Filament Jamming (PTFE)

This article explains why filament gets stuck inside the PTFE tube on the Vision Miner 22 IDEX V4 and how to prevent it. If your printer stops extruding mid-print, the extruder clicks or grinds, or you find a swollen filament plug when you pull the tube apart � the cause is almost always heat creep. Read this article to understand the mechanism and the three most common triggers.

Info: IMPORTANT: This article focuses on filament jamming (softening and expanding inside the tube due to heat). If your filament breaks (snaps cleanly) inside the PTFE tube � especially with rigid composites like carbon-filled or glass-filled materials � that is a different issue caused by mechanical stress from tight tube bends. See the Filament Breaks Inside Tube Guide instead.

Safety and Warnings

Warning: WARNING: Some diagnostic steps require the printer to be powered on (checking fan, running extrusion tests). For any step that involves touching wiring, removing parts, or working near the hotend � turn off the printer and unplug it from the power outlet first. WARNING: Wait at least 60 seconds after powering off for the capacitors to discharge. WARNING: The nozzle and heater block can exceed 400 �C (752 �F). Let the hotend cool to room temperature before touching any components near it.

1. What Is Heat Creep?

Heat creep is the main cause of filament jamming inside the PTFE tube. It occurs when heat from the hotend's melt zone travels upward � through the heatbreak and into the cold side of the hotend � and reaches the filament path above it.

Under normal operation, only the lower part of the hotend (the heater block and nozzle) is hot. The heatbreak and heatsink, cooled by the hotend fan, keep the upper section cold. This creates a sharp thermal boundary: filament stays solid until it reaches the melt zone, where it softens and flows through the nozzle.

When heat creep occurs, that boundary shifts upward. The filament starts softening too early � inside the heatbreak or even inside the PTFE tube. The softened filament expands, grips the inner walls of the tube, and forms a plug that blocks the entire path.

Signs of heat creep:

• Print starts fine but extrusion gradually weakens and stops after some time.
• Extruder motor starts clicking or skipping � it's trying to push filament but the path is blocked.
• When you pull the filament out, the tip has a visible bulge or mushroom shape � wider than the original filament diameter.

2. Cause 1 � Chamber Temperature Too High

Every material has a maximum safe chamber temperature. If the chamber exceeds it, the ambient heat adds to the hotend's own heat, pushing the thermal boundary upward and causing heat creep.

For example, ABS printed at a chamber temperature of 100 �C will very likely result in heat creep and a jam. The chamber is simply too hot for the cold side of the hotend to stay cold.

PLA is especially sensitive � it should always be printed with the top lid open and the doors open. PLA requires minimal or no chamber heating; a sealed, heated chamber will cause it to jam almost immediately.

How to prevent it:

• Check the recommended chamber temperature for your material before printing.
• For PLA: always print with the top lid and doors open.
• If you experience jamming with any material, try lowering the chamber temperature by 10�15 �C and test again.

Info: IMPORTANT: Always check the recommended chamber temperature limits for your specific material before printing in an enclosed environment. Refer to the material profile settings or the material manufacturer's datasheet.

3. Cause 2 � Hotend Cooling Fan Not Working

The heatsink fan (mounted on the cold side of the hotend) is responsible for keeping the heatbreak cool. It's the main defense against heat creep. If this fan stops spinning, spins too slowly, or is obstructed, heat will travel upward unchecked � even at normal chamber temperatures.

How to check:

1. Preheat the hotend.
2. Visually confirm the heatsink fan is spinning at full speed. You should feel airflow from the fan exhaust.
3. Check for any debris, filament strings, or obstructions blocking the fan blades.

If the fan is not spinning:

• Check the fan cable connection at the toolhead terminal block.
• Check if the fan is commanded on in the firmware. The heatsink fan should run automatically whenever the hotend is heated.
• If the cable is connected and the firmware commands it on but the fan still doesn't spin � the fan may need replacement.

4. Cause 3 � Incorrect Filament Retraction

When unloading filament � during a filament change, material swap, or manual retraction � pulling it out at too high a temperature causes the still-molten tip to drag upward through the heatbreak and into the cold zone. As it moves up, it cools unevenly, expands, and sticks to the inner walls.

This creates a plug that blocks the path for the next filament load.

Correct retraction procedure for the Vision Miner 22 IDEX V4:

1. Cool down before retracting. Drop the hotend temperature by at least 50 �C below the printing temperature. If you were printing at 300 �C, retract at 250 �C � or even 200 �C for extra safety.
2. Retract slowly. Pull the filament out slowly so it has time to cool and solidify as it moves up through the heatbreak. Fast retraction drags a long string of molten material into the cold zone before it can harden.
3. Wait for the temperature to stabilize before starting the retract command. Don't retract the moment the display shows the target � give it a few seconds.

Warning: IMPORTANT: The goal is to retract filament that is soft enough to pull out cleanly, but not so liquid that it smears and expands inside the cold zone. Dropping 50 �C or more from printing temperature hits that sweet spot for most materials.

FAQ

How do I tell if it's heat creep or a clogged nozzle?

Heat creep develops gradually � the print starts fine and gets worse over time (usually 15�60 minutes in). A clogged nozzle causes under-extrusion from the very start or immediately after a filament change. If your prints degrade as the print progresses, suspect heat creep. If the problem is instant, check the nozzle first.

Can heat creep happen with any material?

Yes, but some materials are more susceptible. PLA and other low-temperature materials jam easily in a heated chamber. High-temperature materials like PEEK or PEKK are more tolerant of chamber heat but can still experience heat creep if the fan fails or chamber temperature is excessive.

What should I do after clearing a heat creep jam?

Identify and fix the root cause (chamber temp, fan, retraction) before printing again � otherwise the jam will recur. Then run a short test print to confirm stable extrusion. For a full diagnostic path, see the Under-Extrusion Troubleshooting Guide.

Can I just increase the fan speed to prevent heat creep?

The heatsink fan on the Vision Miner 22 IDEX V4 runs at full speed by default when the hotend is heated. If the fan is already at 100% and you still get heat creep, the issue is chamber temperature or retraction � not fan speed.

Support

Vision Miner Support

• Email: support@visionminer.com
• Phone: +1 (949) 522-4422