The version of marlin I moved from is set so that the extruder would spit out a few mm of filament while the hot end is hot, but the printer is not printing. Basically the printer is idle, and while the hot end is on and to temperature the extruder would extrude a small amount of filament every so often. I guess it is just keeping fresh melted plastic in the hot end.
Just curious if this is really necessary.
Imported from wikidot
I’ve never seen this done, and no user has ever requested this.
I don’t see how it would be necessary or useful ( and it wastes plastic ), but if somebody can explain it’s usefulness maybe it can be put on the todo list.
I was just curious.
Your machine is configured to automatically extrude a few millimeters of filament every 30 seconds if you leave it idling while hot. This is to prevent plastic from sitting hot in the nozzle too long and burning or oozing out and leaving the nozzle un-primed. For the next step, you want your nozzle hot so that the metal is fully expanded, but you don’t want any plastic coming out, so retract the plastic 10mm. Square and tram your machine.
People tend to implement ideas no matter if they are useful or not 
My first printer was a di vinci pro , there software printer a dual line of plastic at the edge of the bed to prime the nozzle. That is the ONLY thing I miss from
that printer. Is there a way to get smoothie to do this just before it prints ?
Ken
Sure, just write a few lines of Gcode to do it, and put them in your slicer at he beginning of each gcode file it produces. Very easy, this has nothing to do with Smoothie it’s all about your slicer config.