With the continuous development of 3D printing technology, more and more users begin to apply 3D printing in many fields, such as model making, product prototype development, educational display and personal creative design. However, although 3D printers can realize complex geometric structures, the finished products printed by them are often rough in appearance and single in color, which cannot meet the aesthetic or exhibition needs. Therefore, painting and coloring 3D printed parts has become an important step to improve the visual effect of finished products. This paper will introduce in detail the process and skills of painting and coloring 3D printed parts.

I. Preparations

Before painting and coloring, 3D printed parts need to be properly treated first. Common 3D printing materials such as PLA, ABS, PETG, etc., although the materials are different, the basic surface treatment steps are similar:

1. Remove the supporting structure: Use scissors or tweezers to carefully remove the supporting materials generated in the printing process to avoid damaging the model surface.

2. Polishing treatment: Use sandpaper (from coarse to fine, such as 200 mesh →400 mesh →600 mesh →1000 mesh) to polish the model surface step by step, so as to remove layering and burrs and make the surface smoother.

3. Clean the surface: clean the model surface with alcohol or soapy water, remove dust and grease, and ensure that the paint adheres firmly.

Second, the primer spraying

The function of primer is to enhance the adhesion of topcoat and improve the durability and aesthetics of the whole coating. It is recommended to use gray or white primer, and attention should be paid to:

-keep the distance between the spray gun and the model surface about 20-30 cm;

-spraying should be uniform, and layered spraying is better;
　　-After spraying, each layer should wait for sufficient drying (usually 30 minutes to 1 hour) before proceeding to the next layer.

After the primer is sprayed, it can be slightly polished again to further improve the surface finish.

Third, paint spraying
　　The topcoat determines the final color effect, and can be painted in monochrome or multicolor according to the design requirements. The following principles should be followed when painting:

-Use high-quality painting products, such as car painting or professional model painting;

-Follow the principle of "thin layer and multi-spraying" to avoid dripping or foaming;

-Shake the tank well before painting to ensure the uniform distribution of pigments;

-If multi-color spraying is needed, cover tape can be used for partition protection and color layer by layer.

In addition, for the details, the brush can be used for local complementary color to enhance the three-dimensional sense and realism of the model.

IV. Surface Protection and Post-treatment

In order to improve the durability and gloss of the finished product, it is suggested to spray varnish for protection after the topcoat is dried. Varnish has a variety of options, such as bright, semi-light and matte, which can be matched according to demand.

Finally, polishing tools can be used to polish the model or polishing paste can be used to polish the surface to make the model more textured.

V. Matters needing attention

-Wear a mask and gloves when operating, and conduct it in a well-ventilated environment;

-Avoid spraying in high temperature or humid environment, so as not to affect the coating adhesion;

-Different materials have different adaptability to paint, so it is recommended to conduct a small sample test first.

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By painting and coloring 3D printed parts, not only the visual effect can be improved, but also the detail expression and artistic value of the model can be enhanced. Mastering the correct painting process is one of the important skills for every 3D printing enthusiast and professional to improve the quality of his works. I hope this article can provide practical reference for readers and help create more exquisite and professional 3D works.