I have read that leaving filament in the hotend for an extended period of time when it is at temp can cause it to burn and carbonize in the nozzle. I had a bad experience with the “stop at z” settings in cura. I was printing a vase in Tglase, and didn’t want it to print the top so I used this setting to stop before. The printer did this, however it didn’t automatically cool down the hotend like it does when the print is complete. Unknowingly, I had Tglase sitting in my hotend at 245C for about 3 hours. It clogged up my nozzle worse than I’ve ever seen. It was a real pain to clean up. Because of this I try to begin my print as soon as I am at the temperature I need, and cool it down as soon as the print is done.
I have gained a bit of experience now with single extrusion prints, and have been looking into getting into printing with a dual extruder. I am specifically interested in printing in ABS with HIPS supports. I am worried though, about having one hotend idle while printing. This seems like it will be particularly problematic with the hotend responsible for supports, as they are sparse in many prints. Is this a problem in practice? How can I minimize the risk of clogged hotends?