Avoiding Nozzle Leaks

A common problem is plastic leaking around the nozzle.  Different websites and Wikis suggest to use Teflon tape on the threads for sealing.  That should not be needed if the parts are properly made.  The Ultimaker nozzle and brass heater barrel that I received are very well-made.

There are only two locations that can leak:  Each end of the brass barrel.  Threads do not leak, that is a symptom of a failed seal at the barrel tip.

The biggest problem is wrong assembly! The nozzle should be tightened properly against the brass barrel, not against the aluminum block.  Note, the seal is at the tip of the barrel, not in the threads.

Temporarily add a couple of lock-nuts to the barrel to allow sufficient tightening. After removing the lock-nuts, thread the barrel through the heater block and the plastic insulator.  There should be a slight space between the nozzle and the aluminum block to guarantee that the seal is proper between the nozzle tip and the barrel.

If the nozzle is not sealed against the barrel tip, plastic can leak up the threads and if the nozzle is sealed  to the heater block, the plastic can continue up through the heater block and leak on the top of the block.

Also note that if the nozzle afterwards is tightened up against the heater block, the force will microscopically pull out the barrel from the nozzle and possibly create a leak at the barrel tip.

Similarly if the peek is leaking it might be coming from a poor seal between the top of the barrel and the Bowden tube and in that case that joint should be fixed or you might be getting plugs there.

There is also a suggested fix by UM to feed a short length of ABS through the extruder and it will help to seal leaks if only PLA is used..

Note, if the nozzle or hardware is not properly sealing it might be necessary to use a sealant.  It is the old thing: Understand it Before Fixing it.

7 thoughts on “Avoiding Nozzle Leaks

  1. woot! did you really blog all of those entries in one day? good to see you blogging man. it’s much more lasting than burying good knowledge in Google Groups :-)

    One thing to mention regarding nozzle leaks – make sure you use the “ABS fix kit” that came with your printer. Took me ages to realize that that would seal up many of the usual leaks.


    • Thanks Jensa,
      Some of the entries were originally my posts to the user groups and grouped together. I also had the links available to my articles on my website.

      “ABS fix kit” ?? I never saw it or have heard about it. Is that a recent addition? I ordered mine last December.

  2. The ABS fix kit is basically just a 1 meter piece of 3mm black ABS that you run through the extruder. Since it’s more dense than the PLA, it’ll prevent those tiny PLA leaks around the printer head.


  3. we cannot seal our nozzle thread with any seal because we have to vary pressure and dye flow throgh nozzle by opening and closing the threads of nozzle so what can i do for this problem of mine?????

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