The photo shows serious warping (or curling) of my print from my old PEI sheet which was printed on my MK4 with my old heatbed. All four of the corners warped (only the worst corner is shown).

This has been a persistent problem for the last couple of years. Smaller models printed closer to the center of the bed are fine. Only bigger prints which approach the edges of the bed curl up.

I recently upgraded my MK4 to the MK4S. While I was at it, I replaced the heatbed and I bought a new PEI sheet. And even though the sheet was brand new, I did wash it thoroughly with warm water and Dawn dish soap before using it.

After running through the full calibration and reslicing my model for the new high-flow nozzle using the latest stable release of PrusaSlicer, I reprinted it with high expectations.

Unfortunately, I was disappointed. One of the corners warped. It wasn’t quite as severe as before, so that’s a slight improvement. The corner that did warp happens to be the same one shown in the pic.

Print Settings: Prusa MK4S printer (no enclosure) 0.4 mm high-flow nozzle 0.2 mm resolution 15% infill Prusament Army Green PLA

– Edit –

Wow, there are lots of good ideas here. Thanks everyone!

The things I’m going to try (in no paticular order).

  • Covering the printer with a cardboard box or insulation sheets to see if an enclosure would help.
  • Cutting a tiny relief across the sides on the first layer.
  • Adding a brim.
  • Slow down the first layer.
  • Spraying 3DLac on the corners
  • Marafon@sh.itjust.worksEnglish
    25·
    4 days ago

    I had these types of issues a lot before I built an enclosure for my printer. It’s like night and day difference being able to keep the ambient temperature consistent throughout the print. A brim can also help with this but the enclosure is the real answer.

    • lemmyman@lemmy.worldEnglish
      4·
      4 days ago

      My mk4s is in an official prusa enclosure and I still get warp on large parts. Depending on the part I will take one or more of these additional measures, they all help:

      • apply glue to the build sheet
      • add brim (I resisted this for a long time but I gave in and it’s easily the most effective thing for parts with large flat bottoms that I can’t redesign)
      • reduce perimeters and infill%
      • redesign the part to reduce bending stiffness
      • preheat for 30-60 minutes
      • mojofrododojo@lemmy.worldEnglish
        2·
        4 days ago

        is there air moving around in the build chamber? I suggested an enclosure above, before seeing this comment. argh, that really should fix it…

        • lemmyman@lemmy.worldEnglish
          2·
          4 days ago

          I do have a circulation fan but I only turn it on for materials that want more cooling like PLA. For higher temp materials (mainly PETG but I also print some ASA, PA, PC, TPU) I keep it off. Which is a little frustrating because I got it originally to circulate air through a carbon filter for fumes from those nastier materials.