Fans, fans, fans

Hi,

I want to mount an additional fan which blows on the filament-screw and on the extruder stepper (everything is getting quite hot these days, so that i had problems with stucking pla).

Where do i get 12V? It should blow all the time...

Thanks!

Edit: Is it possible to reduce the PWM-noise? Fan blowing at 100% cools down the nozzle...

Edited 1 time(s). Last edit at 07/31/2013 06:49AM by jfkoehle.

One of the heater wires is +12V and one of the thermistor wires is 0v. Sharing 0V might disturb the thermistor reading though. There is a spare wire allocated for a Z probe that you could use for 0V. It is one of the PP pins on the 2 way header.

The fan under the carriage shouldn't cool the nozzle even when run at 100% because the fan duct directs the air away from the heater block and the heater has plenty of spare power.

You must have PLA with a very low glass transition if the hobbed bolt is too hot. Mine is barely warm to touch when running ABS in a room at 27C. More likely you would want to cool the top of the hot end.

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[www.hydraraptor.blogspot.com]

nophead Wrote:
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> The fan under the carriage shouldn't cool the
> nozzle even when run at 100% because the fan duct
> directs the air away from the heater block and the
> heater has plenty of spare power.

I think there is some sort of "ground effect" as long as z < ~5mm. Below this height, the nozzle does not reach the specified temperature (temperature is (reads) about 10°C to low). Above this height everything is fine. As far as I can say, i did not limit the nozzle current.

Its possible to print max. 2-3 layers without the fan, after that the pla stucks at top the jhead. I'm printing the thingiverse-parts for a vertical x-axis at the moment to get more space for a hot end-fan and so on.

Black PLA from Reprapsource.com @ 197°C

Thanks for your wiring hint.

I had some problems with PLA softening at the top of the JHead which tended to happen when printing the first layer of prints with a relatively large bottom surface area - I think that the problem arose as a result of heat rising by convection and hot air "hanging around" at the top of the JHead as the first - slow print speed - layer was laid down.

What I did seems to have fixed things (famous last words so fingers crossed) - I attached a small, 25mm fan to the carriage which holds the extruder so that it blows air in a direction parallel to the heat bed, across, that is, towards the top of the JHead. I powered the fan as Nophead suggests and made a clip to fasten it in place. The only problem with this is that it tends to be rather noisy. This is probably down to me - the clip is not tight enough to stop all the vibration. Another problem is that the fan is permanently on.

What I intend to do is wire the positive connection for the fan to the permanent +12V connection used for the heater and then take the negative fan wire to the probe terminal which is not wired directly to ground but to the spare ribbon cable connector which I will take, at the Melzi end of things, to a MOSFET switch controlled by one of the spare MELZI digital I/O lines.

As I have added a Think3DPrint3D Panelolu2 board to my dibond Mendell90 kit, this is quite straightforward as the MELZI adapter board for the Panelolu2 carries two MOSFET switches - I use one of them to control my "end of print" fan.

It will then be a case of using an M42 GCode command to switch on the JHead cooling fan whenever I am using PLA - it can stay switched off when using ABS.

Alan