Analysis of the four main points of three-dimensional printing process control

Three-dimensional printing has been developed on the basis of 3D technology. 3D technology has already appeared since the second industrial revolution, but until 2009, "Avatar" was known as the largest and most technologically advanced 3D ever produced. For movies, 3D technology was officially accepted by people and widely used in various industries.

As a tool for disseminating information, printers use 3D technology for printing to obtain a three-dimensional effect, allowing people to see pictures with vivid images, novel pictures, and strong visual impact, so as to achieve eye-catching or unforgettable. Effect, and this technology is called three-dimensional printing. China's three-dimensional printing technology began in the 1980s, but it has been tepid due to cost and technical constraints. The popularity of the 3D movie "Avatar" has made the printers regain their fighting spirit, and the three-dimensional printing technology is also sailing forward.

The process of three-dimensional printing is very complicated, and its process control points mainly include the following four aspects.

1. Application of grating technology
The application of grating technology can not only eliminate moiré fringes, make the picture smooth and clear, but also improve the clarity, color saturation and three-dimensional sense of the image.

In terms of clarity, without raster processing, the picture around the focus is clearer, the difference between the displacement of the most foreground and the last scene is relatively large, and the entire picture is blurred. To improve the clarity of the picture, the printing accuracy has to be improved, but the printing accuracy After the improvement, the sharpness improvement is not obvious; after the raster processing, no matter the most foreground or the last scene, every part of the picture is very clear, no need to increase the printing accuracy.

In terms of color saturation, the color of the picture is dim and unclear without raster processing, as if it is separated by a layer of white fog. Even with special color management software, the color saturation is still poor; after raster processing, In the case of unchanged materials, the color saturation has been qualitatively improved, the picture is bright and very bright, giving a fresh and bright feeling.

In terms of three-dimensional performance, without raster processing, the three-dimensional sense and clarity cannot be achieved at the same time. The improvement of the three-dimensional sense must be at the cost of reducing the clarity; after the raster processing, not only can ensure the three-dimensional image, but also meet Picture clarity requirements.

Three-dimensional printing should pay special attention to the following points when making gratings.

(1) The number of grating lines. The number of raster lines used for three-dimensional printing is usually higher than 75lpi. For example, the 75lpi raster produced by GOEX is an animated raster, which can produce a clear and stable multi-screen change effect, which can be used for ordinary three-dimensional effects; the raster with a line number of 90lpi is a three-dimensional raster, which can produce a strong sense of depth in the printed matter; The grating with a line number of 159lpi has extremely dense lines and hardly feels the unevenness. It is suitable for anti-counterfeiting packaging.

(2) Grating thickness. Generally, the lower the resolution, the thicker the grating. The thicker grating is suitable for larger three-dimensional posters. Thin raster printing is difficult and suitable for smaller format products.

(3) Grid direction. Normally, the raster is horizontal, suitable for changing picture effect; the raster is vertical, suitable for three-dimensional effect. In the pre-press processing, the direction of the imposition should be determined according to the direction of the grating material, so as to save costs.

(4) Grating size. In general, the larger the grating, the easier it is to deform. The size of common commercial printing grating is 710mm × 510mm. It should be noted that the grating material is not suitable for cutting before printing.

(5) Control of printing environment. Unsuitable temperature and humidity will cause the grating to be deformed. When using it, it should be placed in the printing workshop one day in advance, and the outer packaging should be unpacked. Do not place heavy objects on the packaging to avoid deformation. Re-measure the grating pitch.

2. Image scanning quality
Image scanning quality is directly related to printing quality. When performing image scanning, the characteristics of the original should be analyzed first, and the information such as the tone level, relative contrast, and saturation of the original should be restored as much as possible. Only in this way can the scanning device convert the information on the picture into a complete digital signal . Then the digital signal is processed by image processing software.

3. Screening technology
Three-dimensional printing is the same as ordinary color printing, and the reproduction of the original is also completed by screening. Due to the delicate pixels of the stereoscopic image and the magnifying effect of the lenticular grating, the number of screen lines must be more than 120lpi during plate making; the screen angles of three-dimensional printing and ordinary color printing are different, and the cyan and black versions should use the same screen angle. In addition, for three-dimensional printing with different pitches, the combination angles of the yellow, magenta, cyan and black printing plates should be different to avoid the occurrence of moiré.

4. Field density
Because the three-dimensional printing manuscript consists of closely arranged pixels, and compound gratings are needed after plate making and printing, when selecting the screen angle, in addition to considering the moire formed between the color plates, pay attention to the printing screen Moire formed with grating. Because the 3D three-dimensional printed matter will eventually be compounded with the grating, and most of the gratings have a certain grayscale, and because the number of screen lines used for three-dimensional printing is very fine 300lpi, so only need to be exposed to 8 ~ 90% dots, otherwise it is easy to paste the plate during printing, and it is necessary to increase the amount of ink in the dark area to achieve the effect of 9 ~ 9.5 dots. Therefore, three-dimensional printing has higher solid density than flat four-color offset printing ink.

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