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Big changes in bed level when switching from PLA to PETG  

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Dik Harrison
(@dik-harrison)
Trusted Member
Big changes in bed level when switching from PLA to PETG

I'm noticing very big changes in my bed level when I switch from printing PLA (60c)  to printing PETG (85c).  Have to re-tram the bed and there is a significant amount of adjustment needed.  I don't remember ever having this issue before.  I'm wondering if either the bed or the frog is warping more now at the higher temp.  

The latest issue had the edges to the left and right (X) way higher than the middle.  It took a  quarter of a turn +- to adjust.

Is this common?  Have I just not seen it because I usually only print relatively small objects in PETG and this one is @170mm long

Posted : 24/03/2023 11:48 am
Diem
 Diem
(@diem)
Illustrious Member

This sometimes happens when a filament is not quite typical - maybe the pigment is affecting flow.

If the melt is unusually shiny/dull then that's also a hint - try tweaking the print temperature and it may behave.

Many of us have the odd spool marked '+5deg' or similar.

Cheerio,

Posted : 24/03/2023 5:37 pm
JoanTabb
(@joantabb)
Veteran Member Moderator
RE: Big changes in bed level when switching from PLA to PETG

I had one that was -35.

Anything above 170c was asking for trouble...

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 : 24/03/2023 7:21 pm
Dik Harrison
(@dik-harrison)
Trusted Member
Topic starter answered:
RE: Big changes in bed level when switching from PLA to PETG

My issue is with the bed being out of level when changing bed temp.  This is an un-level bed issue, I don't usually have adhesion issues, but on the rare occasion I do, it usually turns out to be a level issue.  I just can't understand why I am getting such large changes in level by increasing the bed temp.

Posted : 24/03/2023 8:16 pm
JoanTabb
(@joantabb)
Veteran Member Moderator
RE: Big changes in bed level when switching from PLA to PETG

do you have the Supa Pinda? 3 wire pinda on Mk3 series printer, or the older 4 wire pinda for the mk3 series?  

Just for interest sake, could you please do a couple of tests.... 

with the printer cold, switch on, and immediately raise the extruder to say 100mm above the buildplate, then heat the printer and do a z calibration check, 

then whilst everything is still hot, and the nozzle is very near the build plate, do another calibration check, and compare the results

is there a significant difference between the values? 

might be worth trying cold High and Hot low starts for z calibration, a couple of times. 

See if there is a thermally induced change in sensitivity? 

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 : 24/03/2023 11:05 pm
Dik Harrison
(@dik-harrison)
Trusted Member
Topic starter answered:
RE: Big changes in bed level when switching from PLA to PETG

I have an MK3 kit that I built in 2018 that has been upgraded to an MK3S but still has the old Pinda sensor.  I'll do the check later today, guess it could be a thermal sensitivity issue with the sensor.

Posted : 25/03/2023 10:05 am
Yasar
(@yasar)
Eminent Member
RE:

i had a similar problem, i use prusa.connect and there the MBL (MeshBedLeveling) showed me different values at every cold/warm start.... first i tried it with silikon mod but after that it didn't get better either. ..and now what can I say since I have new bearings in the Y carriage I have +-0.020mm deviations and that fits....i have a mks+

Posted : 25/03/2023 11:10 am
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