Monoprice Ultimate 2 woes

Hi everyone,

I have 2 questions:

I have a Monoprice Ultimate 2 printer.

1.) Is there supposed to be some kind of little plastic tube inside of the nozzel?

And the big question:
2.) Am having issues with filament wrapping around the gears inside the extruder case. Somehow I think it is melting within the gearbox. Should I add thermal paste between the heat sink and the metal block and between the metal block on the extruder case?
Am not sure what to do.


  1. Monoprice advertises the Ultimate 2 as being capable of temperatures up to 250C, so it almost certainly has a PTFE liner.

  2. Is the extruder motor getting hot? Also, does the problem occur with a hard filament like PLA or PETG? A picture might help here.


  1. Amazon has a long PTFE one. Does that mean I have to cut it to size?
    How is it put in?
    See Amazon link below:
    Monoprice Replacement Bowden Tube/PTFE Tube for the MP Select Mini (15365 and 21711) and MP Select Mini PRO (33012) 3D Printers -

Maybe I have to get this tube put in ASAP before testing out the printer again.

  1. I already cleared the clogged gears and put it together before reading the email.
    Sorry I have no pictures of the clog

Thanks alot

I’m not familiar with the hotend design; maybe @irvshapiro can help (he’s very busy). I’d need pictures. Just be sure to cut the PTFE square.

Why do you want to replace the PTFE tube? Was there a clog?


Alan thanks for your great help.

I will cut the tube as square as possible. I’m pretty sure it goes behind the hot end. I just have to unscrew the thing.

The first time filament melted and wrapped around gearbox was my fault as I turned off the printer without letting it cool (big mistake). So after taking it all apart and cleaning the gears I unscrewed out the hot end and and found this tube there. I thought it was dried filament that had a channel within (like a lavatube ), so I threw it away. It never occured to me there was supposed to be a tube until very recently like 1 week ago.

I got my eyes set on a tube in Amazon but will have to cut it to size.

thanks again

I, too, turned off the printer once without letting the hotend cool … :frowning_face:

Good luck!

hi Alan,

Yeah the “not turning off the printer while cooling off” should be added to any 3d printer tip list.

I then noticed the mk-8 hot end is loose. So I tightened it and it seems fixed because printed the little “cat ring” and it did it without the filament melting inside the gear box. So count this as RESOLVED. thanks everyone.

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