Heat creep: when filament softens where it should not

How heat creep works

A hotend has two parts: a hot one at the bottom, where the plastic melts, and a cold one at the top, where the filament is still solid and being pushed down. Between them is a narrow spot with little heat transfer that separates them.

If heat gets above that spot, the filament softens earlier than it should. It swells and jams in the feed tube. The extruder can no longer move it and the print stops, even though the nozzle itself is not clogged. That is why it often only shows after a longer print, not right at the start.

Why it happens

• Weak hotend cooling. The heatsink fan is not enough or is clogged with dust.
• A warm chamber. In an enclosure the air is warmer and heat is carried away less well.
• Long retraction. With every pull-back molten plastic gets higher into the cold zone.
• Slow printing with a low flow rate. At a slow pace the filament sits longer in the heated tube.

What this means for an order

For you this is more information than a task. We maintain the printers, and heat creep cannot be caused by the model or by a setting in the calculator.

It is connected to the fact that PLA in an enclosure needs good hotend cooling, or it softens too early.

How it is fixed

If you have your own printer, it helps to clean the heatsink fan, open the door, shorten the retraction or lower the temperature. We only explain here, we do not sell spare parts and we do not repair other people's printers.

You see the lead time in the calculator straight away. It is worked out from the printers' capacity.