I was considering this idea while pondering the question of increasing the throughput (my BfB screw extruder maxes out at 16-17mm, given this roughly matches the makerbot extruder spec, I'm suspecting that it's heating the filament which creates the speed roof). I also considered the idea of creating a larger reservoir within the heater. Possibly with a specially designed heating region. The finding from the reprap groups (mostly nophead) is that you want the heating region to be as short as possible.
The current design basically has a heating reservoir roughly the size of the filament (3mm wide and roughly 15-30mm long), this means that the heater has 45-90sq mm of heating surface. I'd guess that the majority of the heating force is directed outwards, not inwards. It either radiates out horizontally(through the insulation) or along the bottom of the extruder. The amount of energy that pumps into the heater reservour is described by
W=dT*A*C
dT is the temperature difference between the heating surface and the heated area.
A is the inside surface area of the material
C is a variable based on the materials, this is complicated but this is a constant, so it should really matter.
Electronbee, 09 Sep 2009 17:22