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
  • Fuzzypyro@lemmy.worldEnglish
    8·
    3 days ago

    3 things.

    1. Wash your build plate with soap and hot water. It helps more with adhesion than you think. Do not use glue stick or any adhesives on the plate. People report that it works but I always found significantly better results with just soap and hot water on pei with materials that adhere to pei well such as pla. Masking tape with adhesives might make a difference for materials that do not stick to pei.
    2. If you are designing the part or have any time with cad then put a tiny bevel chamfer on the surface that touches the build plate. Doesn’t meet to be large. Just something. It helps with cooling shrinkage and retraction of pla on the first layers.
    3. enclosure or still air will help but are not strictly needed for pla.

    Last thing I would do is maybe adjust your z-offset. It looks like it might be experiencing some elephants foot at the bottom. I would try raising the head just by about .10. Really though that is going to be fully determined by your first layer of course.

    • fonix232@fedia.io
      4·
      4 days ago

      Re: no glue

      Indeed don’t use glue sticks - or if you must, PREHEAT the bed before applying the glue, the heat helps form an even layer you won’t really get with regular glue sticks.

      I know it’s expensive but I’ve had extremely good results with 3DLAC’s bed spray. It applies evenly, doesn’t stink like hairspray, isn’t as gunky and sticky to get rid of, and even the worst offenders against bed adhesion have printed like magic after a single coat.

      Of course none of this alleviates washing the damn thing with basic dish soap. I do spray mine afterwards with some isopropyl alcohol, but that’s mostly to speed up the drying, not to clean it.

      • Fuzzypyro@lemmy.worldEnglish
        2·
        3 days ago

        Hey OP, just so you do not waste time. I mis-spoke and told you the opposite of what you should do in the program. No bevel, I meant chamfer!

        I know it doesn’t make a lot of sense to make the surface area touching the build plate smaller but it is worth it since it provides relief from the layers above pulling when it is shrinking.

          • Fuzzypyro@lemmy.worldEnglish
            2·
            3 days ago

            Not trying to be combative here but the tests you linked further support what I was saying. A small chamfer and I really mean small will have a similar effect once rendered in gcode to a fillet. If you have access to software to generate a fillet easily that is good too. That being said I would only do it for the outer rim.

            Either way the print looks like it is warping on the lowest layers and has elephants foot which is what I suspect is the biggest issue here.

            The steps I proposed are

            1. Wash the plate to help with adhesion
            2. raise z offset just a tiny bit
            3. if possible add a chamfer
            4. if adhesion is still a issue add a brim
            • silico_biomancer@lemmy.nzEnglish
              1·
              1 day ago

              I might have misunderstood you, sorry. Do you mean a fillet or chamfer on the corners? (ie rounding as viewed from the top?) Or do you mean a chamfer such that the part’s second layer is slightly wider than the first layer?