Hot End problem

I am new to this forum and do not know if this issue has been addressed. If it has, someone please direct me to the proper post.

I have a problem with PLA oozing from my extruder nozzle and around my thermistor. As the PLA builds up it falls on and fuses to the part causing the nozzle to jump when it passes over it. I have recently replaced the thermistor and nozzle and have made them as tight as I can but I am still having the problem. Should I have coated the nozzle threads with some kind of heat resistant sealant before screwing it into the thermistor? I am also having this problem where the thermistor screws into the heat sink. I am using a TronXY X1 printer, (I think), I bought this printer several years ago and it has served me well. Last month the PLA extruder hot end carriage broke when I over tightened a retaining screw. I have been unable to find a correct replacement part so I kind of did a work around using a universal E3D V6 hot end carriage part. It works and actually seems better than the original. Any suggestions or help always appreciated.

I think we need a picture to really get an understanding of what’s happening. That said, there are threads on this forum that deal with the proper installation of nozzles.

If you have filament oozing out above the heater block, you can try this procedure to get a nozzle properly tightened up. Make sure you do it with the hotend heated up to printing temperature:

  • Tighten the nozzle up normally;
  • Loosen the nozzle 1 full turn;
  • Push the Bowden tube down into the hotend as far is it will go;
  • Tight the nozzle up again;
  • Run a test print & watch for leakage of filament coming from anywhere except the end of the nozzle. [/LIST] This technique has worked flawlessly for me.
  • Yeah, the main reason for a leaking hotend is screwing it together in cold state.

    Many people think they could just disassemble and reassemble a hotend like a toy model, but it does not work that way due to thermal expansion. You need to screw the parts together in hot state or you will get leaking at some point.

    Yep. All you need to do is consider the materials involved: brass & aluminum. Both are known for their thermal conductivity &, consequently, their thermal expansion.

    Thank you all for your input. It never occurred to me that the assembly needed to be done in a hot state. I will disassemble the hot end and reassemble it as you all have described. I was under the assumption that some kind of ealant was needed. Glad to know that the fix is simple.

    The technique of hot assembly has been around for a very long time. 1 example, from the days of horse & wagon, relates to wagon wheels. A blacksmith would create a metal hoop (circle) from flat bar stock. A carpenter would make a wooden wheel with spokes. The metal hoop would be slightly smaller (yes, smaller) than the width of the outside rim of the wheel. The hoop would be heated over a fire (often built on the ground just outside the blacksmith’s shop). The hoop would, of course, expand. When expanded enough, the hoop would be placed around the rim of the wheel. Water would then be poured over the hoop to quickly cool it, shrinking it down very tightly onto the wheel. The result was a really solid, tightly fitted wheel that would take a great deal of punishment. Also, the technique ensured that the hoop was tight enough to stay on the rim.