PLA Warping  

Warping and lifting is often a result of cool air, drafts or aircon outlets, blowing over the print and messing with the cooling ... intermittent drafts (doors opening?) are hardest to track down.

Also your print has quite a small footprint for its length; enabling a brim would help it stick.

Cheerio,

RE: PLA Warping

In my experience:

1. Clean the sheet, even if it already seems clean. Use more IPA, or for the smooth sheet, occasionally use soap and water.
2. Try raising the bed temp 5 or 10 degrees above the default 60c, but no higher than 70c. I've had success at 70c, but PLA is already soft at that temperature. I believe this helps avoid shrinkage due to cooling, and it probably also helps keep cool spots on the bed at least 60 degrees.
3. Lower the Z axis 25 microns or so. More squish results in better adhesion, as long as it's not so low it interferes with extrusion
4. Try using a makeshift enclosure to cut down on air drafts. I use the "Photo studio tent" idea sometimes - https://blog.prusa3d.com/cheap-simple-3d-printer-enclosure_7785/ . I know people say not to print PLA with an enclosure, but for difficult warping situations, I've found that it helps.

Obviously 1 & 2 are the easiest to try, especially if your current bed temp is 50c. I think that is way too low.

RE: PLA Warping

Posted by: @diem

Warping and lifting is often a result of cool air, drafts or aircon outlets, blowing over the print and messing with the cooling ... intermittent drafts (doors opening?) are hardest to track down.

Also your print has quite a small footprint for its length; enabling a brim would help it stick.

Cheerio,

I can try a brim next. I'll address the drafts below...

Posted by: @jvasileff

In my experience:

1. Clean the sheet, even if it already seems clean. Use more IPA, or for the smooth sheet, occasionally use soap and water.
2. Try raising the bed temp 5 or 10 degrees above the default 60c, but no higher than 70c. I've had success at 70c, but PLA is already soft at that temperature. I believe this helps avoid shrinkage due to cooling, and it probably also helps keep cool spots on the bed at least 60 degrees.
3. Lower the Z axis 25 microns or so. More squish results in better adhesion, as long as it's not so low it interferes with extrusion
4. Try using a makeshift enclosure to cut down on air drafts. I use the "Photo studio tent" idea sometimes - https://blog.prusa3d.com/cheap-simple-3d-printer-enclosure_7785/ . I know people say not to print PLA with an enclosure, but for difficult warping situations, I've found that it helps.

Obviously 1 & 2 are the easiest to try, especially if your current bed temp is 50c. I think that is way too low.

I'll keep working on the first layer and temp settings.

I am in the process of building a Lack table enclosure

RE:

As a general rule, PLA is the best behaved of all rigid filaments for what warping is concerned.  That said, some PLA filaments warp more than others, even within the same manufacturer. I never had any problem in this regard with regular Prusament PLA but I had some trouble with Prusament PLA blend.

Follow Diem and jvasileff advices. Besides, don’t doubt to use adhesive with large square parts where the problem is more evident. Avoid glue stick. Magigoo, 3Dlac or Laverneer work great. Printing inside an enclosure would help with drafts, but beware of surpassing 35C because heat creep/jamming might appear.

 Don’t remove the print until the bed has reached room temperature. Sometimes the finished print looks fine, but it might warp afterwards if it cools down too fast. The slower the cooling, the better.

RE: PLA Warping

PLA can suffer Heat creep, in an enclosure.
this issue is not peculiar to Prusa Printers. 
Some professional printer manufacturers advise leaving the enclosure open when printing PLA. 

regards Joan

RE: PLA Warping

OK, to update this. I just checked the slicer settings and they were 215/50 for the first layer and 210/50  for the remaining layers. Bed might be a little cool

RE: PLA Warping

Yes, 50C seems too low, specially if there’s a warping issue,  Take into account that the thermistor is located underneath the bed. There’s always a few degrees of difference between the actual temperature on top of the printing plate and the value reported by the printer’s screen. Besides, and more important, the heat is not evenly spread across the plate. It tends to be colder around the corners/edges.

For instance, you set 50C as bed temperature. On top of the plate, at the center, you’ll have maybe 46-47C while on the corners it’s 40-42C. If you used an enclosure, the difference between corners and centers would be lower, because the air inside the enclosure is isolated from the colder air of the room.

RE: PLA Warping

OK, an update:

I ran out of the white PLA so I printed this in eSUN PLA+

215/60 on first layer 210/60 on the rest. Cooling fan off for first 3 layers, ramp to 100% by 5 layers (settings attached). I also made a makeshift topless enclosure with some packing foam sheets. I really need to finish my Lack enclosure.

Results: 

Zero warping..... non on the bed, and when checked on a glass top stove, no rocking of the print. !!

Not sure what single variable fixed it, maybe a combination of many...

Thanks for the suggestions, and keep commenting......

Zero warping

RE: PLA Warping

Try hairspray!

Works wonders. 

RE: PLA Warping

Hello

To reduce PLA warping on a smooth bed:

Ensure proper bed leveling.Increase bed temperature (60-70°C).Use a print surface like BuildTak or PEI.Apply bed adhesion aids (glue stick, hairspray).Print in a draft-free environment.Orient the print strategically.Consider using a raft or brim.Control part cooling and fan speed.Use quality PLA filament.Store filament properly (dry environment).Verify correct print temperature.Encourage initial layer adhesion (gentle pressure).

Thank you.