Random under extrusion

[tlawrence84]

Hey Guys,I'm experiencing random under extrusion on my CR-10s which then results in a blocked nozzle. When the block occurs, with the nozzle at 200c I can easily pull out the filament, and then feed it back in and continue to manually push the filament through without feeling unusual resistance.

I thought this may have been heat creep, as it occurs randomly, so I replaced the stock hotend with a genuine E3d V6, which with the machine being 2 years old I thought it was a worthwhile replacement/upgrade. I have upgraded my firmware to the latest Marlin version, taken from the Creality website, and run PID tuning.

This happens with any filament I use, whether this is cheap amazon esun filament (~£15 per kg), ProtoPasta premium, or Polyalchemy Elixir. I have tried each filament at temps of 200, 205 and 210.By randomly, this could happen almost straight away and lay down a rubbish first layer, or wait until 5hrs into the print then start missing layers. Sometimes it starts extruding normally again rather than completely blocking.

One thing I have noticed is that if I print a temperature test, the small details appear to over extrude and the nozzle digs itself into the layers it has already printed, so that the conical shape ends up warped. This might be a separate problem which I can worry about later.

Changing the nozzle worked for a large print, then the issue re-occurred. I'm wondering if the cheap filament could be leaving debris in the nozzle?I've been tinkering for over 2 weeks now and am running out of ideas! The most confusing part is that the new E3D V6 is showing exactly the same issues as when I had the stock extruder on.