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SO I got an 0.3mm nozzle to do some small gears, and managed to swap out the 0.5mm - but only after having to completely disassemble the hotend, clean it out, and basically start from scratch to put the new nozzle on, because I really didn't know what I was doing and couldn't find any good docs on how to do it.

I'd like to change nozzles more often. I couldn't find a HOWTO on the best way to change nozzles, other than ones that assume your old nozzle is damaged, and even then they skip some obvious steps (like whether to do it hot or cold, or even whether or not to remove the filament first)

So what's the best way to change a nozzle, assuming you want to reuse the old nozzle eventually? Is there a way to do it so as to minimize the amount of cleaning you have to do to the removed nozzle?

The easiest way is to have multiple hotend a and just swap them out.
If you want to change just a nozzle, you want to heat it up before you loosen it, but IMO it's a pain in the ass.

depends on material, if you are using abs you can use acetone to clean nozzles out, else you can heat up with lighter/torch and pick the plastic out.

Heat up nozzle to temperature of material being used.
Back out filament from hot nozzle.
Cool down. (Not really necessary if you use a socket wrench but I don't like to burn my fingers.)
Using wrench on body to hold in place put another wrench on nozzle and remove.
Install new nozzle
Heat up nozzle
Push filament into hot end
Print

I use a Black and Decker Gyro screw driver with a socket.

I assume you're talking about a stock hotend.

Easiest way to change nozzles is to upgrade the whole hotend to an e3d v6, then the nozzle change takes about 10 seconds.

(I never changed nozzles on my stock hotend so I can't compare to that)

DJ, changing the nozzle is pretty simple, but you need to be careful when doing it. Heat up the nozzle to operating temp, then power off the printer. You want the power off to ensure that you don't blow a fuse on accident when you get to the next step.

Carefully grip the flat sides of the heater block with a pair of slip-joint pliers and then remove the nozzle with a box end wrench. I don't recall the size though.

If you change to a threaded thermistor and a heater cartridge, nozzle changes can be a lot less harrowing. You don't have overly delicate wires to worry about.

On a completely unrelated note, it's nice to see that djgpp is still out there! (I'm the OpenDOS guy...)

g.