The process of 3D stereolithography is very complex, and the key points of the process control mainly include the following four aspects.
1. application of grating technology
The application of grating technology can not only eliminate moire fringe, make the picture smooth and clear in layers, but also improve the clarity, color saturation and stereoscopic sense of the image.
In terms of clarity, without grating processing, the picture around the focus is clear, the displacement difference between the most foreground and the last scene is relatively large, and the whole picture is relatively fuzzy. In order to improve the clarity of the picture, it is necessary to raise the definition of the picture High printing accuracy, but after the printing accuracy is improved, the clarity is not obvious; after the grating processing, no matter the most foreground and the final scene, every part of the screen is very clear, and no additional improvement of printing accuracy is required.
In terms of color saturation, the color of the screen is relatively dim and blurred without grating processing, which is like a layer of white fog. Even if special color management software is adopted, the color saturation is still poor; after the grating treatment, the color saturation has been improved in quality under the condition of the material unchanged. The color saturation of the screen is bright and very bright, which gives a fresh and bright feeling Sleep.
In the performance of stereoscopic sense, without grating processing, stereo sense and clarity can not be obtained simultaneously. To improve the stereoscopic sense must be at the cost of reducing the clarity; after the grating processing, it can not only guarantee the stereoscopic sense of the picture, but also meet the requirements of the picture clarity.
The following points should be paid special attention to when making grating in 3D stereo printing.
(1) Number of raster lines. The number of grating lines used in stereolithography is usually higher than 75lpi. For example, the 75lpi grating produced by goex company is an animation grating, which can produce clear and stable multi picture change effect, which can be used for general stereoscopic effect; the grating with 90lpi grating is a stereo grating, which can make the printing products produce strong longitudinal feeling; the grating with 159lpi grating has very dense lines, and it can hardly feel bump and bump, so it is suitable for anti-counterfeiting packaging.
(2) Grating thickness. The lower the general resolution, the thicker the grating, the thicker the grating is suitable for the larger 3D poster. The thinner grating printing is difficult and suitable for small format products.
(3) Grid direction. Generally, the grating is horizontal, which is suitable for changing the picture effect; the grating is vertical and suitable for the stereoscopic effect. In the pre printing process, the direction of the plate assembly should be determined according to the direction of the grating material, so as to save the cost.
(4) Grating size. Generally, the larger the grating, the easier it will be to deform. The common grating size for commercial printing is 710mm × 510mm. It is important to note that grating materials are not suitable for cutting before printing.
(5) Control of printing environment. Improper temperature and humidity will cause grating deformation. When using, it should be placed in the printing workshop one day in advance, and the outer packaging should be disassembled. Do not put heavy objects on the package to avoid deformation. For the grating which has been placed for a long time, the grating spacing must be measured again before printing.
2. image scanning quality
The quality of image scanning is directly related to the printing quality. In image scanning, the characteristics of the original should be analyzed first, and the information of the order level, relative contrast and saturation of the original should be restored as much as possible. Only in this way can the scanning equipment convert the information on the picture into a complete digital signal. Then, the digital signal is processed by image processing software.
3. network adding technology
As with the ordinary color printing, 3D printing is also used to reproduce the original by adding net. Due to the fine pixel of stereoscopic image, plus the amplification of column mirror grating, the number of net lines must be more than 120lpi when making plate; the mesh adding angle of 3D stereoprinting and common color printing is different, and the blue and black plates should adopt the same mesh adding angle, and the three-dimensional printing with different grid spacing, yellow, magenta, green and black four printing plates The angle of the combination of the mesh lines should be different to avoid the moire fringe.
4. field density
Since the original 3D printing is composed of a closely arranged pixel, and the grating is also composite after plate making and printing, when selecting the angle of the mesh line, the moire formed between different colors of the plates should be considered, and the moire formed by the screen and grating should be paid attention to. Because 3D stereoscopic printing products are finally combined with grating, and most of the grating pieces have certain gray level. Because the number of screen lines used in 3D printing is very fine 300lpi, only 8-9% dot is needed in the printing process, otherwise it is easy to paste the plate, and thus the ink quantity in the dark adjustment area should be increased to achieve the effect of 9-9.5% dot. So 3D printing is higher than that of flat four color offset printing ink.
