Hotend Fan Not Running

Hello,

I have a box frame Prusa i3 that I built. Working on calibration...

I tried extruding a bit, so far so good, except I am not seeing the fan kick in. When should it start up? As soon as I turn on the heat? The fan is good and is wired to the RAMPS correctly.

I did find that I will need to reverse the extruder direction (in Marlin or just the connector), i.e. it extrudes when reversing it in Pronterface and vice-versa. I am not sure whether this has anything at all to do with the fan not running. Maybe I missed something in Marlin?

I did not want to get any heat damage, so I quickly shut off the heat and put a cold hair dryer to the hotend.

Thanks in advance! Getting closer!

It depends on when you/your slicer sends a G code to turn the fan on. Try sending a "M106 S255" to turn the fan to full power.

The hotend should not be heat damaged without a fan unless the thermistor setup isn't working right.

Reversing the extruder motor has nothing to do with the fan. Swap the connector.

That was fast, Thank You Sir! Exactly the kind of info I am looking for... Thermistor seems to be tracking temp properly, so I guess no worries there. Erring on the side of caution here. So I believe I see...the heat will be regulated by firmware/temp monitoring via thermistor; and if I understand and am guessing correctly, the fan regulates temp strictly to control and prevent [EDIT: over thinning (causing 'strings')] of filament during printing depending on flow rate and the speed of axes (?) At any rate, I have not sent any object code yet, so that must explain the inactivity. I'll try the command you suggest. I'll have to print out a list of these and post them on the wall by the bot... Thanks again!

Edited 1 time(s). Last edit at 05/11/2014 11:54PM by drastic00.

The extruder fan can do a couple things: cool/disrupt the convection around the hotend so that the filament feeding down towards the hotend doesn't soften too far up inside the extruder and cause a jam ( [reprap.org] ), and to also help cool the already extruded filament for applying more plastic ( [reprap.org] .)

Marlin does have an auto-fan feature in its advanced configuration options (See [github.com] ) but it is off by default, and the G-code is much more flexible.

Most people rely on their slicer to insert M106s into the G-code based on the plan. (For example, Slic3r's FilimentSettings/Cooling/.... )

The hot end fan is usually wired directly to 12 V and runs constantly when power is on. The fan connection you are talking about is the part fan for cooling of the printed part

Edited 1 time(s). Last edit at 05/12/2014 10:12AM by cnc dick.

I have my hotend fan connected to D9 on my RAMPS board. There is the other fan pins next to the extruder driver, yes those are constantly on. But if you don't need a part cooling fan then there's no reason why you can't use the D9 power for the hotend.

Edited 1 time(s). Last edit at 05/12/2014 01:35PM by Istale.

There is no reason to put the fan through the firmware and electronics for the hot end unless you have an extremely poor hot end .Just wire it to the 12 V into your ramps so comes on when the 12 V is powered

Edited 1 time(s). Last edit at 05/12/2014 08:31PM by cnc dick.

But I have two fans, one for my RAMPs board and one for my hot end. So one of them has to be...

Quote
Istale
But I have two fans, one for my RAMPs board and one for my hot end. So one of them has to be...

why do you say that you can put it directly to your power supply you can put it on the input feed to your ramps anywhere you have 12 V as many as you like