my models on Printables.com 😉

Posted : 04/01/2020 1:58 am
bennydesign
(@bennydesign)
New Member
RE: Z Height Calibration Seems to not hold between prints

Hi,

I got the same problem even though I fixed the heat break/heater block/cold end  issue, tightened the grub screws, repositioned the MINDA Probe etc. pp.  

The position of the nozzle is always too high on the first print.  Then I adjust the "Live Z-hight" just a tad (0.03) in the Calibration/Settings Menu and the next time everything is fine. Is that a firmware bug? MINDA Probe not confident enough what it measured? I am puzzled .. please help!

Kinds Regards

Benjamin

 

Posted : 04/01/2020 4:50 pm
Area51
(@area51)
RE: Z Height Calibration Seems to not hold between prints

After reading this thread I noticed a similar behavior. After powering on and running First Layer Cal. I get a perfect first layer.

2. print and beyond the nozzle seems to low. I corrected the live-z by adding +0.05 and that seems to correct the height.
The height holds from now on - maybe it has to do with the layer calibration.

Not sure, what is going on...

Have a look at my models on Printables.com 😉

Posted : 05/01/2020 3:15 am
Atrix
(@atrix)
Eminent Member
Topic starter answered:
RE: Z Height Calibration Seems to not hold between prints

I have made all the changes suggested in the link above (raised hotend, tightened grub screws, clipped top zip tie on extruder, adjust probe height) .  I think it is better, but still some inconsistency in z height between prints.  Will keep an eye on it and keep this thread updated.

Posted : 05/01/2020 4:14 am
JoanTabb
(@joantabb)
Moderator
RE: Z Height Calibration Seems to not hold between prints

does the Minda probe have an integrated thermistor? like the Mk3 does?

if so, it may need calibration... !

the mk3 has an LCD menu option to calibrate the sensors...

otherwise, use the 'Old School' solution, of always raising the Extruder to the same height, before starting a print. then it is likely that your Minda will be more regular...

 

also beware that the Minda sensitivity may be different when the heatbed is heating for PETG rather than PLA...  and this may require re adjustment between filament types!

Hope this helps, regards Joan

 

 

 

I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK

Posted : 05/01/2020 12:18 pm
Area51
(@area51)
RE: Z Height Calibration Seems to not hold between prints

The Minda probe only has three wires and differs from Pinda 2. If there is a temperature compensation, it must be internal, not like MKs where the firmware corrects for temperature.

I have seen live-z height differences, printing in the same material (PETG), even when lifting z to 100 mm after each print. But it could still be a temperature problem as the first print always had a cold Minda probe.

Have a look at my models on Printables.com 😉

Posted : 05/01/2020 2:07 pm
Zane
 Zane
(@zane)
Eminent Member
RE: Z Height Calibration Seems to not hold between prints

Exact same issue for me, along with some others, I have to calibrate my z and find the right height before every print! Although it does seem to be more reliable if its been preheated for a while, not sure if that affects the minda or the bed. 

Posted : 05/01/2020 3:26 pm
Crawlerin
(@crawlerin)
Prominent Member
RE: Z Height Calibration Seems to not hold between prints

@area51

MINDA does not have temperature compensation according to this post.

Posted : 05/01/2020 6:36 pm
Atrix
(@atrix)
Eminent Member
Topic starter answered:
RE: Z Height Calibration Seems to not hold between prints

Just to follow up, this is still happening.  I am going to try and make I preheat prior to z height calibration and recording numbers to see if a pattern is present.

Posted : 06/01/2020 12:51 pm
Area51
(@area51)
RE: Z Height Calibration Seems to not hold between prints

@crawlerin
That would explain the (random) variance in z-live heights.

Now it is again wise to park the extruder in a high position to let the Minda cool off between prints, like we did with Pinda first version (without thermistor).

Anyone knows what the difference is between Pinda (first version) and Minda?

Have a look at my models on Printables.com 😉

Posted : 06/01/2020 1:22 pm
towlerg
(@towlerg)
Noble Member
RE: Z Height Calibration Seems to not hold between prints

"MINDA does not have temperature compensation according to this post."

I'm sure I read somewhere that the nozzle is preheated (175C seems to ring a bell) before leveling to circumvent temperature drift.

Posted : 06/01/2020 2:40 pm
Crawlerin
(@crawlerin)
Prominent Member
RE: Z Height Calibration Seems to not hold between prints

@towlerg

Yes it does the no-ooze 2-step warm up for probing bed at 170 degrees, then heats to operational temperature. But this drift may be from other heat sources, after the print whole area is generally warmer than when you start from cold (and it is more pronounced in enclosure).

Watching first layer is more important, which most people do anyway. The little annoyance is that new value is stored as new live-z, which in my case is usually too low when I start new print from cooled printer. 

Posted : 06/01/2020 6:01 pm
Bodo
 Bodo
(@bodo)
Estimable Member
RE: Z Height Calibration Seems to not hold between prints
Posted by: @bodo

Got to change the MINDA tomorrow, and see if that issue goes away.

I did some prints with the new MINDA, and the problem never occurred again!

Posted : 06/01/2020 6:50 pm
bennydesign
(@bennydesign)
New Member
RE: Z Height Calibration Seems to not hold between prints

@bodo

I hope that doesn't mean we all need a new MINDA probe .. 

Posted : 06/01/2020 7:29 pm
julian_bauknecht
(@julian_bauknecht)
Active Member
RE: Z Height Calibration Seems to not hold between prints

I have the same issue that the Layerhigh differs up to 0.4mm between cold start and a second print after finishing one beofe. I contacted the Support Chat because of it. There i was thold that the Minda has a Thermistor build in like the Pinda Probe, but the Buddy Board FW dosnt support it yet. Dont know how it works if the Minda only has 3 wires, but maby we just have to what for new FW. 

Posted : 24/03/2020 3:18 pm
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