A month ago or so when I tried to assemble the printer the first time I managed to break the brass barrel (bag 31 part 7) while trying to asseble the hot end even though I was using a torque wrench.
A couple of days ago I received some spare parts (bag 31) and tried to assemble the hot end once again. I tightened the nozzle with my torque wrench set to 3,5 Nm. The brass barrel did not break this time but I did a leak test where I put the brass parts (hot end) in a glass of water and forced air from my compressor through the brass barrel while checking for air bubbles in the water (leaks). I did see air bubbles so I tightened the nozzle a little bit more (3,7 Nm torque) and did the water test again, I did see air bubbles this time too. I decided to do a test print anyway and after printing for a couple of minutes I could see that plastic was leaking out between the heater block and nozzle (part 9 and 1 in bag 31).
There is quite possibly an inaccuracy by a few % on my torque wrench but I am not sure if I dare try to tighten the nozzle even more (I am scared to break the brass barrel again) even though I have tightened according to the instructions. Is there anything else I can do rather than wishing for the best while trying to tighten the nozzle more in small steps until I get no more air bubbles?
Apart from the hot end problem I am very pleased with the printer.
Don’t know if the compressed air test is a good test.
Pressure is most likely a lot higher and air is not comparable to PLA.
Anyway, if it is still leaking, heat the extruder to say 220-230°C and tighten just a little bit more. Do this very gently.
Yes it is leaking, not a lot but I have to remove plastic from the hot end every once in a while when printing to prevent plastic from eventually dripping down on the print.
Thanks for the advice, will try to heat the extruder and tighten a bit more when I get back home on friday. Is it preferred to set the torque wrench to say 3,8 or 3,9 Nm (as I wrote, it is tightened by 3,7 at the moment) or should I do it carefully by hand using a regular wrench?
I also managed to break the brass barrel on my first attempt despite using a torque wrench to set the torque to 3.5Nm. The torque did not reach 3.5Nm before the threaded part of the barrel sheared off completely (not just a stripped thread)!
I am waiting for a replacement part to arrive.
I am very concerned about either over tightening or under tightening when I get the new one.
I had a thought about using a thread sealant this time. Something like Blue Hylomar or Red Hermtite, which are used in automotive and aircraft engines.
I would welcome some feedback from Velleman or other users as to whether this has been tried before and/or whether it is a good idea?
Today I followed the instructions and heated the hot end to 225°C and tried to tighten the nozzle a bit more as gentle as I possibly could and yet the barrel broke once again. Feels hopeless to get a working hot end…
This happened to me both times, not just stripping the threads like you say.
And no more leaking, no more broken nozzles. Added advantages: painless switching of nozzles, far less chance of filament getting stuck (never had it with this hotend), higher temperature ability; supposed to be able to handle 400C if you find a thermocouple to measure it, but more realistically you dont have to be afraid to melt the PTFE tube above 245C, and it should have better retraction/flow control. You will need to doctor a mount for it, but thats fairly easy. Just use an aluminum plate or there is a printable mount on thingiverse.
note: you will probably want to use the stock heating element, as the E3D one is designed for 12V and at 15V will be a bit too powerful. The original one fits just fine.
As for the suggestion of sealant; I considered that too, but googling around this is not recommended for various reasons, not in the least the probability you will never be able to take it apart again for cleaning.
I received my replacement nozzle and have now successfully fitted it.
I dispensed with the torque wrench (which did not help on the last nozzle) and this time I applied a small amount of silicon sealant to the thread before tightening by feel. Using two short spanners I tightened until I felt a fairly positive “stop”. I know that may not help but I would describe it as “firmly tightened”.
The silicon was from Halfords (a UK motoring and cycling retailer) and is called Granville Silicone Sealant Clear. A 40g tube is £4.99. It says it is good to 250 Degrees C, so I do not expect any issues with PLA. Not sure about ABS though.
It is also possible to undo the nozzle and the sealant can be removed by hand (by finger nail).
I have had no issue with the nozzle leaking (yet)!