Diagnosing the Clog

Before fixing anything, figure out how clogged the nozzle is. There are two types:

Full Clog

  • No filament extrudes when you push it manually
  • Filament click-grinds in the extruder
  • The print starts with no filament deposition

Partial Clog

  • Filament extrudes but thin or inconsistent
  • Stream is broken or curling oddly
  • Print under-extrudes despite correct settings

The fix is different for each.

Quick Test: Manual Push

Heat the nozzle to printing temperature (210°C for PLA). Disengage the extruder gear. Push filament through the hotend by hand.

  • Smooth thick stream: Not clogged. Look for other causes.
  • Thin stream or significant resistance: Partial clog.
  • Nothing comes out: Full clog.

This 30-second test tells you what you’re dealing with.

Fix 1: Cold Pull (Atomic Pull)

Best first attempt for both partial and full clogs. Works ~70% of the time.

Procedure

  1. Heat the nozzle to normal printing temp (210°C for PLA, 240°C for PETG)
  2. Push filament through manually to clear any soft, non-clogged material
  3. Cool the nozzle to 90°C (PLA) or 100°C (PETG)
  4. Wait 30 seconds for the filament tip to solidify inside the nozzle
  5. Pull the filament out forcefully — the cooled tip drags debris out with it
  6. Inspect the pulled tip:
    • Clean smooth tip = nozzle is clear
    • Black flecks or charred bits = debris is being removed
    • Bent or torn tip = nozzle still has obstruction
  7. Repeat 3-5 times with fresh filament until the pulled tip is clean

When Cold Pulls Don’t Work

If after 5-6 cold pulls the tip is still bringing out debris (or you can’t get filament to flow at all), move to fix #2.

Fix 2: Acupuncture Needle Clean

For full clogs that survive cold pulls.

Tools

  • 0.4mm acupuncture needle ($5 on Amazon, sold for 3D printer cleaning)
  • Pliers or hemostat to hold the needle (it gets hot)

Procedure

  1. Heat the nozzle to printing temp
  2. Remove filament from the extruder
  3. Insert the needle through the nozzle from below
  4. Gently work it back and forth about 5-10mm into the nozzle
  5. Push filament through while heated to flush loosened debris
  6. Repeat as needed

Caution

Don’t force the needle. If you bend or break it inside the nozzle, you’ve made the problem worse. Apply gentle pressure only.

Fix 3: Nozzle Replacement

If cold pulls and needle clearing both fail, replace the nozzle. Brass nozzles are $1-3 each. The whole swap takes 5 minutes.

Procedure

  1. Heat the nozzle to printing temp (so threads release easily)
  2. Use two wrenches — one to hold the heater block steady, one to unscrew the nozzle
  3. Carefully unscrew the old nozzle (counterclockwise from below)
  4. Screw in new nozzle hand-tight while still hot
  5. Final tighten with wrench — snug, not tight (over-tightening cracks the heat block)
  6. Run a temperature tower to verify the new nozzle is performing

Buying Replacement Nozzles

  • Brass nozzles: $1-3, fine for PLA / PETG / ABS
  • Hardened steel: $20-30, required for CF blends and abrasive filaments
  • Plated copper: $20-40, best heat conductivity (for high-flow setups)

For most users, buy 5 brass nozzles for $10 and just swap when one acts up.

Fix 4: PTFE Liner Inspection

Some printers (Bowden setups, older Ender 3s) have a PTFE (Teflon) tube that runs inside the heat break. If this liner is damaged or melted, filament can back-flow and clog higher up.

Diagnose

  • Disassemble the hotend (remove nozzle, then heat break)
  • Inspect the PTFE liner for melting, deformation, or charring
  • If degraded, replace it

Fix

  • Replace the PTFE liner ($2-3) — must be flush against the nozzle
  • Or upgrade to an all-metal hotend ($20-50) — eliminates the PTFE issue entirely

All-metal hotends require slightly different settings (PLA needs to be retracted more carefully) but solve PTFE-related clogs permanently.

Preventing Future Clogs

1. Filter Your Filament

Use a filament dust filter ($3-10) clipped to the filament path. It catches dust, hair, and shop debris before they reach the nozzle.

2. Dry Your Filament

Wet filament degrades inside the hot nozzle, leaving carbonized residue that builds up and clogs.

See Best Filament Dryer for options.

3. Don’t Leave Filament Loaded When Idle

Filament sitting in a heated nozzle (or even a warm one) for hours degrades and creates clogs. Unload filament if the printer will sit idle for days.

4. Purge Between Material Swaps

Switching from PLA to PETG without purging can leave PLA residue in the nozzle. PETG burns at PLA temps, creating clogs.

Rule: When switching to a higher-temp material, purge at the lower material’s temp first, then heat to the new temp and purge again.

5. Replace Nozzles Periodically

Even brass nozzles wear with use. Replace every 6-12 months for casual users, every 3-6 months for heavy use, immediately if you’ve been running abrasive filaments without a hardened nozzle.

What actually fixes this
Filament Dryer
Wet filament causes stringing, popping and under-extrusion. The guides name the SUNLU S2, eSUN eBOX and PrintDry.
Find on Amazon →
Nozzle Cleaning Kit
Acupuncture needles and spare nozzles for clearing partial clogs.
Find on Amazon →
These are the categories this guide recommends. Links are affiliate searches, so you pick the listing.