High Temp Heated Chamber Issues

I've built a box enclosing my repstrap that gets up to 60C, and while it has greatly reduced warping on large prints, I've found another problem.

The filament heats up to 60C between the spool and the Extruder, (and in my best guess) greatly reducies the strength of the filament, leading to stripping at the hobbed pinch-wheel.

Has anybody else had a similar experience? I'm thinking I will might sheath the 1.75mm filament in 3mm tubing and maybe use an aquarium air-stone pump to provide active cooling for the filament. Perhaps this is why the commercial printers have cool air vented into the extruder head...

Since somebody is going to suggest it, lowering the chamber temp is not an acceptable solution. If anything, I would like to get it up to 70C. It's the only way (as far as anybody has suggested) to prevent warping on full sized prints in ABS.

The air pump sounds like an good idea, actually. Another idea to consider is limiting the chamber so that it encloses only the nozzle of the extruder (use a turkey bag or similar to define the upper surface of the chamber). I think the first mention of using a turkey/duck bag is in a post by Adrian. See here.

... or add extra thermoelectric coolers, which will cool the filament feeder and add heat to the chamber

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

VDX Wrote:
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> ... or add extra thermoelectric coolers, which
> will cool the filament feeder and add heat to the
> chamber

You had me thinking about design a Peltier cooled hot end, until I saw that they break down if the hot side goes above 85c

Edited 2 time(s). Last edit at 06/29/2011 07:42PM by raldrich.

... yes, common Peltiers aren't recommended for heating applications, here you have to search for high temp versions or expensive active heat pipes with fluid metal as transfer medium ...

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

Simpler is usually better, so try to avoid having to cool the filament.

one idea that comes to my mind is minizing the size of cooling chamber, basicly build it straight into the building bed, just thin walls as heaters. As heat radiates well, and the bed is moving, and heat tends to go upwards, it just might work.

A tiny fan blowing to the whole extruder assembly would probably be sufficient to keep it cool, if even that is necessary.

And maybe just try only the sheath, air can also be used as an excellent insulator, when there is no air circulation.

Maybe its the hobbed bolt and pinch bearing holding the heat as they are metal. Air cooling is very inefficient so maybe water cooling might be an idea.

Just run an inlet and outlet tube to your extruder block. The extruder could have an internal pipe structure as this is quite easy to do in a reprapped part. The voids in the part would wrap around the areas you want to cool. You could have an extra long inlet tube at the top of the extruder with a cylindrical water jacket, this would cool the filament as it enters the extruder.

You then just run the pipes to an external water tank with pump.

A car windscreen washer pump would be ideal as its 12v and very cheap, but may be noisy, but you could use an aquarium pump. The pump would run at room temperature so there are no special requirements as its drawing cold water from the tank, and if you had a large water tank, you wouldn't need any extra cooling of the fluid as 60 degrees isn't that hot to dissipate in the tank.

If you want to get fancy, you could buy a water cooling setup used in high end PC's for processor cooling and just design the extruder head.

Water cooled PC

Edited 2 time(s). Last edit at 01/20/2012 08:35AM by martinprice2004.