RE: Super weird first layer
That does look odd. Guessing this is a kit.
looks like harmonics from vibration - either you have something to loose or something too tight, how smooth were the x and y carriages before you added the belts?
RE: Super weird first layer
Both X and Y carriages where just as smooth as my other machine, so figuring its either the belts or maybe something with the extruder :-/
RE: Super weird first layer
Well I’m sorry I have no idea. It looks very odd though - going to be interested in what you eventually find out. Best if luck!
RE:
That looks a lot like the first layer I was getting after upgrading my MK3S to a MK4; kinda consistently over-extruded. I was able to "correct" for it by using the live z adjust on the printer to figure out what the best offset was and then specifying that in PrusaSlicer in the "Z-offset" input under Printer Settings > General so it "stuck".
Ultimately I took a chance and ordered a new heatsink/loadcell combo and swapped that out and now I get perfectly smooth first layers. I guess the loadcell I got in my kit may have been faulty.