Filament won't load into the extruder: what to check

This guide is for loading new filament, before a print starts or during a filament change. It covers the filament end, nozzle temperature, each maker's load steps for the models their pages name, the filament sensor, extruder tension and the PTFE path. It routes to our other guides for anything they already cover:

Step 1: Cut and straighten the filament end

A squashed, bent or blobbed end is the first thing to fix.

• Prusa (MK4/S, MK3.9/S). "Ensure that the filament tip is cut at an approximate 45 degrees angle. The printer might struggle to load filament otherwise."
• Prusa (CORE One, CORE One L, XL, MK4/S, MK3.9/S, MK3.5/S, MINI). For a loading timeout, Prusa says to "cut the filament end at a clean 45° angle to help it feed smoothly."
• Prusa (MK2.5, MK2.5S, MK3, MK3S). Prusa's checklist says to cut the tip at 45° and "make sure that there is as little deformation as possible of the filament which is being loaded in."
• Creality (Ender-3 V3 and Ender-3 V3 Plus). "Use scissors to cut the filament at 45° and straighten it." Creality adds that "whether it is automatic feeding or manual feeding, the filament must be straightened."

On the K1, Creality says to look at the end of filament you pull out: "If there is a protrusion, replace the PTFE tube." Its example is a filament end with "a mushroom-shaped protrusion."

Step 2: Is the nozzle hot enough to load?

Each maker's load procedure below heats the nozzle as part of loading the filament.

If the previous filament needed a higher temperature, Polymaker warns that leftovers can block the new one. Its example is swapping from ABS to PLA: "If you just heat your hotend to 210°C and push PLA through, it is likely that there is still some ABS left inside." Polymaker suggests a cold pull, starting at the previous filament's temperature. Our clog diagnosis guide covers cold pulls.

Step 3: Follow your printer's load steps

Use the procedure for your model. The steps below are from each maker's page and apply only to the models named.

Prusa: MK4/S, MK3.9/S and XL

Prusa says that after a load attempt, the printer asks if the filament color is correct. "If the filament is not oozing from the nozzle at this stage, push the filament towards the extruder, and after that, select 'retry'."

Prusa: CORE One, CORE One L, XL, MK4/S, MK3.9/S, MK3.5/S and MINI

If loading takes too long, these printers show "Filament loading timed out." Prusa says the timeout "prevents damage to the extruder or gears." Its fixes include making sure the filament isn't stuck in the spool or guide tubes, cutting the end, and to "manually unload and reload the filament from the LCD Menu > Filament submenu."

Bambu Lab: P1 series

1. Insert the filament into the back PTFE tube until it reaches the extruder.
2. Select "Load" on the screen.
3. Wait until the nozzle heats to 250 ℃, then push the filament in by hand from the back.
4. If filament comes out of the nozzle, click "Done." If not, select "Retry" and repeat.

Bambu notes that on the P1 series, "Load" on the screen "will only load filament on the external spool." To feed from an AMS, you load the AMS and pick the slot in Bambu Studio or Bambu Handy.

Bambu Lab: A1 mini (external spool)

Bambu says to push the filament into the PTFE tube "until it can no longer move forward." The green indicator on the toolhead then lights up on the printer's screen. Click "Load," and "once the nozzle starts heating up to 250 ℃, manually push the filament into the toolhead again." Select "Done" once you see filament coming out, or "Retry" if you're not sure.

If you're swapping filament, finish the unload first. Bambu says that if the nozzle temperature "remains above 142°C without dropping, it indicates that there is remaining filament in the extruder, which means the unloading process is not completed."

Bambu Lab: X1 series (HMS 07FF-2000-0002-0002)

Bambu says this error occurs "if the filament never reaches the extruder when you feed the filament from the external spool holder." Its fix: "Manually feed the filament into the extruder and click the 'retry' (or 'resume' depending on the firmware version) button on the screen." If you meant to load from the AMS, Bambu says to check you didn't select the external slot ("Virtual slot") on the display by mistake.

Creality: Ender-3 V3 and Ender-3 V3 Plus

Creality's steps for a nozzle that doesn't discharge filament:

1. Check the spool isn't tangled and the filament holder is assembled correctly.
2. Cut the filament at 45°, straighten it, unlock the gear extruder and insert the filament into the feed port.
3. If you feel resistance and can't push further ("the filament is loaded about 22mm"), lock the gear extruder and use automatic feeding.
4. Or heat the nozzle to 240 degrees, straighten the filament, open the gear extruder, and feed by hand.

Creality recommends automatic feeding.

Creality: K1

Creality's feeding page says that if filament goes into the hotend by hand and extrudes, close the extruder handle, select "Auto Feed," and watch the extrusion and the extruder gears turning. If the gears don't turn during automatic extrusion, Creality says "the problem might be related to the extruder motor (or a connection board issue)" and to check the motor's wire connections.

Step 4: Is the filament sensor stopping the load?

Some printers won't load, or stop the load, based on what the filament sensor reports.

