Howto: Change Hexagon hotend nozzle

I decided to write this howto because it’s hard to find good information aboud changing the hexagon nozzle and I read questions about that topic at least once per week here in the forum. I was breaking my nozzle during learning it the hard way, another one wrote about breaking it yesterday. I think it’s enough, time to get a clear view on it, so let’s go:

This is no official Lulzbot Howto, I’m not related to them. Also don’t blame me if it goes wrong for you, do it at your own risk! If you have questions regarding some steps, ask first and do it after you are sure you understand everything. If you need force at some step, you are doing something wrong, stop immediately!
If you work exactly as described here, there should be nearly no risk of damaging your hot end. But in worst case, you could damage the thread of the heater block, which means you need to by a new one.

Removing the old nozzle:

Step 1: Drive your print head to a good working position
Move your print head to a position where you can comfortable work on it.

Step 2: Do a cold pull aka atomic pull
You do not want to have material left in the nozzle that could leak all over the threads or you tools, so do a cold pull. Short guide: Heat the nozzle to print temperature, for example 205° for PLA. When reaching it, push a little bit of filament through the nozzle to ensure there is no air in it. Switch off the heater and let it cool down to about 90-95° (again, valid for PLA in my case). During the cool down, push a little bit on the filament to extrude by hand to ensure it’s always filled with material from time to time.
When reaching cold pull temperature, pull the filament out off the hot end. If it’s not working or snapping during this step, try again with the cold pull temperature set a little bit higher. If you get strings of filament because it’s still molten inside the nozzle, repeat with a lower temperature.
You should be able to see the inside shape of the nozzle on the cold pull like in this picture:

Step 3: Heat up and clean nozzle
Heat you nozzle up to something higher then you highest print temperature, I recommend 260°. Clean the nozzle and heater with a pieace of citchen roll.

Step 4: Loosen the heater block from the heat breake
Using a 18mm wrench, loosen the heater block from the heat breake a little bit. Be careful not to damage wires from heater! Compare the pictures above for an approximate angle. The meaning behind this is to release tension from the nozzle thread and to prevent any torque being tranfered into the fragile heat break during the next steps.

Step 5: Remove the nozzle from the heater block
Using a 18mm wrench to prevent the heater block from rotating, and a 7mm wrench to turn the nozzle, loosen the nozzle from the heater. Use a peace of citchen paper or the tweezer supplied with the printer to unscrew the nozzle completely. Be sure to place something below the nozzle to catch it, or you will damage your heat bed (or your fingers) when it comes loose!

Step 6: Clean the heater block
Clean the lower surface of the heater block with a sheet of citchen paper, be shure not to push dirt into the thread! Fold the paper 2 to 4 times to prevent your fingers from getting burnet.

Unmount of the old nozzle completed, to be continued in 2. post in a few minutes…

Mount the new nozzle

Step 1: Insert the new nozzle
With you hotend still at 260°, screw the new nozzle at least one turn into the read with your fingers. Be careful not to hurt, but don’t use tools as you may damage the thread with them. Don’t hurry, you have about 5s…

Step 2: Screw the nozzle to the heater
Screw the nozzle mostly into the thread, this is best done with the tweezers. For the last turn, to have more feeling about torque (remember: don’t apply torque!), use the 18mm and 7mm wrench as in step 5 above. Hodl the heater in position with the 18mm one. Hold the 7mm wrench as short as possible with only 2-3 fingers. Slowly turn it, until you feel the nozzle reached the heaters surface. Stop here, or you may strip the thread!

Step 3: Turning the heat break against the nozzle to “seal” the connection
This is the step that prevents leakage during your prints. Grab the hot end with your sheet of paper and screw it to the heat break. Only hand tighten, never use the 18mm wrench or I promise you will need a new hot end! Be careful not to turn the heater block too far, have a look at the heater wires. If you can’t tight it in a good position, that’s due to length tolerances of the nozzle. Don’t worry, skip to the next step and come back to this step later.
Why it won’t leak this way without any torque? Your hot end is at a temperature during this procedure that is higher then your print temperature, you remember? If your heater block gets cooler, it will shrink, pressing the heat break and the nozzle together. This prevents it from leaking.

