Fatter walls at around layers between support and overhang  

RE: Fatter walls at around layers between support and overhang

Looks like another incarnation of the "buldge" [sic] problem discussed extensively (without a clear solution) in:

https://forum.prusa3d.com/forum/original-prusa-i3-mk3s-mk3-how-do-i-print-this-printing-help/buldge-when-print-reaches-solid-layers/paged/18/#post-369673

Take a look there for ideas.

RE: Fatter walls at around layers between support and overhang

@fuchsr

Thanks. This is the issue I am referring to. In the past, a support agent said it is called layer shift. I don't think so.

RE: Fatter walls at around layers between support and overhang

Definitely not layer shift. Layer shift moves the whole layer a certain distance to the side. The bulge is a uniform expansion of a layer (or more) in all horizontal directions. 

RE: Fatter walls at around layers between support and overhang

@fuchsr has covered it, but here's some summary information to pull together several of the recent threads...

• From solid infill to sparse
• From sparse infill to gap fill

• Thread one - Buldge when print reaches "solid" layers.
• Thread two - Any tips to get rid of the bulge?
• Thread three - Mitigate wall bulge.

• Be sure you're not just seeing the effect of minor warping. This can really throw troubleshooting off. Rotate the print and verify the problem occurs in the same place.
• Slow down external perimeter speeds (and all speeds in general). If the nozzle is moving a bit too fast, you get slight under extrusion on some layers. These are apparent as adjacent layers print with slightly different extrusion rates. I use 25mm/s for external perimeters when appearance is important.
• Calibrate your extrusion multiplier for each filament. Any slight over or under extrusion can produce very small but noticeable variations in layers with different features (e.g. infill, gap fill, top solid infill). The closer your slicer settings match your actual printer and filament, the more accurate the gcode will be.
• Calibrate linear advance (LA) for each filament. LA adjusts the flow of filament to compensate for acceleration and deceleration. If it's not right, you may see artifacts even away from features such as bumps or hole on the same layer. In some cases, a hole on one wall causes imperfections on the far side of the print.
• Add an external perimeter if vertical walls allow it. The thicker combined perimeter allows the filament flow to even out.
• Tweak perimeter extrusion widths. The problem can appear when the slicer switches between gap fill, sparse infill, and solid or top infill. If you can find a multiple of perimeter widths that minimizes these transitions, it can work for a specific print.
• If you are the part designer, make vertical free-standing walls thicker. IME, at 1.5mm thick, the problem is less noticeable. You can try for a multiple of extrusion widths, although be aware the PrusaSlicer does some internal calculations for overlap between extrusions that can throw you off.