Study On Stereolithography Technology And Control Measures Of Prototype Quality

The development of Rapid Prototyping technology has caused the manufacturing industry huge transformation, and this technology has become the multitudinous enterprises and the domestic and foreign well-known university's research hot spot. The stereolithography (SL) technology is the most well-researched,the most mature and the most widespread rapid prototyping technology. This technology has obtained the widespread application in various areas such as design visualization,functional testing,reducing the product updating cycle,enhancing the competitive power concerned the market. Although stereolithography displays more and more advantage in manufacturing, this technology is still developed unceasingly.The principle, application, assortment of SL is introduced in this paper. The three stages of SL, pre-processing, physical fabrication, post-processing, are given. The stereolithography apparatus as well as the property of photosensitive resin is illustrated.The factors that influenced the quality of prototyping are theoretically analyzed and determined in this paper, and the influence of each factor is introduced in detail. The curing process is particularly analyzed, and the theoretical models of curing resin line and layer in stereolithography are determined based on the photosensitive resin SOMOS11120 (E_c=11.5mJ/cm~2, D_P=0.16mm). The theoretical models of curing resin line and layer refer to the curing resin line's maximum depth and width as well as the curing layer's maximum depth. The actual curing layer is coincident with the model comparatively. The research is of theoretical significance to improve SL quality.The warpage of prototype and the elliptic distortion of columned side hole affecting the shape accuracy, the over cure along the build-direction affecting the dimension accuracy, the stair-step effect affecting the surface accuracy are studied experimentally, and success process and quality control measures are proposed: (1) In order to reduce the extent of warpage, the improvement of material proportion, the optimization of process parameters as well as design reasonable supports are effective measures. But the optimal way is reducing the layer thickness reasonably, which can be adjusted by the ratio of the laser power to the scanning velocity. (2) The reduction of CAD model induced error, the Z-compensation method, design reasonable supports are effective measures reducing the elliptic distortion degree of columned side hole. Z-compensation method may effectively reduce the over cure phenomenon which the internal hanging surface of side hole causes, meanwhile this method cannot influence the prototype's other structures except the columned side hole. (3) In the preliminary data processing stage, the Z-compensation to the STL model is the effective action on improving Z-height accuracy. (4) If the surface normal is not perpendicular to the build-direction, the facet will exhibit some stair-step effect. As the angle between the surface normal and the build-direction is smaller, the stair-step effect is more obvious, when the angle between the surface normal and the build-direction is in 0°～30°, the stair-step effect is obvious; When the angle is bigger than 30°, the stair-step effect become inconspicuous, surface accuracy is enhanced. (5) The distance between the scraper and the liquid level has certain influence to the quality of the prototype. The needle-tip and the liquid level should be contacted exactly, and the distance between the scraper and the liquid level should be constant.Finally, the manufacturing process of prototypes with the tiny structures studied experimentally. The success process and quality control measures of the tiny structure are proposed. In view of the influence of Z-compensation to the tiny structure, the "Separating parts—Z-compensation—Sewing parts again" method is applied to the STL model. This method may reduce the influence of Z-compensation to the tiny structure effectively. The primary factor affecting the tiny structure's surface accuracy is the stair-step effect. In order to reduce the influence of the stair-step effect, the building direction of the tiny structure must be adjusted, and the angle between the positioning surface normal and the build-direction must be adjusted within 30°～90°.