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Fan on extruder

Posted by ElMatador 
Fan on extruder
November 01, 2011 07:30PM
I'm new to the community, although I've been lurking for the past few weeks. I'm working on building a reprap and noticed that some repraps have small fans pointing to the extruder. I was wondering what the purpose of these is. Does it have something to do with cooling the extruded pastic faster for better bridging? Thanks in advance!
Re: Fan on extruder
November 01, 2011 08:01PM
Hi ElMatador,
It depends what photos you have been looking at. Fans are used to cool the 'cold-end', (the upper part of the extruder) keeping it cool. Be careful not to let air cool the hot end though if you are designing your own.

If you see a fan cooling the printed work the it's probably a small piece that's being printed. A concentration of heat from the heater block when printing a small item can deminish print quality, hence cooling the small piece with a fan can help print quality.

You don't need a fan specifically for bridging. The software can be tuned for bridging (within Skeinforge for instance). The filament is stretched across the gap, and shrinks slightly as it cools pulling the bridged filament tight.

Hope this helps a little. Keep asking questions and enjoy your project!

Re: Fan on extruder
November 02, 2011 01:58AM
Thanks! Thats exactly what I was looking for.
Re: Fan on extruder
November 05, 2011 06:59PM
hey ElMatador,

When ever you finish your build, make sure your thermistor (or whatever temperature sensor you have) is completely insulated/covered from your fan. If your sensor is exposed and you have cool air blowing onto it, the controller will read that your hot is cooler than it actually is. For example, you want to extrude your PLA at 185 C and your thermistor is reading 185 C, but your hotend is actually around 200 C because of the, I guess you can say windchill.

Good Luck out there.

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