The working principle of 3D printing is through layer-by-layer overlay molding, then there will be a step effect in layered manufacturing. Although each layer is very thin, but under the micro size, there will still be multi-level steps with a certain thickness. 3Dprinting surface quality is related to the printing materials, machine accuracy, printing speed, temperature, 3D modeling data quality, and slice parameters. In order to achieve nice appearance finishing, we engineers work hard on the post-processing of the model. Now let me introduces several common post-processing processes!
- Sandpaper grinding
The surface of 3D printed items sometimes is rough and needs polishing. Polishing is divided into physical polishing and chemical polishing. Although FDM technology equipment can produce high-quality parts, it has to be said that the layers of layers on the parts are visible to the naked eye, especially when there is a large amount of support, which often affects the user’s judgment, especially when appearance is an important evaluating factor, sandpaper polishing is quite necessary.
Sandpaper grinding principle: coarse first, then fine, rough first and then fine.
- Chemical polishing
Take ABS material an example. It can be polished with acetone vapor, or boiled in a ventilated place to fume the printed parts, or choose other polishing machines on the market;
However, PLA materials cannot be polished with acetone. There are special PLA polishing oils, but chemical polishing for PLA need careful handling. As you have to bear corrosion on the surface. Generally, chemical polishing is not yet mature enough, and it is not widely used, it can be one of the alternatives for post-processing.
Sand blasting on the surface of the concrete is also a common post-treatment process. The operator holds the nozzle to spray the medium beads at high speed towards the polishing object to achieve the polishing effect. Pearlescent treatment is generally faster, and can be completed in about 5-10 minutes. After treatment, the product surface is smooth and has a uniform matte effect. The following is a comparison chart:
- Surface coloring
Except for products printed by full-color 3D printing equipment, other 3D printing equipment generally can only print a single color. Sometimes it is necessary to color the printed objects, such as ABS plastic, photosensitive resin, nylon, metal, etc. Different materials need different pigments.
General process of coloring:(there is also another article about coloring process)
1) Background color
Use a spray gun to select a primer that is close to the color of the finished product. Generally, thin coating is used, and layers are superimposed. The details and the part with a large contrast can be reserved without spraying.
2) Color block coloring
Generally, the coloring should follow the process from large area to large area, from spraying to hand coating. This will help improve efficiency. First, spray the large-area color blocks, then hand-paint the small-area color blocks, spray and add the hand-paint to complete the overall color drawing.
3) Color adjustment
The spray polishing stage, this step is mainly through layer-by-layer overlay, overlay, overprint, gradient, transition and other color adjustments to emphasize the color structure and details.
4) Coloring local details
Mainly describes the details, such as the motif of the characters, details of clothing, distressing, imitation copper, etc. By depicting the details, the original image of the model is highly restored, the modeling features are highlighted, and the most realistic model is created.
5) Light sensor adjustment
Fine color adjustment for light perception adjustment is mainly divided into two categories: matte processing and glossy processing. According to customer needs, use matte oil or varnish to adjust the texture to create overall matte or light, and partially matte or light to achieve a highly simulated model texture.