Most people know that a microwave works by exciting water molecules, but I’m not interested in the dangers of the high voltage/current of a magnetron. I wonder what might be possible with scrap consumer drivers such as a piezo, speaker drivers, or ultrasonic inducers, preferably at a frequency outside of the core human audible spectrum.
- Would an induced vibration in an around 60°C, lightly convective environment, likely significantly increase the evaporation rate of water moisture absorbed within the filament of a spool of consumer grade 3d printing filament such as PLA, PETG, PC, TPU, or Aramid?
- Would certain frequencies likely alter performance?
There are medical applications where ultrasound is used to ablate small areas of tissue (see High Intensity Focused Ultrasound). It only works if you focus all the energy in a very small area, though. Sound is not an efficient way to heat a large mass. I would be impressed if you could warm a kilogram of plastic more than a few degrees above ambient. The waste heat coming off of your driving electronics (the amplifier, and the speaker/transducer itself) would dwarf whatever heat is generated by the sound waves hitting a target.
I am leaning this way too, but what I do not fully understand is the mechanics of moisture absorption and mobility at the molecular level along with the phase state transition of water. My intuition wants to picture little droplets moving around inside the filament. This infers that thermal contact with other molecules is a factor in transmitting heat energy into the droplets. So perhaps vibrationally moving the droplets around would promote mobility that reduces the total thermal contact and accelerates evaporation somehow.
Here is something I remember from 2 decades ago.
https://www.npr.org/2004/04/28/1861434/ben-jerrys-uses-sound-to-chill-ice-cream
They used sound to make standing waves that created areas of hot and cold, then somehow ejected the hot, keeping the cold. You’d just keep the hot and eject the cold instead.
Unless you are going to do something like Ben and Jerry’s though, all you are going to be doing with your speaker idea, as far as I can see, is to try to induce friction heat via vibration, and possibly move air around. There are easier ways to make heat than that. You may also create mechanical fatigue in the material moving it back and forth so much in the attempt to make heat, which may negatively impact the performance of the material.
As for ultrasonic humidifiers, they work by exploiting water’s ability to cavitate, as it is a liquid. If you can get plastic to cavitate somehow and emit only water vapor, without destroying the filament, that would be impressive!
A resistive heater is probably going to be a more effective means of drying filament. Personally I would just get an air fryer and run it in dehydrate mode, if I wanted to use a consumer device in an alternate manner
Just curious but is this for a side/thought experiment?
Reason I ask is cause:
why not use silica desiccants? These are fairly cheap, easy to obtain, and quite widely known in the 3D printing space.Silica is great for preventing it from getting humidified (is that the right word for this?), but if you’re trying to get the moisture out of already humidified filament it won’t really help.
Desiccants only passively absorb what is present in the air. Lowering the humidity while raising the temperature are both passively altering the environment to cause evaporation. I think induced vibration should add some additional energy regardless of the frequency, but perhaps certain harmonics will induce water moisture more than others and directly increase the energy in the specific molecule of interest. This might greatly reduce the time it takes to dry most filaments.
I have a old subwoofer from a computer speaker set I’m going to make into a filament drier. I already have the amp and power supply built in. It would be trivial to try this if it is potentially effective.
It’ll be interesting if it works, the only thing I can say is best of luck!✊
I know ultrasonic humidifiers are a thing, but I’ve never heard of using sound for materials drying. I suspect gentle heating would be far more effective. And the ultrasonic would probably degrade the material as well.
But give it a shot and see if it works.
For me, ideas and digital designs are cheap, but due to my physical disability, the motivations to harm myself by doing any physical activities are very mentally expensive.
It is rare for someone to have damaged their thoracic (ribs region) spine. Holding posture is like lift weights for me, and working with my hands is doubly so. That is what leaves me with many unfinished projects and most of these concepts abandoned long before they start. It might be different if someone can convince me that the idea has merit. Still I think it is an idea worth sharing and maybe someone else takes up the mantle of trying.
There was a tech demo (I think? It’s been a while) of an ultrasonic (clothes) dryer. They used sound waves to excite water droplets and extract them from the fabric. I don’t think it would be possible with filament.
Maybe a vacuum and gentle heating?
