3D printing: a guide to post processing

Konstantin Zhelty — specialist in 3D printing from PrintProduct company

Post-processing is one of the most important stages of 3D printing. It can help you to get rid of both the print nuances (waviness and other defects) and the gluing traces. Another benefit of post-processing is strengthening of a finished 3D model. Thus, post-processing adds beauty to the finished model and additionally makes it strong.

Post-processing objectives

Post-processing is designed to:

• protect a finished product from the environment;
• hide the shortcomings of FDM technology;
• to finalize a model look;
• paint the model in the desired color;

Post-processing types

1. With the use of chemicals:

• solvents;
• special bath;
• additional coverage.

2. With the help of physical effects:

• sandpaper;
• grinding;
• other tools (engraver, scalpel, etc.)

Let’s take a closer look at the chemical post-processing. As we mentioned, there are several ways to perform it:

1. Solvents and their kinds:

• dichloromethane, dichloroethane (this one reacts not so well) are used for gluing;
• solvent is also used as a glue;
• acetone is used for the treatment of ABS plastic;
• formic acid is necessary for gluing toghether polyamide, nylon or caprolon 6, as you prefer.

You can also use other solvents when appropriate.

2. Special “bath”

In our opinion, acetone bath is the perfect thing for post-processing. So why is it useful?

• It is completely sealed.
• It’s effect is based on the use of tubular electric heaters, which heat the solvent and spay the steam on all sides. This helps to save the material and process the part perfectly, without any extra smudges.
• There are several sizes of “bath” and the second floor inside it, so you can print a few small items, place them together and process at a time.
• Average processing time is about an hour.
• Acetone is used as a solvent. Generally one can use any solvent other than dichloromethane, and we do not recommend using benzene and formic acid (it may cause poisoning if the “bath” happens to be open during the operation).

3. Additional coverage

This is coating that can protect PLA plastic from the environment. In our case filler “1 + 1” is used. Two components are mixed in a certain proportion, diluted together in a container and applied in several layers. It helps to give a transparent form and good adhesion of paint to the the last layer of the element, so it will not break away. This is especially important for those models that will constantly work outside, because “1 + 1” compound doesn’t soften under the sun, environment doesn’t affect the material in any way.

Post-processing main stages

• Gluing. To stick the details together you can use either dichloromethane or dichloroethane. Specific kinds of dichloromethane (preferably clean) can be better applicable for various plastics.
• Cleaning. Remove coarse, undesirable elements (with sandpaper, engraver, etc.)
• Additional compound. For example, the composition of the “1 + 1” fills all irregularities, his task is to align the entire layer and give smoothness to the top layer to further apply primer filler. Before you apply primer filler, it is necessary to apply several layers of “1 + 1” processed before each layer with sandpaper. This is to ensure that the subsequent layer is fastened to the previous.
• Filler. It is needed as a link between the composition of “1 + 1” and paint, so it does not break off or drop off under mechanical force influence — primer filler absorbs it.
• Paint and varnish. Use sandpaper once again and then apply paint and varnish. After that “1 + 1” compound can be applied again to protect the paint itself.

Post-processing examples

1. Mask “The Last Airbender”

• Material: SHERLOCK
• Adhesive: Solvent
• Second layer: “1 + 1” compound
• Third layer: primer filler
• The last layer: painting + varnish. In this case, the varnish consists of two elements: protective layer of varnish was applied first, and a varnish with an additional phosphor was applied second to all the white elements on the mask.

2. Mask «Tes Skyrim»

• Material: PLA
• Adhesive: dichloromethane
• Second layer: the composition of “1 + 1”
• Third layer: primer filler
• The last layer: paint + varnish.

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Check out previous materials on the topic:

• Recent developments in 3D printing. Material selection