Knowledge of 3D printing materials
In order to ensure the three-dimensional effect of three-dimensional printing, when considering the material of the grating, it is also necessary to select the grating with different parameters in combination with the image effect. 1. The material of the grating The material of the grating should have high transparency, high refractive index, good gloss, strong plasticity, stability and other properties. The materials used for making toys and Food Packaging also require non-toxic and harmless. At present, three kinds of grating plates made of polystyrene (PET), polypropylene (PP) and polyvinyl chloride (PVC) are mainly used in the market. ①Polystyrene resin (PET) Polystyrene (PET) is used to make hard plastic gratings and can be printed directly with ordinary ink. The polystyrene raw material is processed by injection molding to form a concave-convex cylindrical mirror grating. Polystyrene is colorless and transparent (transparency is 88% -92%), refractive index is 1.59-1.6, non-ductile and flammable. Because of such a high refractive index, it has good gloss. Its tensile strength is 3.52-6.33MPa, its bending strength is 6.12-9.84MPa, and its thermal deformation temperature is 70-98 ° C. The chemical properties of polystyrene are resistant to certain mineral oils, organic acids, alkalis, salts, lower alcohols and their aqueous solutions. It is softened after being eroded by hydrocarbons, ketones, higher fatty esters, etc. It is soluble in aromatic hydrocarbons and toluene, ethylbenzene and styrene monomers. In some cases, the degree of erosion of polystyrene by chemical reagents can be reduced by annealing, stress relief and other measures. Polystyrene has good stability, high picture quality, non-toxic raw materials, and high chemical resistance, but it is more difficult to bond and process. Mostly used in toys, fine advertising, etc. ② Polypropylene (PP) Polypropylene (PP) can be printed directly with ordinary ink, but the surface should be treated with sparks, and the ink dries faster than polystyrene. Polypropylene is softer than polystyrene and harder than polyvinyl chloride. The stability is high, but the image quality is average. The raw materials are non-toxic, low chemical resistance, easy to bond processing, mostly used in packaging, stationery, etc. ③ Polyvinyl chloride (PVC) Polyvinyl chloride (PVC) is used to make soft plastic cylindrical lens grating. A hot oil press is required to press and shape the picture and the PVC film base through a metal grating drum or grating plate. Polyvinyl chloride is a polymer compound formed by polymerizing chlorinated olefins and is difficult to burn. Although polyvinyl chloride and polyethylene are both milky white, polyvinyl chloride can be made into a colorless, transparent and shiny film, and can produce various softness films according to the content of plasticizer. The fastness of this material after pulse heat sealing and high frequency heat sealing is also large. The chemical properties of PVC have good chemical resistance, but poor thermal stability and light resistance. Hydrogen chloride begins to decompose at 140 ° C, and stabilizers need to be added during manufacturing. Polyvinyl chloride has a chlorine content of 56% -58%. Low molecular weight is easily soluble in ketones, esters and chlorinated hydrocarbon solvents; high molecular weight is difficult to dissolve. Polyvinyl chloride has low stability and rough picture quality. In addition, because the PVC grating is toxic and not environmentally friendly, it is generally not used in toys and food packaging products in European and American countries. According to the principle of stereo vision, if we can allow our left and right eyes to see two images taken at different positions, the brain can synthesize the two images and feel a three-dimensional space. Different images can be seen from different angles by using the split-image effect of the grating plate, so if we place the grating perpendicular to the two eyes, the two eyes will see two different angles due to the different viewing angles of the grating on the two eyes The image, resulting in a three-dimensional sense. In order to obtain a better stereoscopic effect, it is usually not made with two images, but with a sequence of stereoscopic images to construct. In such a case, according to the different observation positions, as long as you see two pairs in this sequence at the same time Image, you can feel the three-dimensional effect. Stereo gratings require delicate images and sharp changes, so the viewing angle range is smaller, so that the visual effect is real and the stereoscopic effect is strong. The variable grating places the grating flat between the two eyes. Note that the line angles of the two eyes to the grating must be parallel, so the two eyes see the same image. If the image is composed of a series of continuous animations, then when the eyes are up and down When you move or flip the grating up and down, the angle between the eyes and the grating will change, and we will also see successive images one after another, that is, see the effect of a change. The variable grating requires a larger viewing angle range, so that the image conversion range is larger, and there is less crossover between different images, and the image conversion can be clearly felt. According to the analysis, it can be known that this type of grating requires a smaller ratio of thickness to pitch, so that a larger viewing angle range can be obtained. If the stereoscopic grating is used to produce the aberration effect, it often leads to incomplete extinction; while the stereoscopic grating is used to produce the stereoscopic effect, the stereoscopic effect will not be strong. Therefore, the appropriate grating plate should be selected according to the desired performance. 3. Method for precise measurement of grating pitch The grating pitch is generally matched precisely by using a series of grating test strips with a nominal pitch. There are many types of grating pitch test strips. Different software vendors use different test strips, but the basic principles are basically similar. It is to use the split-image characteristics of the grating plate and load different grating pitch parameters to create a series of black and white patterns, so that when the grating plate is in accordance with the nominal grating pitch, it will show a specific angle when viewed at a certain angle. pattern. It is composed of a series of black and white stripes. When testing, a grating is pressed on the grating test strip. When one of them can be seen at a certain angle, it will show a completely white pattern. When a completely black pattern is present, the grid pitch value under the test strip is the actual grid pitch of the grating plate.
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2. Choose the grating material according to the final effect of the picture