As I said in another forum, I've actually had my Kickstarter Robo3D for quite a while now, but due to a lack of time, I haven't had a chance to actually set it up and use it until just recently, and the first order of business has been to upgrade all the software and then start printing hardware upgrades and mods for the printer itself.. I'm about to print a fan duct for the extruder fan, but here's my question- what is this fan supposed to be cooling? Perhaps I don't understand the concept, and if so, please correct me.. The duct design I'm looking at points the airstream at the nozzle end, but thinking about the design of hot ends and their limitations and why people have been going with all-metal hot-ends seems to be the issue of the interface with the "cold" part of the extruder and heat migration softening the "cold" parts and causing leaks, etc. Now I suppose by cooling the tip of the nozzle, you do bring down the overall temperature, but I've had a couple of lamination failures in printed objects, which led me to turn the temperature up vs. the default print settings, and my gut says that I really do not want to cool the product that's coming out of the nozzle, but instead aim the airstream higher up to try to create a nice sharp hot/cold transition just *above* the heater block.. During "break-in" and tuning, I had the hot-end running as high as 240C without the fan and just with the dissipation to ambient air and the PWM control, the temperature never varied more than a degree, so other than trying to keep the temperature of the overall extruder under control so that the "cold" parts don't start melting, I'm not clear on what the fan is actually doing and where the airflow should point, and why?