I've been following Jeremy's posts as we all could have these problems as well and he's taken some of the risk out of the equation.
So I become aware of that there is a PID controller for both the hotend and the heated bed.
So i ask myself whats a PID controller that I have to tune, and I turn to the Wiki: http://en.wikipedia.org/wiki/PID_controller
Under section 6 Limitations of PID control, Linearity it discusses the issue:
"For example, in temperature control, a common use case is active heating (via a heating element) but passive cooling
(heating off, but no cooling), so overshoot can only be corrected slowly – it cannot be forced downward.
In this case the PID should be tuned to be overdamped, to prevent or reduce overshoot,
though this reduces performance (it increases settling time)."
This exactly describes the hotend used in the extrusion process, it suffers from no active cooling!
So I'm wondering if there's room to add a small Peltier Heat Pump (usually mounted to a heat sink)
to the hotend ... or would a FAN blowing over the extruder hotend do the trick?
Jeremy, Do you have a fan installed that can cool the hotend, I've seen this in several peoples setups?
Also as someone pointed out in another http://buildlog.net
thread PID control could be taxing the controller that interprets the gcode.
Jeremy ,Is your PID controller a separate processor?