Vapor treating: How to smooth PLA or ABS prints

Vapor treating is a way of smoothening the surface of a print with a fluid that can dissolve the material of the print. This is done by vaporizing the fluid in a "vapor jar", which is nothing more than a jar that can hold the vapor. For ABS acetone is used as a fluid and you can use chloroform for PLA.

By heating the fluid a vapor with little drops of the solvent will be formed. This will slowly settle on the print and start to dissolve the outer layer. When timed correctly you are able to get a very smoothly finished print, similar to an injection molded part.

The advantage of using a vapor jar as compared to just dipping the print in the solvent is that the solvent is equally distributed over the print. This will give a more consistent result.

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The goal: a smooth finished print as the Ultimaker robot on the left

Safety precautions

Using fluids such as acetone and chloroform is at your own risk; make sure to only use it if you know how to work with these materials!

Before you start there are a couple of things to keep in mind:

  • Printing with ABS produces fumes and releases UFPD’s (Ultra Fine Particles), so make sure to print in a well-ventilated area. When inhaled they can cause inflammation to the respiratory system, headache or nausea.
  • Acetone vapors can cause irritation or muscle weakness and are highly flammable, so keep it away from fire.
  • The vapors released by chloroform can be irritating to the eyes/skin or respiratory tract. They may also cause dizziness.
  • Always dispose the leftover solvents in a chemical box.

What do you need?

  • Your Ultimaker, preferably with heated bed
  • Prints (ABS and/or PLA)
  • A glass jar or container that fits in your Ultimaker
  • A solvent (high concentration acetone for ABS, chloroform for PLA)
  • Aluminum foil and/or cling film
  • Something to lift your print out of the jar
  • Spare hot end fan (e.g. Sunon mc25060V1 0004-A99)

Note: If you don't have an Ultimaker with heated bed you can use a cooking plate instead.

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Necessities for vapor treating

Printing tips

For the best results there are a few things to keep in mind when selecting a print. First of all it's recommended to not use a model with too fine details, as the vapor may dissolve the details. For this reason you can also use a print with thicker layer height (e.g. 0.3 mm). Secondly, make sure that the model is not too tall. Because the vapor is heavy the bottom of the print will stay in the vapor longer, thus giving it more time to dissolve the material. If the model would be too tall it might lead to unequal distribution of the vapor on the print.

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An ABS print with a layer height of 0.3 mm

Preparing the vapor jar

When you have collected everything that you need, you can start creating the vapor jar. Please keep in mind that the vapor jar needs to be placed in a room where you can ventilate properly.

  1. Move the print head towards the back left corner and place the glass jar on the build plate.
  2. Heat up the build plate to 110 degrees and wait for approximately 15 minutes so that the glass jar becomes warm too. Depending on the thickness of the glass the waiting time can be a little bit different.
  3. Unplug the hot end fan from the connecter on top of the print head and attach the spare fan to the connector.
  4. Place the fan halfway into the jar, so it doesn't touch the bottom of the jar and cover the wires of the fan (e.g. with some tape) to protect it against the vapor.

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The setup

The vapor treating process

After the vapor jar has been made, you're ready to start the vapor treating process. Therefore, simply take the following steps.

  1. Start by pouring approximately 50 ml of the solvent into the jar.
  2. Put the print on a piece of aluminum foil on the tool you use to hold the print and place it in the jar. In this example we used a skimmer to hold the print.
  3. Cover the jar with cling film and/or aluminum foil.
  4. Give the solvent a minute to vaporize.
  5. After a minute you can connect the fan so the vapor is distributed over the print.
  6. Leave the print in for 5-10 minutes or until you are satisfied with the result. You will see that the print slowly starts to become smooth.

Once finished your prints will look like this:

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