HOW TO FIX UNDER-EXTRUSION IN 3D PRINTING

Under-extrusion happens when the printer pushes out less filament than the slicer expects. The result is gaps between lines, thin walls, weak layer bonding, and a print that looks incomplete or porous. It's one of the most common print quality issues.

Under-extrusion has many possible causes: • Clogged or partially clogged nozzle — Debris, carbonized filament, or heat creep creates a partial blockage. • Incorrect flow rate / extrusion multiplier — The slicer is telling the printer to extrude less than it should. • Worn extruder gear — The drive gear that grips the filament is worn smooth and can't push it reliably. • Filament diameter inconsistency — Cheap filament can vary in diameter, causing the printer to under-extrude in thin spots. • Temperature too low — The filament isn't melting fast enough to keep up with print speed. • Print speed too fast — The extruder can't melt and push filament fast enough. • PTFE tube friction — A kinked or worn Bowden tube adds resistance.

Start by doing a cold pull: heat the nozzle to printing temp, push filament through, then cool to 90°C (PLA) and pull firmly. This clears partial clogs. Calibrate your e-steps: mark 100 mm on your filament above the extruder, extrude 100 mm, and measure how much actually moved. Adjust your steps/mm in firmware accordingly. Increase the flow rate in your slicer by 2–5% if e-steps are correct but prints still look thin. Don't exceed 110% — if you need more, something else is wrong. Check your extruder gear: look for smooth spots or accumulated filament dust. Clean or replace if worn. Raise nozzle temperature by 5–10°C. Higher temps allow faster melting. Reduce print speed by 10–20%. Slower printing gives the hotend more time to melt filament. Check the PTFE tube for kinks, gaps, or excessive wear. Replace if needed.

Calibrate e-steps when you first set up the printer, and re-check yearly. Replace nozzles every few months if printing abrasive filaments. Keep your extruder gear clean. Use quality filament with consistent diameter (±0.02 mm tolerance).