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I'm printing parts for a HEVO (HyperCube Evolution CoreXY), using Colorfabb XT filament. After several successful prints. I'm having a lot of failed prints. They start off pretty well but after ~15 layers the filament starts to string and blob.

Printer details

Model: RepRap i3 Extruder: E3D 1.75 all metal hotend. Nozzle: .4 Print temp: 260°C (max. recommended). 

Steps I took to troubleshoot

  1. First I thought my nozzle was clogged. But it's not I can push the filament by hand without issues.
  2. Lowered the speed to 35 mm/s.
  3. Disabled retraction / disabled part cooling.
  4. increased the max temp with 10 % to ensure the filament flow

Printed parts that fail:

Top view printed part Note: the two parts on the left are printed in one job

Side view printed part

UPDATE 26/07 Dit a few more prints with PETG to eliminate the moisture problem. Same results.



1 Answer 1

This looks a lot like under extrusion caused by heat creep.

Heat creep is when the nozzle temperature 'creeps' up through the filament and makes it melt (a bit) and form a blob (or just widen enough to get stuck) a centimeter or two before the nozzle.

The characteristic is usually that everything works perfectly well for some quite fix amount of time, then there is severe under extrusion.


  • Lower the temperature (yes, as then the heat won't creep as much!)
  • Add a fan cooling down the cooling part of the print head

I have the same print head as you it seems (E3D 1.75 all metal) and I had heat creep when I changed the fan to a less noisy one (but also less effective).