How often should nozzles be replaced?

I've got a Prusa I3 with a Mk8-ish (Chinese) extruder. It has a 0.4 mm nozzle, and lately I've noticed that when it extrudes in open air, the extrusion kind of curls up toward a particular direction. It's like maybe something (debris, erosion, out-of-round, ???) is causing some drag on one side of the nozzle bore and thus causing the extrusion to curl in the direction of the anomaly.

I was going to replace it on general principle, but I don't know what type the nozzle is. It has a larger bore (~3mm) than the ones I've seen and the PTFE tube from the heat break extends down into this larger bore (see photos).

So, do I need to replace it? How often do the wear out? Where do I find one like this? I think I could bore a 1.75 mm nozzle out (I have a mill and a 3mm chucking reamer) if I had to use an off-the-shelf replacement.







Edit: fixed images (f***ing google photos).

Edited 1 time(s). Last edit at 02/18/2016 07:47AM by hoxsiew.

I replace my nozzles whenever I suspect they have a problem since they are cheap. It looks like whoever designed your hotend used a nozzle designed for 3mm filament and used PTFE to convert to 1.75mm. try replacing it with another 3mm filament nozzle before you try to drill your own. The real looming problem here is that PTFE liner. PTFE breaks down eventually under high heat and really should not be going all the way through your heat block like that. It works well in the short run, but WILL eventually need to be replaced. and may cause a jam/print fail when it becomes a problem. You could also get a regular 1.75mm nozzle and just run the PTFE through the heat break and not all the way into the nozzle. This will probably last longer.

Probably would be a good idea to just replace the entire hot end with a properly designed one. You can already see discoloration and deformity on the PTFE tube.

I am interested to canvas opinion on the OP's description of filament flowing sideways when free-air extruding? Do we think that's a sign of problems? Might be a nice diagnostic check to do before a printing session, or do we think that's a red herring?

Quote
DjDemonD
I am interested to canvas opinion on the OP's description of filament flowing sideways when free-air extruding? Do we think that's a sign of problems? Might be a nice diagnostic check to do before a printing session, or do we think that's a red herring?

My brand new E3D v6 hot end has done that from the beginning. I don't think it is really much of an issue.