How should I clean my extruder when changing materials?
I often switch my print material, i.e. ABS / PLA / Wood / Flex,
How can I best clean out my extruder between them to ensure I don't contaminate my next print?
If you feel you need to clean the nozzle the best approach is a cold pull. You can perform this procedure with many printers, however, you should seek advice from your printer manufacturer before attempting this process if you have any doubts.
With the previously filament still loaded and the tool head cold:
Begin to raise the temperature of the tool to the printing temperature of the next filament you intend to load
As it begins to warm up perform any tasks you normally perform during filament unloading (open the idler, for example). You should not be fighting against the extruder drive gear or any other part of the tool during this process!
With a fair amount of pressure begin pulling on the filament
The old filament should eventually release from inside of the tool leaving the end of the filament roughly in a nice molded shape of the inside of the tool. Begin loading the next filament you intend to print and manually feed some filament through as the tool finishes heating
Anything left over from the previous filament including pigment or other residue should be stuck to the end of the filament.
You can perform cold pulls as many times as you wish by loading new filament, extruding a small amount, letting it completely cool and repeating the steps.
I typically perform cold pulls on the filament I unload by manually (by hand) pulling the filament back with a temperature setting slightly lower than typical printing temperature. Due to the lower temperature, most residual filament will stick to the filament on the way out.
Great advice. Like the instructions, I usually just set the temperature and begin pulling while it's cold. As the temperature rises the filament will generally come loose much earlier than when the printing temperature is reached. I then load the next filament and feed some through by hand when it reaches printing temperature. :)