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
Lots of great advice in this thread. To add to it:
Warp happens because of uneven cooling causing long straight lines of plastic to pull stronger than the bed adhesion. Sticking it to the bed better has had lots of focus in this chat. But you can also try to influence those first two parameters.
Other than breezes, Uneven cooling might be because those corners of your plate aren’t heating as efficiently—possibly they aren’t as insulated or the heating element just doesn’t reach there as strongly, causing cooler spots. The part itself may also be cooling too quickly there because of holes or channels, where a more evenly solid part might cool slower and more consistently.
My favourite hack for reliable designs though, especially if you wanted to share them and don’t want other people to worry as much about the warp, is creating relief features to address the long straight lines issue. Basically, on long lines heading into corners like you have here, a couple of centimeters from the corner, create a one layer high thin cut across the long line such that the slicer will interrupt the continuous line there. Make it as thin as you can get the slicer to register. Usually 0.1mm is sufficient. This is usually small enough that it will still end up closed over in the final part, so it won’t be apparent as an actual gap, but it will result in significantly less strain pulling on that corner.
Warping being directly proportional to long straight runs was a major educational moment for me for modeling.
Thin cuts in large flat sections and “wrinkles” in long walls have eliminated any threat of warping. You can also change the first layer fill direction to have shorter runs.
only on the first layer?
Never tried deeper, could probably do more. But first only ensures it’ll never affect the part strength. Good question, theoretically the higher layers will still pull on the end; but at least the first layer isn’t de-adhering purely because of its own horizontal shrink
This is gold
I need to make two more prints of this model. I will give the Thin Cut idea a try!