Weak or Brittle Prints
Improve parts that break easily even though they appear to have printed correctly.
A print can look perfect but still be mechanically weak.
First consider print orientation. FDM parts are normally weaker between layers than along continuous extrusion lines.
Rotate functional parts so important forces do not pull directly across layer boundaries.
Increase the number of walls or perimeters. For many functional prints, extra walls contribute more strength than simply increasing infill.
Increase top and bottom thickness where appropriate.
Choose an infill pattern and percentage suitable for the intended load.
Make sure the nozzle temperature is high enough to produce good layer bonding.
Wet or degraded filament can also reduce strength.
Different materials have different mechanical properties. PLA is stiff but can be brittle, whereas PETG often tolerates impacts better.
For heavily loaded components, material selection may be more important than slicer settings.
Common causes: poor orientation, too few walls, low temperature, unsuitable material, under-extrusion.