What causes under-extrusion with certain filaments?

Change temperature, flow, and the extruder grip for the spool that is failing, and leave the spool that already prints alone. Clogs and flow are the two mechanical pages. SUNLU is the brand in the side-by-side photo.

One brand, one profile

r/FixMyPrint 12c7d7c is Hatchbox printing cleanly and SUNLU under-extruded and discolored on the same gcode. The leading comment says every filament wants a slightly different temperature and extrusion speed, and that SUNLU runs slightly hotter than Hatchbox for PLA and PLA+. A score-17 comment keeps a profile per brand and names SUNLU, Inland, and Overture. A score-8 comment says raise the weak one by five or ten degrees, then check diameter with calipers and raise flow if the filament is thin. SUNLU PLA and Hatchbox PLA both list 190–230 °C (374–446 °F) and a bed of 50–70 °C (122–158 °F). The slightly hotter SUNLU print is the comment. It is not a wider catalog cell. Stringing is the neighboring symptom when the temperature move goes too far.

Not under-extrusion

r/FixMyPrint 1py4pcc asks if the marks are under-extrusion or wet filament. The post is Bambu Basic PLA, a 0.4 mm nozzle, 220 °C (428 °F), a textured plate at 55 °C (131 °F), ironing on, and no supports. A score-19 comment says the bottom looks normal for bridges printed with no supports, and that ironing from someone else's settings will not be perfect. Bambu PLA Basic lists 190–230 °C (374–446 °F) and a bed of 35–45 °C (95–113 °F). The post's 220 °C (428 °F) is inside the nozzle. The post's 55 °C (131 °F) is above the bed. Drying is still the page when popping or a wet spool is the real complaint.

Gear, host, and a closed box

r/FixMyPrint una950 asks if a repeating sparse pattern on a CR-10, with Cura's standard profile, is humid filament. A score-33 comment says the extruder gear is off center or wobbling, so one side of the teeth grips and the other does not.

r/3Dprinting skq3dn is a spongy print while the extruder gear still advances the right length of filament. The comments this page retrieved blame a host that cannot parse gcode fast enough, including an old Raspberry Pi running OctoPrint and a Pi Zero. The original poster's own fix was not in that retrieved set.

r/3Dprinting 105by21 zipped a Creality enclosure on an Ender 5 Plus at 200 °C (392 °F) nozzle and 50 °C (122 °F) bed, and the PLA under-extruded. A score-25 comment says PLA is soft and the extruder gets hot enough to mangle it. A score-13 comment says PLA needs to cool and that the closed enclosure is for ABS or PETG. A score-9 comment names heat creep. Clogs is the page when the filament softens above the melt zone. PLA is the material hub.

Questions