A brief introduction to the process of stereoscopi

2022-09-19
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Brief introduction to the process of stereoscopic printing rapid prototyping manufacturing

stereoscopic printing molding

this molding method is a rapid prototyping method with the deepest research, the most mature technology and the most widely used in the world at present. In 1984, the stereo printing molding technology was still in the laboratory research stage, and in 1988, the first operable manufacturing system was commercialized. American chryster first applied this technology in engineering practice in 1989, but it did not attract enough attention until 1992. The pioneer of this technology is the American 3D system company, which is the largest and first RP manufacturer in the world. Its product market share is about 30%, and its SLA series products are the best and form a monopoly market

1) process principle

SLA - stereolithography apparatus, also known as stereolithography, light curing, etc. Its basic process principle (as shown in Figure 4) is to carry out the three-dimensional geometric modeling of the required prototype with the help of CAD, generate data files and process them into a faceted model. The inner and outer surfaces of the model are planarized and discretized with small triangles, and the STL (stereolitho - graph) file format, which is widely used in rapid prototyping manufacturing systems and defaults to the industrial standard, is obtained. Cut the model according to the treatment method of equal distance or unequal distance, and form a series of parallel horizontal section slices from the bottom to the top, that is, cut the faceted model into a series of cross sections by computer. The scan line algorithm is used to generate the best path for each section, including the profile path and the internal scan path. At the same time, the model is positioned on the forming system and the supporting structure is designed

slice information and generated path information are used as command files (CLI files) to control the molding machine, and NC instructions at all levels are compiled and sent to the molding machine. The thinner the layer is, the higher the accuracy of the generated parts is. The purpose of using unequal thickness layer is to speed up the forming speed

the laser beam in the laser forming machine is scanned according to the numerical control command, so that the liquid photosensitive resin contained in the container is solidified layer by layer and bonded together. The curing process starts from the first layer of liquid on the working platform. When the first layer is cured, the working platform will fall a certain distance along the z-axis direction (that is, the layer thickness, taking into account the material and process factors), so that a new layer of liquid resin is covered on the cured layer for the second layer of solidification. Repeat this process until the last layer is cured, and a three-dimensional prototype entity is generated. The liquid photosensitive resin contained in the storage tank will solidify in a certain area under the irradiation of a certain wavelength (such as 325nm) and intensity of UV laser, that is, forming a curing point. At the beginning of molding, the working platform is at a certain depth below the liquid level, such as 0.05~0.2mm. The focused laser spot is scanned point by point on the liquid surface according to the instructions of the computer, that is, solidified point by point. When a layer of scanning is completed, the resin that has not been irradiated by the laser is still liquid. Then the lifting frame drives the platform to drop another layer. The newly formed layer is covered with a layer of resin, and then the second layer is scanned to form a new processing layer and firmly connected with the cured part

for the forming machine with laser deflection mirror scanning, the focal length and liquid surface spot size change when the laser beam is deflected, which directly affects the curing of the thin layer. In order to compensate for the changes of focal length and spot size, the scanning speed of laser beam must also be adjusted in real time in the next stage. In addition, when making and providing local supply services for the Asian market for each thin layer, the scanning speed must also be adjusted according to the common high and low temperature test chamber of the processed material, which generally refers to the constant high and low temperature test chamber. Researchers believe that the layer thickness changes (layer thickness changes)

2) system composition

generally, the stereo printing forming system is composed of lasers, X-Y motion devices or laser deflection scanners, photosensitive liquid polymers, polymer containers, control software and lifting worktables

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