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justin.m3
(@justin-m3)
Active Member
Uneven print surface

I'm having some issues with my print bed being inconsistent. When I print in the middle everything is great but as soon as I start printing to the extreme left or right or near any of the corners I get warping & bed adhesion issues. I've tried the different calibration methods and nothing seems to change the result. How can I get this more consistent? In the images below you can see the far left and right of the print are way different than the print quality in the middle.

Using prusment with the prusament preset

initial z layer height is -1.7

 

LEFT SIDE:

 

RIGHT SIDE:

Best Answer by --:

Two things. Large prints warp.  Warp adds stress on bed adhesion qualities.  Bed adhesion for PLA is affected primarily by bed cleanliness, and bed temperatures.

It is not recommended by Prusa, but folks are finding a good soap and water wash of the PC sheet is needed to get PLA to stick well.  Soap and water, alone: don't use alcohol afterwards or you'll probably just contaminate the bed again.  It's also important to heat the sheet soon after washing to help dry it completely. 

Second, for large prints that tend to warp, increasing bed temp to 70c is often helpful.  With the thicker PC sheet, even 75c. 

 

ps: your layer 1 looks a little thin. You could probably get away raising the nozzle Live-Z 25 um.

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Posted : 13/07/2019 7:19 pm
justin.m3
(@justin-m3)
Active Member
Topic starter answered:
RE: Uneven print surface

Update:

The right side lifted after 30 minutes and I had to stop the print:

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Posted : 13/07/2019 7:34 pm
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 --
(@)
Illustrious Member
RE: Uneven print surface

Two things. Large prints warp.  Warp adds stress on bed adhesion qualities.  Bed adhesion for PLA is affected primarily by bed cleanliness, and bed temperatures.

It is not recommended by Prusa, but folks are finding a good soap and water wash of the PC sheet is needed to get PLA to stick well.  Soap and water, alone: don't use alcohol afterwards or you'll probably just contaminate the bed again.  It's also important to heat the sheet soon after washing to help dry it completely. 

Second, for large prints that tend to warp, increasing bed temp to 70c is often helpful.  With the thicker PC sheet, even 75c. 

 

ps: your layer 1 looks a little thin. You could probably get away raising the nozzle Live-Z 25 um.

This post was modified 2 years ago by --
Posted : 13/07/2019 8:04 pm
justin.m3 liked
justin.m3
(@justin-m3)
Active Member
Topic starter answered:
RE: Uneven print surface

Thanks I wash it and try raising the temp a little

Any idea why the first layer isn't even across the entire print bed?

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Posted : 13/07/2019 8:35 pm
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 --
(@)
Illustrious Member
RE: Uneven print surface

Prusa's bed mesh leveling isn't perfect, they use a polynomial interpolation method that can exaggerate the errors outside the measured area, so edges of the bed become basically no-mans land.   But all of this starts with the fact the bed is not true and flat.  Small rises and dips in the bed and sheet create an uneven surface. Mesh leveling strives to compensate. 3x3 is the default, but 7x7 is better.  Make sure you've selected the 7x7 option in the Calibration menus to get the best experience.

This post was modified 2 years ago by --
Posted : 13/07/2019 9:18 pm
Patrick and justin.m3 liked
justin.m3
(@justin-m3)
Active Member
Topic starter answered:
RE: Uneven print surface

Just wanted to follow up:

I think washing was an excellent idea. there was some sort of cloudy buildup on the bed that washed away with soap. Adjusting the live-z also fixed the first layer. Printing with a bed temp of 70 worked well but there was a little warping right at the end. I adjusted to 75 for my next print and that worked really well. Is there any reason to not always print with a bed temp of 75 for PLA?

Thanks for all your help!

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Posted : 14/07/2019 7:36 pm
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(@)
Illustrious Member
RE: Uneven print surface
Posted by: justin.m3

Is there any reason to not always print with a bed temp of 75 for PLA?

Thanks for all your help!

I've wondered the same, but guessing it's probably the elephant foot problem. At 75c, the PLA is a bit mushy and may deform more than you want as you build up larger parts.  And glad the advice helped.

Posted : 14/07/2019 8:05 pm
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