Proper FAN cooling extruder, PLA, or both, warping.. ?

I have some problems with warping of objects like spool holders or bigger, it happens well into the print.
Printing with PLA on a heated bed + Kepton (~65degrees) the objects stick well, but still, gets torn loose when high/massive enough.

Should the fan be blowing on extruder+PLA, - it's a small fan that blows rather good - should I shield the extruder to save energy, or direct the airflow so it minimizes cooling of the heated bed ? - or slow the fan, so it just blows a little.

What do you need the fan for?

---

Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

Andke Wrote:
-------------------------------------------------------
> Printing with PLA on a heated bed + Kepton
> (~65degrees) the objects stick well, but still,
> gets torn loose when high/massive enough.

If you are over extruding plastic (stuffed objects) then the nozzle can start to catch and sometimes pull objects off, especially if you are force cooling the PLA.

65 degrees may also be too high for some PLA's try at 60 degrees.

I'm interested if this problem for you is happening in low temperatures. - If you are printing in low ambient temperatures (below 15 degrees C) you may suffer from parts not sticking - I had exactly that problem recently.

> Should the fan be blowing on extruder+PLA, - it's
> a small fan that blows rather good - should I
> shield the extruder to save energy, or direct the
> airflow so it minimizes cooling of the heated bed
> ? - or slow the fan, so it just blows a little.

It depends on how fast you are printing and if you are building multiple objects of one at a time.

PLA likes a breeze (Fan) blowing across the built object, it helps to improve quality and with bridging, and also localised layer warp on objects being built at an outward going angle (Think of cube / heart gears).

Don't use a fan for the first 3 layers, blow it across the part not directly down onto the heated bed.

---

[richrap.blogspot.com]

is it possible that the fan causes the warping ? or too hot bed, or do the filament expand too much if too hot ?

>>Don't use a fan for the first 3 layers, blow it across the part not directly down onto the heated bed.

Do you control it manually ? - of use some automagic in SFACT to do that?

The Heated bed should combat warping, but if you are using a fan and over-cooling the bed then yes it will warp, a fan should be used to cool the printed PLA material as fast a possible or you may need to give more time to let the PLA cool before laying down the next layer if you can't use a fan to assist you.

You also don't want the fan blowing on the hot-end or your thermistor/s.

Yes, if you have the fan connected to the spare Fan output on RAMPS then you can control it in Gcode, if not you can just connect it to your PSU

And if you want to do it the hard way or if you don't have any spare outputs on your electronics you could connect a Fan via a microswitch that's mounted on your Z axis set to switch on when you reach 0.9mm (first 3 layers down) then the fan will automatically come on and help cool the print layers. - you can also mount the fan on the Z axis so it blows across the top layers of the print and not the heated bed.


Fan ON / Fan OFF Gcodes - [reprap.org]

---

[richrap.blogspot.com]

By doing this you are defeating the purpose of the heated bed.
You are blowing cold (room temperature) air onto the part and removing the heated air.
This causes no problem for short (Z) objects, but the taller the object the more adverse the effect.

---

Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

Thanks, I already control the fan by Gcode, but manually,

I tried to skip the fan, with default 185degree setting on extruder, it it's idle too long, like a few minutes, then the filament entering the "chamber" will get too hot, deformed, and stuck. It seems I need some airflow across the cooling fins on the "pipe" above the hot part.

So I need to at least have it blowing when idle...

I'll try to calibrate the extruder temp using a IR thermometer (I have one for -40+250 or so) - without a fan blowing on it - it's maybe too hot - that could also cause extra shrinking.

YES, the fan definitely helps to prevent the hot end stuck problem.

---

Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

Ok, so I guess I should experiment with some airflow on the upper cooling fins above the hotend, and less on the workplate/extruded material.

Unless the part is very small, or has big overhangs you don't need a fan blowing on the object.

If you have a heated bed you don't want air blown across the object unless the air is at the same temperature as the bed.

---

[www.hydraraptor.blogspot.com]

Thank you.
stopped air flow over the bed, have some flow over the top part of the hotend (the cooling fins) Did not try big prints with this configuration yet.

I had air blowing on *only* the cooling fin part (cool part) of this extruder. [ifeelbeta.de]

got increased problems with stuck filament, much resistance during extrusion.
Seems like I have to have some more air, and a bit bigger area ..

do any of the slicers have M106/M107 for cooling for fast/short-time layers? for instance, skein gives me cool or orbit. It'd be nice to not have to eventually slow down so significantly and use that fan more. i'm feelin' some proper forced convection

I'm using this thing: [www.thingiverse.com] and it's a really big help when printing small stuff. The upper section of part 5 of that same thing at first became a useless, formless blob even at 30 sec/layer but with the fan, had just minor irregularities at 10 sec/layer: [www.flickr.com]
Tradeoff was that this fan cools the print head enough so that printing at high speed became impossible. Fortunately it comes with a lever to shut off the fan when not needed.

I don't see how the orbit thing could ever work at all. How would you reliably start the extrusion again after the extruder has drained during the orbiting?

No heated bed for PLA no Kapton tape just glass+ pva glue.
pva is water soluble once dry so clean down is easy.
use fan on small parts to stop curling of edges (like gears).

Can you over-cool PLA print? I have read some threads about this and I was thinking of planting a large fan overhead my printer design to constantly blow cold air to the print table (not heated).

I mean these fans. They're different to tabletop fans, they create quite strong air current and are used for air duct ventilation. I've got some around for no apparent use with adjusters.

[www.nutone.ca]

Edited 1 time(s). Last edit at 08/31/2014 01:39AM by Reprint.

With PLA, the more air movement the better. It doesn't need to be over a larger area, and the best performance comes from concentrating the air so that the filament cools as fast as possible after it leaves the hotend and is laid on the part.
I've seen a few hectic air movers people have played with on PLA, and it has only ever improved the quality.

---

Realizer- One who realizes dreams by making them a reality either by possibility or by completion. Also creating or renewing hopes of dreams.
"keep in mind, even the best printer can not print with the best filament if the user is the problem." -Ohmarinus