Re-orientate the hot end to safe the heater wires

First: Be careful in this step, I consider it the most dangerous step of this howto regarding the posibility to break something.
If you recognise you can’t hand-tighten the heater block in step 3, you have to turn the heat breake inside the cooling fins. There is no thread in there, it’s only fitted together and clamped with a small screw on the back side of the cooling block.
Turn off the heater and wait until it is cooled down completely. Loosen the small screw, but don’t remove it. See the picture to know where it is:

There is a small flat area above the thread of the heat breake that goes into the heater. Grab it with a wrench, slowly rotate it a few degrees to the position you need. You might need a little bit of force, but not too much. Be careful, the heat breake is fragile! Hand thighten the small screw again. Heat up to 260° again and continue with step 3 above.
You might not have a small wrench for that like me. You can also grab the heater with the 18mm wrench and rotate it this way. It worked for me, but be careful.

i tried this procedure twice and still leaking between nozzle threads and heater. enough that i have to wipe it away every 30 mins or it drips on print.

think im going to have to try the teflon tape on the nozzle, damn leak is driving me crazy

Be aware, your hotend can reach higher temperatures than teflon can handle!

Have you checked the contact surfaces of your nozzle to your heat breake? If one of them is damaged, it has to leak. It’s also possible that you have a small peace of burnt plastic between the two parts, so you can’t screw them flat to each other.

i checked again and made sure both were very clean, still same problem.

lulzbot is currently sold out of hot end replacements so I am going to mess around with the teflon in the mean time

my research shows that teflon tape is rated to 260 C,

so hopefully it will work. everything I print only requires 245 or less. ill let you know how it goes

Good article Sebastian!
We replace many hexagon nozzles here at the shop, and this is basically the procedure. I’d add:

  • To prevents shorting of wires that can harm the RAMBO, turn off the printer when tightening and loosening the nozzle. Check the wires for breaks and shorts before turning the printer back on.

To prevent leaks, it’s more important for the ends of the threaded tubes of the heatsink and nozzle to tighten against each other inside the heater block, than for the nozzle to tighten flush against heater block’s face. I’ve attached a picture of a nozzle install that’s “ok” despite the nozzle not being tight against the heater block. This nozzle has a longer threaded tube than others, so it tightened against the heatsink tube leaving a gap between the heater block face and nozzle face.

we stock many of the component hexagon hotend parts, including the heater blocks.

the lulzbot v2 hot end kit is in backorder on your website as well. So do you recommend just replacing the heater block? out of the 3 items, (heat sink, heater block, nozzle), is it always the heater block threads that will strip and need replaceing?

im guessing you are implying that if i do a nice job of blocking the leak at the nozzle/heater interface with teflon that now it will leak out of the heater block/heat sink interface instead?


I was thinking you’d need less than the full kit, something like:
or just the component parts like the heater block and and heatsink tube

We don’t recommend teflon tape. It is not necessary to make a leak proof hexagon hotend.

This might be hard to do as I think the screw has high temp thread lock on it normally.

There is no reason to apply thread look to this small screw,there was none on mine.

Maybe not but if you look at the hotend assembly guide or a new extruder you will see thread lock on that screw now. I looked at my 4 week old extruder on my Taz 6 and it has thread lock on the screw.

Here’s how I do it. I change nozzles at least 3-4 times per week and this has never failed me. I print with many different filaments and a range of nozzles from .25 to .6.

Hello! So I was just replacing my hotend nozzle and had the tweezers around the actual hotend holding it in place when all the sudden my whole lulzbot taz 6 turned off and now will not turn back on. I am pretty sure I didn’t hit anything (although one of the ends of the tweezers was near the back towards the big red wires, but again pretty sure i didn’t pull on anything). If something were to have happened it would be compressing the wires which should not break them. Do you know what could have happened? I tried restarting my machine and when the switch is flipped to on nothing happens. Any advice would be amazing! I was trying to replace the left nozzle on the dual head V3

It sounds like you might have blown a fuse on the RAMBo board. Try swapping out the F2 and F3 fuses and see if the screen comes back to life, just make sure not to run it with the fuses swapped. If the screen does come back to life, we sell replacement fuses here:

For future reference, you never want to use anything metallic on the hotend while the machine is powered on because it can cause a electrical short back to the RAMBo board.

Sebastian - Thanks for the article. - Thanks for the tip about the nozzle NOT needing to touch the heater block. I spun the part inside the heater block down a turn, so now there is a tiny gap between the nozzle and the block. No more leaks.
Great note also about turning off the printer to avoid frying Rambo. You “can” be ok, if you’re careful.

So question, could I put in a M6 thread nozzle for 1.75mm filament and print… with 1.75 filament? Or would I need other parts sized for 1.75?