Changing a teflon tube inside a hotend, help with disassembly

Question

I have an HBot 3D 1.1 printer (it's a CoreXY style printer, newer versions are produced by ZMorph). I think that a filament guide tube inside the hotend got damaged, resulting in decreased diameter, which means I can't push the filament through it. It stops halfway through the heatsink (black marker in the attached photo).

I need some help, I'm not sure how to disassemble this type of hotend. With my Ender 3 which I have at home, I can just unscrew the nozzle since it's simply a hexagonal nut, but here it seems that the nozzle and heat block are one part and I don't think I can unscrew the heat block and the heatsink. I'm not sure what to do.

I'm sure the nozzle itself isn't clogged. I've done some cold-pulling on one end, inserted a thin wire from the other, and examined the insides with a flashlight.

Answer 1

This is an old hotend type, it is called a J-Head (see e.g. the J-Head Nozzle Mk V, I'm unsure which exact version you have). The hotend is serviceable, you can buy separate "nozzles" (with integrated heater block) for it in some e-shops. You should be able to unscrew the "nozzle" from the PEEK nozzle holder. The milled flat surfaces indicate that you can use a 13 mm or 1/2" open-end wrench to disassemble the PEEK nozzle holder.

The "nozzle":

The instruction to assemble such a hotend are:

Mk V

1. Secure the brass nozzle in a vise by the heater section.
2. Wrap a couple of turns of PTFE tape (plumbing tape) around the brass threads.
3. Screw the nozzle holder down onto the nozzle. If no flats are milled, use a pair of pliers to tighten the nozzle. The nozzle holder can be protected from the pliers by first wrapping it with a rag or paper towel. If there are flats milled, a 13 mm (1/2") open-end wrench can be used to tighten the nozzle.
4. Remove the brass nozzle from the vise.
5. Slide the PTFE liner down into the nozzle holder. The PTFE liner needs to be inserted such that the flat end is making contact with the brass and the internally tapered end is towards the top. Install the washer.
6. Screw in the hollow-lock socket set screw. Ensure that the washer stays centered while tightening this set screw. Use a piece of filament to ensure that the set screw is not too tight as the liner can become compressed and obstruct the passage. If this happens, slightly loosen the set screw.

To disassemble you need to reverse the order.

You need to ask yourself it you want to change to a newer type of hotend, but generally, these are higher, e.g. compared to a V6:

Answer 2

Not exactly the type of answer you probably want, but this hotend does not look servicable. The nozzle is usually considered a consumable part unless it's made of something like tungsten carbide, or at least steel. The nozzle is almost surely long past its useful life unless the printer was barely used, and the entire hotend has lots of design flaws like very small thermal mass and heat sink butting up against the heater block, which defeats the purpose of having a heat sink.

The right solution here is to figure out what kind of attachment it's supposed to use (dimensions of that groove mount) and buy or put together a replacement hotend.