Hello fellow Zim users,
I have always had that strange problem that after printing with ABS or some other material needing high temperatures, that the nozzle used for the print would afterwards not print PLA anymore. Trying to print with PLA afterwards would make a constant clicking sound, that means loosing steps and thus not being able to extrude 100% anymore.
Changing to ABS would print fine again. Trying to print PLA with ABS temperature didn’t work either.
Trying to clean or drill the nozzle and lots of other things did not change anything to the better.
Strange enough no one else seemed to have that problem.
After a few hundret hours of printing later the ABS nozzle would start loosing steps as well and had to be replaced.
Now I opened some of these nozzles to see if exchanging the ptfe liner would get the nozzles back to printing again.
Now here is the really strange part for me. All these problematic nozzles have some melted plastic between the ptfe liner and the outer light brown tube. These residues make the diameter smaller so that the filament needs more force to be pushed through. So maybe that is why I loose steps after some while. Although I don’t understand why ABS still works while PLA does not, even when trying to print PLA with ABS temperature.
Furthermore I am unable to remove the upper part of the ptfe liner.
Any idea how to remove the upper part of the ptfe liner from the tube?
Any idea how to prevent the filament leaking outside the ptfe liner?
Greeting
3DPrintEvangelist
Nozzle problems
I had this problem once, when zeepro was still in business. They sent me two new Nozzles claiming the ptfe liner may have been cut too short.
The easiest was way to remove the liner would be to use a 3mm drill to carefully drill out the old PTFE tubing. Don´t run the drill on full speed. The slower, the better. After a few millimetres of drilling, the liner will “grab” to the drill, and you can easily pull it out.
You´ll find new PTFE tubings on ebay for a few bucks per meter. Outer diameter 4mm, inner diameter 2mm.
Push it all the way into the PEEK piece, and then cut it with a razorblade nearly flush to the surface that touches the brass nozzle.
Did that about 2 times on my ZIM an home, until I switched to standard M6 nozzles. They work as well as the Zeepro nozzles, but give you the freedom of different manifacturers, materials and sizes. (That does not mean that they might not have the same problem! Switched only 4 weeks ago)
If you want some Zeepro nozzles for spare, send me a PM.
Gents, there 2 threads on your question.
1- To unload the filament you have to haet the nozzle. Extrude slowly few millimeters and retract the filament super fast. (extrude 3mm at 20mm/s and retract 100mm at 2000mm/s)
This technique avoid blocking the filament on top od the liner
2- Passing from hot filament to cold filament is always problematic. The best way to avoid issues is to strat ectruding the PLA at the ABS heat to clean up the melt zone in the nozzle. Else the ABS residue in this zone cloggle the nozzle 
You can also over heat a little if you still have problems.
CAUTION: with this technique do not heat at higher temperature the PLA for a too long period. 2-3 min is the maximum. (after the filament burn and create something like charcoal and the nozzle get dead)