Acetone Vapor Polishing for 3D Printed ABS Plastic

Acetone Vapor Polishing is a process for smoothing over untreated 3D printed ABS plastic parts. By exposing the print to acetone vapors the individual print layers fuse together leaving behind a glossy surface. This treatment is particularly good for prepping a piece for another process such as painting but it can also be used as a finished surface.

Tips

This will only work on ABS plastic, not PLA prints. If you are unsure of the type of material check with where you had your piece printed

This process is not recommended if your piece needs to maintain specific measurements - The vapor rounds over print features and there is a small amount of shrinkage that takes place.

Use only pure acetone- Do not try this with nail polish remover (will not be as effective, and there are too many other chemicals you will be vaporizing)

Only do this in a ventilated area

Wear normal safety gear: goggles, nitrile gloves, and respirator

NEVER leave acetone on the burner unattended- it is flammable!

Step 1: Prep Your Surfaces

Start with a clean and dry ABS print.

Using files solely dedicated to plastic cleanup (flat and/or half round) spend some time filing your print's surface especially if it is a course resolution print (such as from a Stratasys Dimension). It is important that your files weren't used for other things- wood or metal particles can fuse into your print during this process, making for a bad finish.

This filing does not need to be overly time-consuming and you don't have to go over the whole piece; the vapor will fuse much of the print layers together, but filing ensures a smoother surface because it breaks the more aggressive points and layers on your print that acetone can't get rid of. Without doing this, your print may look wavy in some parts at the end.

Step 2: Secure Your Piece

To expose the piece to the vapor you will need to suspend your piece above the acetone.

You must find a way to hang your piece- Exposing the piece to vapor with just your hand is not a good or safe option for vaporizing- the surface of the print will become sticky and you will be ruining your smooth surface you are trying to achieve and you will be exposing yourself to the vapor. Work safely!

Steel binding wire makes for a good hanger. With a piece about 12" long, use clippers to notch one end.
Find a place on your piece that is inconspicuous to insert a wire. This is a place that depending on your piece might be covered with something else afterward. If you are planning to paint your piece afterward this hole can be patched with a small amount of body filler and sanded.
Use a torch to heat the notched end.
When the end is red hot, stick it into the area into the chosen area and push it in about a quarter inch
Hold it in place for around 30 seconds, or until the plastic hardens again - Try to keep the wire still for the best connection.
Once cooled the piece should be secure and stationary on its new hanger, and ready to be smoothed

Step 3: Set Up Your Acetone

With your part prepped you need to prep your acetone setup next:

In a well ventilated area, place a Pyrex beaker with a lid (or any lidded container, I prefer a beaker so I can see the boil) onto a hot plate.
Your beaker should be larger enough that your piece can fit and move within it.
Fill the container with about a half an inch of acetone, and turn on the hot plate to a medium heat with the cover on. Always fill the container first before turning on the heat.
The liquid is ready when there are some bubbles (a low simmer) - Your acetone should never be at a rolling boil.

Tips

Use only pure acetone- Do not try this with nail polish remover (will not be as effective, and there are too many other chemicals you will be vaporizing)
Do not leave this setup unattended! Acetone is flammable.

Step 4: Vapor Polishing

When your acetone is at a mild boil/ slow simmer you can expose the piece to the vapors:

Holding the hanger, suspend your piece above the liquid, while keeping the container as covered as possible
Check the piece's progress and turning it regularly, the smoothing will be fairly instantaneous but it needs to be rotated for even exposure.
Do Not Touch the surface of the piece.
Keep exposing the piece and taking it out to inspect it.
It is done when the surfaces are consistent and you are happy with the outcome.

Tip

A piece can become over exposed- when you begin to see small pinholes, this is a good sign to stop, as more holes will surface. At this point, the layers are fused and are starting to expose the hollow interiors of your piece.

Step 5: Hang to Dry

After taking the piece out of the vapor, and you are happy with the look of the piece, it is important not to touch it. The piece will be sticky for a few minutes so hang it somewhere out of the way where it can harden again.

This takes around 5 minutes, but I like to wait around 10 minutes while I clean up the work area.

Tip

Any leftover acetone may be put back in its original container, but it must cool down first. DO NOT put hot acetone back into its container or dump it down the drain.

Step 6: Finishing

After hardening, inspect your piece. It should have a consistent glossy finish. If are happy with the outcome, you can pull or twist your piece off the wire hanger. (if you are planning on painting the piece you can choose to leave the hanger in- it will work well for holding and suspending during the process)

Finishing

If it all looks good you can keep it the way it is, or sand the piece for a finer matte finish.
If you find that there are still surface inconsistencies, you can file or sand them away and smooth it over again
If you are planning on painting your piece now you can move on to priming and painting

Holes

The hole from the hanger should be a pretty minimal in appearance and should easy to clean up. As stated before it should have been placed in an area that will later be covered or not as noticeable. If you are painting the piece, the hole can be filled with a bit of spot filler and sanded before painting.