I now have over 300h of printing on my DaVinci 1.0A and the extruder was starting to jam more than I was prepared to tolerate. 3D Printing is not a perfect system and clogging is expected, especially when using lower quality plastics from china (ebay). However there comes a point where getting a good print is difficult since the jams I'm experiencing cause one poor layer or a complete print failure every 1-2 prints now. I did however track down the problem.....

The DaVinci extruder, as with all extruders, has a heated nozzle where the plastic is melted for extrusion and then above this a heat sink to allow for cooling of the upper section where the solid plastic enters. On the stock extruder the heat break (the part between the hot and cold sections) is part of a larger aluminium part with a heat sink and fan.

Heatbreak

Unfortunately the way the fan is mounted does not provide very good cooling to this area and as such the upper section of the nozzle gets a little too hot during extended printing and can causes some jamming as the plastic gets sticky too far up the tube. This seems to be mostly caused by the open frame design allowing a lot of the fan airflow to be wasted and the fan not blowing directly on the heat sink. However moving the fan to allow a direct blow onto the heat sink would have it blow directly onto the print as well causing other issues. The current design is a compromise between ease of manufacture, cost and efficiency.

ExtruderFanExits

Replacing the metal frame with a simple fan shroud to direct the airflow seems like the most obvious solution so I printed and installed this -> http://www.thingiverse.com/thing:623274

NewFanShroud

This solution is much better at directing the airflow over the heat sink and therefore cooling the top area of the extruder nozzle. However this is not quiet the end of the story, this design places the airflow down over the heat sink and partly onto the print (unavoidable due to the extruder frame design). Since this not how I wanted it to be I simply refitted the fan backwards and therefore made it pull air up over the heat sink. This is NOT quiet as effective since its pulling warm air from the heat bed over the heat sink but since the temperature differential of that air and the heat sink is so great this still works well.

I have now been printing with a much lower jam rate (around 1/10 now) but I think I can do better so next up is to replace my tired stock extruder with something more fitting my needs.......now to order the E3Dv6 hotend :D

NOTE: Reversing the fan direction does require you to seal off some of the holes in the metal frame so that the fan pulls air through the heat sink and not these holes. I used Kaptop tape to seal up around the wire connectors and the large hole where the idle gear spring is.

Thanks to KDan for the fan shroud design and most of the work shown in this article.