Difficulty with Bed Leveling
I've recently upgraded my MK3S+ to an MK3.5S. The upgrade went fairly well. I've been having some issues with warping when printing 8x8 Multiboard tiles (2 stack), so I wanted to get everything dialed in as best as I can so I can move forward with my Multiboard project. I'm looking at printing somewhere around 70ish 8x8 tiles, so being able to print them in stacks without warping is pretty important. I figured doing a full bed first layer print would be a good place to start to see if/where I'm having issues with long/flat prints. Below are 3 different results.
I'm using a basically brand new Prusa smooth PEI sheet, as well as a brand new .4mm Obxidian nozzle. I've made sure to clean the bed with 91% IPA, after an initial cleaning with Dawn and warm water. I cleaned and re-greased all the rails with Prusa grease.
Initially I thought it might be an issue with my MMU, so I turned it off for the 2nd 2 prints. That didn't seem to make a difference. I played with the heights a little bit, but settled on -1.39 as looking the best overall. After the first 2 prints I thought it could be under-extrusion, but setting it to 101% only seemed to make it worse. After that, the only thing I could think of was that my belts were loose. I've never actually tightened them while I've owned the printer. I tightened the X & Y belts using the Prusa tuner app (which I'm actually rather suspect of, tbh). After doing so, I ran another test print and it was remarkably worse. Even at -1.38, it initially appeared as though the nozzle was pushing the filament, the way it typically does when the nozzle is too low. I brought it up to 1.35, but that was way too high (which I assumed would be the case). I ran another test print after that, and back at -1.39 I was seeing issues with gaps in the filament lines in similar places to my original print. Bed adhesion for all these prints has been pretty good, even when printing at -1.35. The only thing I haven't done is loosen the heat bed and retighten it. I'm fairly confident I did it correctly during the upgrade, starting in the middle, doing the 4 cardinal direction screws, then the diagonal corner screws last. I'm switching to a different brand of PLA and I'm going to run the first layer print again, but I'm doubtful that's the actual cause. Does anyone have any suggestions on what else to check? Are there any particularly good prints that can help show if something is off?
