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Always on fan?

Posted by Sean.kennedy 
Always on fan?
October 27, 2015 06:47PM

My second discovery that I wanted to ask about was the always on fan. I have been trying, with little luck, to have the first layer of a print go down with the fan off. Any help?

I'm using cure.
Re: Always on fan?
October 28, 2015 04:50AM
Cannot be done on a Fisher unfortunately as the fan has to be on to cool down the hot end.
Only way I have found is to make the top cover of the fan duct detachable and pop it on and off manually to divert the airflow.

Edited 1 time(s). Last edit at 10/28/2015 04:53AM by floppah.
Re: Always on fan?
October 29, 2015 04:25AM
What I am currently trying that seems to work well is running a hotter first layer. On the cheapo filament I am currently struggling with it is happier with 205C on the first layer, but 195 is plenty on subsequent layers. This is with the first layer already at 4mm/s. A skirt also gets things going much better.
Re: Always on fan?
October 29, 2015 06:39AM
whats the hottest safe temp the fisher can reach?

im trying to print in carbon fiber xt-cf20.
Re: Always on fan?
October 29, 2015 07:02AM
Someone on here said they have run it at 260. I think that was onto Kapton, not direct onto the Buildtak. Can't remember for sure.
Re: Always on fan?
October 29, 2015 10:17AM
DON'T disconnect the fan. It's main function is to cool the top of the nozzle. If it's not doing this, the nozzle heats up further up than it should, increasing the pressure needed to extrude, until eventually you have a nozzle blockage. If you are having problems with sticking, remove the fan duct under the effector. This should help parts stick to the bed, as they won't be cooled so fast. However, you may have to put up with worse overhangs and bridging further up the print. Though you could always point a desk fan at the print for extra cooling.

The hot end temperature is limited by the accuracy of the thermistor, which is rated up to 300C, and the PTFE tube, which is rated to 275C, but this is in the cooling block so should be at a much lower temperature than the nozzle tip.

RepRapPro tech support
Re: Always on fan?
October 29, 2015 10:36AM
Thank you!

I will definitely follow your suggestions. And not exceed 260.

My issue was more that the material wouldn't adhere to the bed because it was cooling to fast, from the fan. But it's certainly not worth breaking the machine.
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