RepRap: Blog

this is probably one of the most common cries of anguish heard from new RepRap owners. The picture on the right shows two common modes of extruder failure. In each case, the symptom is that the filament cannot be pushed through the extruder, or requires enough force to damage the filament even when the nozzle has been removed and the barrel is hot enough for molten plastic to dribble out of it.

To find out what is going on, take the cooled extruder apart and look at the filament inside. If you can't get the filament out of the PTFE or PEEK spacer, the chances are that your spacer has got hot and the filament has bulged inside it. Use hose clamps or a metal sheath to stop the spacer from deforming. You will probably need a new one.

If you see a blob of plastic sitting directly on top of the heater barrel, you have a gap. Any space between the top of the barrel and the end of the hole that it fits into will accumulate plastic. This plastic will not all be molten, and will cause a lot of friction on the filament as it enters the barrel. Typically the extruder will run for a while, but mysteriously clog up if you let it cool and restart it. Or it may just jam solid.

The cure is to taper the top of the barrel to ensure it is driven into the PTFE or PEEK spacer, and to remove the thread from the top 1mm or so of the heater barrel. If the hole has not been tapped all the way to the end, this will let the heater barrel reach the bottom of it. It is important to clear any remaining melted filament before fitting the barrel back!

Vik :v)

Labels: extruder, fail