Standby Tool Management
This page should serve as a guide from builders' experiences to illustrate what has worked for managing your FDM/FFM tools during their docked (standby) state. The goal is to help builders understand how FDM materials can behave when kept at printing or standby temperatures within the hotend for an extended period of time, namely during periods where the tool is docked and waiting for its next layer.
Keeping Standby Temperatures Equal to Active Printing Temperatures
This method of managing docked tools allows you to "set and forget" standby settings, and allows you to purge the nozzle of material that's accumulated within the hotend during the docked phase by initiating a purge sequence in your _tpost_ file for your tools.
The goal of the purging cycle is to extrude all the material that has been kept at printing temperature during the dock from the hotend, and allowing fresh material to be forced into the nozzle and primed for printing a new layer with the tool. If FDM materials are kept "cooking" in the hotend for "long" periods of time (how long exactly depends on the material), the material will degrade and will no longer be printable, causing endless nozzle jams, oozing issues, and other nasty stuff to your prints (blobs, zits, nozzle collisions, etc.). You should, by trial and error for your own build, try to find a point where the purge is long enough to remove all "damaged" material from within the nozzle, and yet short enough as to not waste excess amounts of "good" filament while priming the nozzle.
E3D Standard V6 Blocks
A sample purge for a standard V6 block (from E3D or otherwise) should need about 10mm of purge material per tool change. The purge itself should be a rapid extrude move followed by a slower extrude move, which will force the unsuitable material out of the nozzle and accumulate it under the parking dock location. Then a nozzle wiping sequence should be initiated to remove this extruded material from the nozzle itself, and thereby complete the nozzle purge and prime sequence.
E3D Volcano Blocks
Due to the longer hot zone of the Volcano heater blocks, you would need to purge about 16 to 25mm of material using the same "rapid then slow" extrude approach outlined above, followed by the necessary nozzle wiping sequence.