3D printing is great. With one machine, you can create nearly any shape to satisfy your rapid prototyping needs. But sometimes, you dont want a prototype. You want a nice, strong, high quality final product. With just a little post print work with Acetone on your ABS prints, you can have it.

Acetone finishing greatly increases the strength of your prints. The smoothing process helps to bond the layers together, which helps prevent delamination. It also helps smooth out any weird printing artifacts, and gives your prints a nice, swanky shine.

Step 1: Equipment and Materials

Some stuff you'll be needing

Kettle Steamer: This serves as your vapor chamber. I got the "Presto 06006 Kitchen Kettle Multi-Cooker/Steamer", available on walmart and amazon
Acetone: You can get it from any hardware store.
File/Sandpaper: You will be doing only light, targeted work, so a file is better. I just used my leatherman.
Glass Applicator Bottles: These guys help applying acetone and acetone/ABS slurry to the right spots. I have one for every color filament i use, plus one with pure acetone. I got a six pack of these guys, but you can also use old nail polish remover bottles.
ABS Print: For this example, i used this ocarina from thingiverse. Note that this method doesn't work on PLA.

Step 2: Vapor Bath

Once you've finished printing it's time to start finishing. First check your prints for any obvious defects. The vapor bath will smooth out the layers, but any large bubble or strings can cause problems. Give them a quick filing or cut them off with a razor blade. You dont need to go overboard here, the vapor bath will do most of the work.

Next, Warm up your steamer-turned-vapor-bath in a well ventilated area. Acetone already has a pretty low boiling point (around 135° F), so you dont need to crank it up too high (i just set mine to "warm"). Its important to note that acetone vapour is flammable, and none too pleasant to inhale. Make sure you set up away from open flame, and have good airflow. I make sure mines near an open window, and have a fan to blow the exhaust out.

Arrange your pieces in the steamer tray. Avoid having pieces touch each other, and minimize the contact with the basket. Place the basket into your heated steamer pot. Now, add your acetone. Depending on the shape and complexity of your print, you can do this one of two different ways:.

The best way is to splash small amounts of acetone evenly over the prints. The run off should pool at the bottom and boil off into vapor, to help catch the places the splashing missed. You can supplement this by adding some more acetone directly to the bottom of the pot. Let it stew in the vapor for about 30 seconds.

This is quick and gets good, even results with less acetone. however it can be dangerous to the print. If you pour too much acetone directly on the print, or if the prints are too thing, or if they have cavities where the acetone can pool, you can destroy your print. In this cases use the "safe" way.

The safest way is to first boil off a modest amount of acetone into the steamer, then place the basket in and put the lid on. Let it stew for a few minutes. Keep an eye on it, and you can see the vapor smooth the layers, which will give you an idea of when its done. If you have a particularly large part, you will want to rotate it and dip it again. Use a pencil or stick to help you grab and rotate it. If you touch the surface you can leave fingerprints.

The main this to worry about is that your vapor layer is deep enough encompass the whole print. You can get a sense of how much vapor there is by putting your and into the middle of the pot (without touching anything, naturally). You will feel a cooling on your fingers where the acetone collects and then evaporates. Add more acetone to the bottom if necessary.

Once your done, take the basket out and let it dry.

Step 3: Cleanup

Once removed from the bath, your prints will be very sticky to the touch. Avoid touching it too much since you will leave marks and scuffs, which you'll have to remove later. After about 3-5 minutes the print will no longer be sticky, and you can pick it up. However the surface will still be soft and spongy, and you will need 30-60 minutes for it to harden enough to be filed and sanded.

Once dry, you can do another round of filing. Take care of any uneven places that arose from the vapor bath. Usually the area that contacts the basket needs filing, plus any fingerprints you may have left.

Now we can use our acetone slurry to combine parts, fill in any holes or or grooves, and smooth any areas the vapor bath might have missed. Acetone slurry is made by simply letting ABS dissolve into some acetone. I just use scrap from failed prints and support structures. You should aim to get it nice and thick, with probably about 30% ABS scraps to acetone by volume (though a lot depends on the quality of the filament)

Apply the slurry generously. Having some excess is ok, as we will do a final round of filing in the end. Like before, give it some time to properly harden.

Step 4: Post Processing

Once everything has hardened back up again, we can do our final cleanup. Slurries made from some colored filaments can leave behind a white film behind when they dry. The easiest way to get rid of this is just brush on a little pure acetone.

Use the file to smooth off any excess plastic from the previous step. Use pure acetone to touch up the sanded areas. If necessary, repeat the slurry/sanding/touchup process, otherwise you are done!