J-Head for 3mm filament extruding very slow

Hi,

so, i build my Prusa i3 not so long ago (1 week) printing went fine until i tried to print something bigger. All of a sudden nothing came out of the hot end, the hobbed bolt was just chewing the filament... I checked everything and got to the conclusion that it was the J-Head... I tried to clean the nozzle but I can't disassemble it. When the nozzle is cold i can only push the filament as shown in the picture...not to the very end. When it's hot i can push filament by hand but it extrudes very slowly... Is it possible that it's the PTFE-s - that it's crushed? I an printing with ABS. And also, any idea how to disassemble it? I am worried that I may crush it... It doesn't go with force, is it glued?

Is this a J-head clone?
The nozzle looks to be made of aluminum, is this correct?

Here is how I unblock nozzles: [hydraraptor.blogspot.co.uk]

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[www.hydraraptor.blogspot.com]

The nozzle came with the kit from Replikeo: 3D printer Prusa Mendel i3 EiNSTeiN... It says there it's a J-Head, what variant i do not know... Yes, it's aluminum... Thanks nophead, I'll look it up.

Some aluminum grades are very soft, inspect the nozzle orifice for damage. If you're curious ask your hot end supplier what material they made the nozzle from, my guess is it's machined from the softer 6061 aluminum.

7075 is considered aircraft grade aluminum, 2024 has some properties close to mild steel, (I've machined, and designed parts with 2024, it's good stuff, don't weld it).

Experimental Light-Weight Hot End
An experimental hot-end was built with a fluted nozzle holder and an aluminum nozzle (v2). A 1.75mm liner was installed and it was sent out for testing.
With a fan, to provide cooling, this nozzle has successfully printed 1.75mm PLA.
The light-weight aluminum nozzle should be insulated in order to maintain the proper temperature.
This nozzle leaked. This was most likely due to the lack of a retainer for the 1.75mm liner.

Use an aluminum nozzle made out of a high-strength aluminum alloy, such as 2024 or 7075. This should lighten the nozzle as well as improve the thermal conductivity of the nozzle. (Depending upon the alloy, the thermal conductivity, can be more than twice that of brass and an aluminum nozzle should be around 1/3rd the weight of a brass nozzle.)
[reprap.org]