Bottom layers narrower, but OK after whole bottom is printed  

RE: Bottom layers narrower, but OK after whole bottom is printed

Does the narrow part correspond to the interior floor layers? If you've moved to a larger nozzle, you will need to reduce speeds accordingly. With a 1mm nozzle, you're going to be limited to less than 30mm/s. If you're printing at faster speeds, those thin "waist" layers likely correspond to the layers with solid infill and are being under-extruded. At the thinner walls, the extruder can keep up with the higher speeds, accounting for the smoother appearance.

The first thing I'd try is repeating the same print but dialing speed back to 50% using the front knob during the print. If that helps, you know you're on the right trail.

Most helpful would be if you'd save your part & settings off in a 3MF project file, zip it, then upload it here with the Attach file button at the bottom of the text edit box.

I've got notes on using different nozzle sizes with the Mk3 here that might be useful.

RE: Bottom layers narrower, but OK after whole bottom is printed

Without the project this is a complete guess but it's probably related to cooling.  The bottom layers are contracting due to the heat while  the walls are printed slower so cool more.  I'd have to see your original project for sure but I set up one with a 20x20x20 cube, and the settings you mention.

With 4 bottoms layers (0.2+3*0.6=2mm) and 2 or 3 perimeters to get sort of a 3mm wall  (2.2 or 3.3) the bottom is printed much faster and with far more plastic in a small area than the walls.  That's with something approaching 'normal' speed settings.  You can check after slicing using the preview and cycle through options like speed or volumetric flow rate.

If you zip up your project (project > save as to generate a 3mf with the model and all your settings inside) then zip it up so the forum will accept it we could take a look using your actual settings rather than my approximation/best guess.

RE: Bottom layers narrower, but OK after whole bottom is printed

Attaching the file. I decided to set the dimensions to match layer height and width, with the new dimensions:

x:19.8, y:19.8, z:8. wall width:2.2mm, bottom_wall_width: 3.2mm

I already tried lowering the temperature (nozzle and bed) but the same results and I think that speed settings are ok.

I also test with a raft of 4 layers, and the same result. The raft was OK but when the cube started to print, I got the same results.

I saw that the bottom is printed faster, so I will try to work on that (not so sure what to change, I limited the max. print speed but there were no changes)

cube_dimensions_set_proper-19.8x19.8x8-2.2mm-3.2mmBtt.3mf

cube.gcode.scad

Thanks for the help!

RE: Bottom layers narrower, but OK after whole bottom is printed

People, you are wise.

Thanks! I figure it out. I disabled the "Enable auto cooling" feature under filament, and now is working like a charm

Thanks a lot! (BTW, I switched recently from Cura to PrusaSlicer - so far is great - and I am liking it more)