Nozzle coming out of j-head

Hello everyone,

I just finished building my first 3d printer/reprap, a Prusa Mendel I2. I went to make my first test print today and it looks as tho during extrusion of the filament, the brass nozzle is coming right out of the PTFE body.

Im printing with 3mm white ABS filament from matterhackers.com, they recommend 230-240C to extrude, i had set my nozzle to 235 and waited until it reached temperature before i started feeding in filament.

heres a picture of what happened.



im pretty sure this isnt supposed to happen... I bought the nozzle from nwreprap.com it takes 3mm filament and has a 0.5mm extrusion orifice.

the nozzle and the ptfe body were pre assembled when it all showed up, i just put the resistor and thermistor into the nozzle.

any ideas why this would happen???

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Makerfarm Prusa 10" i3V | Ramps 1.4 | Pololu A4988 | Hexagon | Marlin 1.0.2 | Autolevel
Printrbot Simple Maker 1405 - Sold
RepRap Prusa i2 - Decommissioned

... PTFE is known for getting 'soft' when hot, so either you add a clamp around, that compresses the body around the threading, or change from PTFE to PEEK, what's more stable ...

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

good to know, thanks.

I put a metal hose clamp around the end the nozzle screws into, seems to be holding on good for now.

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Makerfarm Prusa 10" i3V | Ramps 1.4 | Pololu A4988 | Hexagon | Marlin 1.0.2 | Autolevel
Printrbot Simple Maker 1405 - Sold
RepRap Prusa i2 - Decommissioned

looks like its still coming out even with the hose clamp. What seems to be happening, is there is a small blue tube inside the j-head with a 3mm ID, i think the filament is binding inside that tube and pushing the whole tube down with the plastic, which then causes a gap and melted plastic just piles up building pressure.




is there any way i can permanently secure the nozzle inside the j-head?

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Makerfarm Prusa 10" i3V | Ramps 1.4 | Pololu A4988 | Hexagon | Marlin 1.0.2 | Autolevel
Printrbot Simple Maker 1405 - Sold
RepRap Prusa i2 - Decommissioned

I'd start again with a new j-head. I would check your thermistor too, from that close up photo it is obviously melting the insulation on the resistor so maybe it's just running way hotter than you think. If not it would have to be the worlds worst hotend to fail so quickly.

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Richmond, New Zealand
Thingiverse ~ YouTube

I don't think you need a whole new j-head, but you will need a new nozzle holder, which is $20 from the usual source.

If you're going to print with ABS, you should go with a PEEK nozzle holder, which has the higher melting point you'll need.

I did this once on a PEEK nozzle holder when my thermistor came out of its hole. I was still getting a temperature reading, but it didn't reflect the true temperature of the hot end, and it melted itself out. Something like this might be happening to you, so I'd recommend targeting a very low temperature of 100* or so, and if it doesn't appear to be getting to and staying at temp quickly, turn it off!

You could have something else wrong, too, like a mismatch between your thermistor and your firmware's thermistor table. If you have some independent way to check the temperature on your hotend and compare it to what your software reports, that would be excellent.

Good luck!

Looks like the sealant I used didn't work, I guess no matter what the PTFE is just going to soften and let anything slip out. Someone else looked at it too and suggested I replace the PTFE with a wooden dowel. Hopefully that can get me started until I buy a different hotend.

Has anyone tried a wooden hotend body before and what were the results?

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Makerfarm Prusa 10" i3V | Ramps 1.4 | Pololu A4988 | Hexagon | Marlin 1.0.2 | Autolevel
Printrbot Simple Maker 1405 - Sold
RepRap Prusa i2 - Decommissioned

... if I remember correct, then nophead did some tests years ago with oak for the body - you have to clamp it too and it tends to carbonise with time, but would work some time.

Another interesting material is soapstone/limestone, but PEEK is better machineable, so the most common replacement for PTFE ...

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

Hello,

I was looking through the reprap forum to see if anyone had any comments about J-Head nozzle failures and found this posting.

While there have been some failures, lately, I have tracked the problem down to a tooling issue with one of the machines. The failure is almost identical to what JC61990 has posted. If anybody is sure their hot-end came from me and 150% sure it wasn't from being overheated, I'll gladly replace it. Please contact me at reifsnyderb@hotmail.com.

In this case, as reported by JC61990, he states that the nozzle holder is PTFE and the picture does appear to be white and not tan. While I do not know who is making J-head hot-ends with PTFE nozzle holders, that is clearly not to spec. and will fail quickly. PEEK is required as PTFE will not handle the stresses.

Regards,

Brian

nwreprap.com will replace the hotend for free under warranty. Nwreprap no longer provide the white nozzle holders on their hot ends. The black PEEK nozzle holders have been reported to fail in the same manner but this could be for a different reason.

engineglue

I actually bought a new hot end, the printrbot ubis hotend. It's working beautifully. I'll most likely just replace the body of the hotend with a peek one, for now the ubis is getting me printing. Thanks for the help guys

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Makerfarm Prusa 10" i3V | Ramps 1.4 | Pololu A4988 | Hexagon | Marlin 1.0.2 | Autolevel
Printrbot Simple Maker 1405 - Sold
RepRap Prusa i2 - Decommissioned