• Prusa (CORE One, CORE One L, XL): "Loading obstruction." The message reads "Filament was detected in the extruder filament sensor. Please remove it manually before proceeding." Prusa says this can happen "if filament from a previous load was not fully retracted or if a partial piece of filament remains in the path." Its fix is to open the Nextruder idler and remove the leftover piece, using needle-nose pliers or tweezers if needed, "but avoid scratching the internal parts." If it persists, check the sensor under LCD menu, Info, Sensor Info.
• Prusa (loading timeout models above). Prusa says to check for debris or grinding residue in the extruder gears or filament sensor area. If problems continue, recalibrate the sensor under LCD Menu, Control, Calibrations & Tests, Filament sensor calibration.
• Prusa (CORE One, CORE One L, XL, MK4/S, MK3.9/S, MK3.5/S, MINI): "Filament not detected." If the filament isn't inserted in the hotend, Prusa says to "load it using the Load filament function from the printer menu." If the print can continue but the sensor doesn't see the filament, Prusa says you can choose DISABLE FS, then check the sensor after the print with the printer cooled down and off.
• Bambu Lab A1 mini. Bambu's steps don't name a sensor, but say the green indicator on the toolhead lights up on the printer's screen once the filament is pushed in until it can no longer move forward. Look for it before you press "Load."

Step 5: Check the idler and drive gears

If the printer is trying to pull the filament in but it doesn't load, Prusa's MK4/S, MK3.9/S and XL pages say "there might be a hardware problem in some of the extruder components."

• Prusa MK4/S, MK3.9/S and XL. The two idler tension screws are "set to the optimal position at the factory." If they've been changed, Prusa says "the tips of the screws must be aligned with the front surface of the Idler Nut."
• Prusa loading timeout (CORE One, CORE One L, XL, MK4/S, MK3.9/S, MK3.5/S, MINI). Prusa says to open the idler to check the filament. On the CORE One, CORE One L, XL, MK4/S and MK3.9/S, lift the idler swivel. On the MK3.5/S, release the idler tension screw. On the MINI/+, loosen the tension screw.
• Prusa MK2.5, MK2.5S, MK3 and MK3S. Prusa lists a loose pulley (the drive gear set screw should sit on the flat of the motor shaft), "gummed up teeth" that need cleaning, gear misalignment with the PTFE tube, and an idler spring that is too loose or too tight.
• Creality K1. Creality says to check the extruder gear for filament debris and damage, clean debris with a soft brush, and replace the extrusion kit if the gear is damaged or deformed. That step names the K1 Max extrusion kit, so confirm the right part for your K1 model with Creality.
• Creality Ender-3 V3. Creality says to check whether the extruder gears are damaged or not flush, and to contact after-sales if they are.

Polymaker warns that an idler set too tight "can actually flatten the filament, making it too wide to feed," while one too loose lets the gear slip. If the extruder is clicking or grinding while you load, read our extruder clicking guide.

Step 6: Clear the PTFE path

• Prusa MK2.5, MK2.5S, MK3 and MK3S. Prusa says the filament should go "straight around the pulley into the hotend PTFE tube," and notes that "flexible filaments are sometimes tricky to align perfectly." For flexibles, see our TPU compatibility guide.
• Prusa MINI/+. Prusa says to "inspect visibly the Bowden PTFE tube for stuck filament."
• Creality K1. A filament end with a protrusion means "replace the PTFE tube." If the filament can't go into the hot end, Creality says to use the probe from the tool kit to push leftover debris down the extrusion channel. If it comes out through the nozzle, "retract the probe quickly" so molten filament doesn't stick to the throat tube and gear.
• Polymaker. For hotends that aren't all-metal, Polymaker says the PTFE tube should be pushed all the way down to the heater block, and that a gap there will cause at least a minor clog. It also says to check the extruder for a hidden piece of broken filament.

If the spool itself is dragging or knotted, see our tangled filament guide. Bambu AMS units have their own feeding checks in our AMS feeding problems guide.

Step 7: Clog or jam?

Creality's Ender-3 V3 page gives a quick test. Heat the nozzle to 240° ("based on filament type"), unlock the extruder gear and pull out the Teflon tube. Creality says that if the filament can be pulled out by hand, "it means that the filament is blocked in the throat." If it can't, "it means that the filament is blocked in the extruder."

Prusa's MK2.5 to MK3S article says that if none of its checks help, "there is a chance that you are dealing with a clogged nozzle, rather than Filament loading problems." For a clog, follow your maker's procedure in our clog diagnosis guide. If the jam keeps coming back in a warm room or enclosure, read our heat creep guide.

Checklist

• Filament end cut at about 45° and straightened.
• Old filament fully unloaded before loading new.
• Loading through the printer's load function, with the nozzle hot.
• Filament pushed in by hand when the steps say to.
• No leftover piece in the filament sensor area.
• Idler closed with the right tension, gear teeth clean.
• PTFE tube clear, straight and fully seated.
• Spool turns freely.
• If filament reaches the hotend but won't come out, treat it as a clog.

How this guide was checked

This is a research-based guide. We haven't reproduced these failures for it. Every step, temperature, message and menu path comes from the Prusa Research, Bambu Lab, Creality and Polymaker pages listed in the sources, retrieved on 2026-10-12. Load procedures are kept to the models each maker's page names. Read more in our editorial standards.

Print problems: what to check before you buy ↗