Vapor polishing is nothing new. Experienced 3D printing enthusiasts are well aware that you can smooth the surface of 3D printed objects by exposing them to the right solvents. There are a few existing methods for doing this, but each of them comes with unique drawbacks.
What's needed is a better solvent application method, and that's what this instructable is about. (Be sure to check out the video in the last step!)
The current vapor polishing methods and their drawbacks include:
1. Hot treat via boiling solvent in a crock pot or similar chamber (Potentially dangerous and very hands-on process)
2. Cold treat via slow release of solvent from paper towels in an enclosed container (Very time consuming, can't observe parts during this process.)
3. Spray canned solvent aerosol onto part. (Inconsistent surface finish, must be done outside)
4. Dipping parts directly into liquid solvents (Unpredictable/inconsistent finish, Likely over exposure of part)
All I wanted is a machine that lets me quickly drop parts into a transparent container and be able to press 'go' and have the machine produce a predictable finish on its own. I do not want to have to put together a really involved setup that may be a fire hazard, fume hazard, or something that produces unpredictable surface finishes. Essentially I want something as convenient as a microwave. I'm also forgetful so I don't want my parts to be destroyed if I forget that I left them in the machine.
The Ultrasonic Misting 3D Vapor Polisher is the solution to all of these problems.
This key component of this machine comes from ultrasonic humidifier, which uses a piezoelectric transducer (like a speaker) to create a high frequency mechanical oscillation in a liquid. This vibration forms an extremely fine mist of droplets in a fog/mist. The density of the fog is controlled by varying the intensity of the vibrations via a potentiometer.
This fog mist is very dense and wont move far on its own, so I used an aquarium air pump to blow it from the misting chamber into the glass finishing chamber where it can condense on the 3D printed part. This airflow keeps the air moving inside the finishing chamber, which helps produce a consistent finish on the part. The airflow system is open by necessity but we do not want the exhaust air to become a fume hazard so there is a water bubbler on the exhaust to absorb excess solvent. (Note that this only protects you when using water miscible solvents such as acetone.)
If a spot treatment polish is desired the tube going into the finishing chamber can be disconnected and manually directed onto the part where ever you want. This a great way to apply chemicals for solvent welding (aka gluing parts plastic together).
The other cool thing about this design is that the fog creating components are separate from the fog applying components. This means that you could use a micro controller to do some very precision applications of the fog. As it is, using a simple mechanical timer as shown in the drawing will still give you a ton of control.
Obviously you want to be really careful around solvents. Read the MSDS sheets for any chemicals you use and always wear proper PPE when handling them.
While this machine was designed to allow for use indoors the only solvent I recommend doing this with is acetone. All other solvents should be treated like poison.
Why is acetone special? Actually acetone is some pretty amazing stuff.
Acetone is miscible with water (they mix well), so the bubbler does a decent job of removing it from the air. The absorption of acetone by water is about 1 to 1 by volume, so keep your water fresh to minimize the smell. In any case acetone is perfectly safe for humans under normal circumstances and normal amounts. Believe it or not, the human body actually produces acetone in small amounts!
Acetone is the only commonly available solvent other than water that isn't classified as a VOC or HAP. This means that there are no regulatory restrictions on how much of this solvent we use. No other commonly available solvent is so free of restrictions!
Acetone is the fastest evaporating and one of the strongest of all commonly available solvents and it is very dry (non-oily). So it makes an excellent cleaner and degreaser and this is how it is used in most industries.
Though it doesn’t smell good, you would have to consume a lot of this stuff to be harmed. It is just an irritant in low concentrations, all the bad stuff happens at high concentration levels. Acetone is not regarded as a carcinogen, a mutagenic chemical, or a concern for chronic neurotoxicity effects.
Cool, so what solvents work best for 3D printed plastics?
Acrylic: Most Solvents
PLA: MEK or 'MEK Substitute'
PVC: Most Solvents
Polycarbinate: Pretty solvent resistant
Nylon: Pretty solvent resistant
Polypropylene: Pretty solvent resistant
Polyethylene: Pretty solvent resistant
*Always clean your chambers before switching to a new solvent. This is no joke, mixing chemicals as common as ketones & alcohols can cause an explosion. When in doubt consult a chemical compatibility chart: http://www.safety.vanderbilt.edu/chem/chem-compati...
*Solvents do not "melt" plastic, but rather they dissolve them. Melting means a physical change from solid to liquid caused by an increase in thermal energy. The reaction here is more similar to what happens when you pour water onto a sugar cube.