Old coffee machine for filament drying?!

I thought about stripping the heat-element from an old coffee machine to use it for printer-enclosure heating.

It has an attached bimetal-thermostat. But I´m not sure about the temp threshold.
If we could replace it for switching at a lower temp or bypass it and use a Triac-AC-dimmer to regulate the temp.
It could also heat up a selfmade mini oven for filament drying. We could even feed PTFE tube through the element and then slowly push/pull the filament through to dry it.

-Olaf

Edited 1 time(s). Last edit at 07/09/2015 07:55AM by o_lampe.

An incandescent light bulb and a dimmer or even a PID temperature controller/thermocouple/SSR could be used to make a simple drying oven. If you want to get fancy, mount a motor outside the enclosure and extend a shaft through the wall and put a fan blade inside the box to stir the air and equalize the temperature everywhere inside the box. Alternatively, find a table top convection oven at a thrift shop and add a temperature controller.

I'd guess the temperature and duration of heating should vary with the type of filament you're drying. Look at commercial raw plastic suppliers' data to find out suitable time/temperature profiles. Here's an example: http://www.toray.jp/plastics/en/amilan/technical/tec_007.html

It's not enough to just heat the filament up- that will drive the moisture out of the filament into the air in the box- you have to take the moisture out of the air in the box or it will end up in the plastic again. Maybe adding a cold plate inside the oven (Peltier junction?) to condense the moisture and drain it out of the box would be a good idea.

Thanks for the input!
A peltier element in a two chamber system would be ideal. They often work with 12V.
One chamber ( on top ) to dry the filament with the hot side of the peltier, the lower chamber to cool down and dehydrate the circulated air.
A simple styrofoam cool box would do the trick.

The basic question about the coffee-heater element is, if it would be possible to dry filament "on the fly" by pulling it through the heater tube?
-Olaf

The link for nylon indicates that exceeding 80-90C will "scortch" the filament, so you have to keep temperature down, but that means the moisture is driven off slower, too. I'd say for the sake of preserving the filament's properties, a long, low temperature bake is safer than a fast high temperature "fry".

Once you're dried the filament, you should store it in a sealed container with desiccant. We have one of these boxes at the makerspace and some of this rechargeable desiccant kept inside the box in an old sock. We use the box to store PLA filament. I periodically check the color of the desiccant and when it is pink, I put it in a pot on my printer's bed and heat it up for a few hours, stirring occasionally until it has turned blue again. Then I put it back into the sock and put that back in the dry box.

I don't know for sure, but I suspect that leaving the filament in a dry box for a long time (weeks) may extract the moisture as well as heating the filament for a shorter period of time.

Thanks DD,
sounds plausible.
The peltier idea has one major drawback. It takes a lot of energy
Passive drying with desiccant ( or some rice ) is much better.
-Olaf

I still think that Werner Berry's idea for using a paint pressure pot as a vacuum chamber for drying/storing filament is probably the best method that uses the least amount of energy.

Thingiverse has someone's design for a filament dryer using a 5-gallon plastic bucket and an incandescent light bulb, IIRC. I picked up the bucket and screw-on lid (and electronic digital temperature controller), but never got around to putting in the light bulb in it.....

Quote
o_lampe
Thanks DD,
sounds plausible.
The peltier idea has one major drawback. It takes a lot of energy
Passive drying with desiccant ( or some rice ) is much better.
-Olaf

I use a sealed tub with the bottom filled with silica gel. Keeps the humidity in the 20-25% range. Gets above 30%, change it out for fresh and oven dry it for several hours.

I made this, and works really good!

[forums.reprap.org]

Hmmmm... I store all my filament in a large plastic box with a dehumidifier in it, plus some Kitty Litter, and haven't had any problems.

But if I needed to dry my filament, I figure that I already have a suitable heater and controller and so on on my printer... the heated bed.

Apart from not being able to print, is there any reason not to park a reel of PLA on the heated bed and run it up to (say) 50C for a few hours?