Strange extruder problems

Hi

After having my Ormerod 2 printing pretty reliably i am now faced with a strange extruder problem i currently have no idea why it is occurring:

While printing the extrusion stops and the extruder grinds into the filament leaving a cut-out in the filament.
Strange enough it is not caused by a clogged extruder nozzle as i can start printing again without cleaning the nozzle but by pushing through
the cut-out in the filament.

So if anybody has an idea why this problem is occuring i would be really happy.

Tim

I had this problem on my delta printer. The solution was to reduce the extruder stepper motor current, so that if the nozzle gets temporarily blocked e.g. due to over extrusion, the motor skips steps instead of grinding through the filament.

---

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Also check that the hobbed part is not partially clogged with plastic dust.

Dave

Thanks for the tipps so far. I have indeed raised the motor current to 1000 as i have been extruding with a 0.3 nozzle the stock 800 was a little low.
Also i have been printing several kg of material so far with this setting. So i don't think that this is the problem. After setting the extruder current back to 800
it was missing steps really fast. So i switched of the motors and turned the extruder gear by hand. The extruder was extruding (so not clogged) but i really needed
a lot of force. So i disassembled the nozzle and the top of the plastic inlay is deformed. Will post an image later. As the nozzle had some thermal stress due to
the mishap i think the plastic inlay may have deformed. I will post an image later when i have made an picture.
I have now replaced the 0.3mm nozzle with my old 0.5mm nozzle.

Tim

I don't know what's causing this problem, but I'm experiencing it also.

I haven't disassembled the nozzle yet, but when I pull out the filament that had been in the hotness, there is a bulged area near the tip -- I'm guessing that when I disasemble, it will look very much like you describe.

Did you find any solution to this, other than switching back to an old nozzle?

Quote
krolco
Did you find any solution to this, other than switching back to an old nozzle?

Well, switching back the nozzle didn't solve the problem for me but replacing the hobbed bolt. Also it looked completly fine solved the issue for me.

It might be that changing the nozzle was also one step to getting the printer back working but i am still investiating that. I don't think that having a blob
at the end when chaning filament is not critical. As long as the blob is small enough to fit through the bowden that is :-).

Tim