No extrusion despite cleanig the extrusion wheel

<p>In the beginning I had problems with extrusion when the extrusion wheel abraded the filament so much so that it clogged the wheel and resulted in under extrusion. I then removed the extrduer cover and cleaned the wheel wit a toothbrush so as not to damage it. later i found that the filament was not being extrude and after several attempts I found that the extruder wheel had moved on the shaft. After removing the wheel and inserting a 5mm diameter (internal) and 7mm long tube onto the shaft and replacing the wheel my extruder now works perfectly.</p>