Under-extrusion occurs when the hotend cannot push out the volume of plastic commanded by the slicer, leading to weak walls, missing layers, porous surfaces, or extruder skipping.
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| symptom | cause | action |
|---|---|---|
| Extruder Clicking / Skipping | Partial clog, nozzle too cold, or flow rate too high | Perform cold pull, increase hotend temp by 10°C, lower max volumetric speed |
| Sponge-like Fragile Walls | Undersized filament diameter, incorrect flow multiplier | Calibrate extrusion multiplier (0.95–1.02), measure spool with caliper |
| Clog after 30+ minutes (Heat Creep) | Hotend cooling fan failing or enclosure too hot for PLA | Open enclosure door for PLA, replace 30mm/40mm heatsink fan |
Heat nozzle to 240°C, insert nylon or PLA, turn off heater and let cool to 90°C. Once at 90°C, forcefully pull the filament out by hand. The solidified bulb pulls out burnt carbon debris.
In OrcaSlicer / Bambu Studio, every filament has a Max Volumetric Flow cap (e.g. 12 mm³/s for standard PLA, 22 mm³/s for High-Flow). Exceeding this makes the extruder skip.
Dust, stripped filament shavings, and loose spring tension cause dual-drive gears to slip along the filament strand without feeding.
Printing PLA inside a sealed heated chamber causes the filament to soften above the heatbreak before reaching the nozzle. Always vent chamber doors for low-temperature materials.
Slow the print speed down by 50% on your machine control screen. If the clicking stops immediately, your hotend cannot melt plastic fast enough for the commanded speed. If clicking continues even at low speeds, you have a physical nozzle clog.
Most calibrated filaments sit between 0.94 and 0.98 in OrcaSlicer. Running OrcaSlicer's built-in 2-pass Flow Rate calibration coupon dials this in to within ±0.01.
Quick-reference card with exact speed, flow rate, volumetric limits, and temperatures for OrcaSlicer, Bambu Studio, and Cura.
