Question about principle of nozzle change
I was looking at the procedure for nozzle changes and was surprised that the hot end has to be heated in order to do this. Why is that? Also if you have an assembled hot end and wanted to disassemble it, could you do that cold? If not how do you do that if not installed in a printer? Inquiring minds want to know!
RE: Question about principle of nozzle change
There is a scientific value called the Coefficient of linear expansion, which is a variable value for different metals, and this causes unequal movement in different metals, e.g. Brass Aluminium steel and Stainless Steel, the action of elevating the temperature before tightening, creates a firmer seal between the Nozzle and the Heatbreak.
trying the undo the nozzle without heating, is likely to result in a broken nozzle,
Prusa have test rigs, set up, to handle many hot ends at the same time, giving the opportunity to test the heater and thermistor, whilst heating up the hot end assembly prior to tightening!
If absolutely necessary to undo the nozzle on a new hot end, you could consider heating the assembly in the oven and using heat resistant gloves to handle it whilst quickly undoing the nozzle... but the oven is unlikely to get truly hot enough, and the thermistor wiring Insulation may suffer!
you could remove the heater and thermistor before a trip to the oven, but I have never needed to undo a nozzle before the hotend was in a printer... (YET!)
regards Joan
I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK
RE: Question about principle of nozzle change
Nice summary, Joan. It's also worth noting that you can heat the hotend up without it being fully assembled into the printer. I've done this a few times. Carefully.
and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan
RE: Question about principle of nozzle change
Joan, as always the best explanations!
I would always use heat to unscrew the nozzle. Either preheat it when it's mounted or heat it with a heat gun when it's dismounted. When assembling I always use ceramic or copper paste. This prevents corrosion and cold welding. The nozzles can withstand a tightening torque of 3 nm loosely. To change (E3D hotend) you need a 16mm wrench or similar to fix the block and a 7mm socket to unsrew the nozzle. Be careful not to damage the wires of the heating element and the thermistor.
Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen.