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21st Century Manufacturing Episode 1 Part 8

Tham khảo tài liệu '21st century manufacturing episode 1 part 8', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 134 Solid Freeform Fabrication SFF and Rapid Prototyping Chap. 4 Figure 4.2 Stereolithography SLA based on the commercially published brochures of 3D Systems Inc. The helium-cadmium laser in the SLA-250 cures and fuses successive layers of resin. These descend on top of each other on the elevator until the whole part is formed at which point the object is lifted from the vat. TABLE 4.1 History of SLA Date Person s Company and location Activity 1970s A. Herbert 3M. Minneapolis R D 1970s H. Kodama Nagoya Prefecture Research Japan R D 1970s C.Hull Ultra Violet Products California R .D 1986 c. Hull 3D Systems Inc. formed from Patent secured and R. Freed Ultra Violet Products California November 3D Systems 3D Systems Demonstration of the 1987 SLA-1 which became the SLA-250 at the Autofact show in Detroit leg forming a solid shape. Then the use of a helium-cadmium laser created more energy and more focused solidification patterns than a simple uv arc lamp. Finally the rapidly decreasing costs of microprocessors during the early 1980s paved the way for the tessellation routines during CAD and the control of the lasers in the actual SLA machine. 4.2 Stereolithography A General Overview 135 One can also imagine the excitement these first inventors felt as they saw the first layer of SLA material solidifying on the surface of a vat of resin viewed at an angle it resembles the first layers of ice solidifying on a pond in early winter. In production once this first layer is cured the elevator type stage lowers by 50 to 200 microns 0.002 to 0.008 inch depending on the desired accuracy and further layers are cured and connected by self-fusing to the previous ones. At the end of the process the elevator rises and the component is Itfted out and cured in its entirety. Postcuring is needed probably overnight before the prototype is ready for use. Hand sanding may be requừed to mitigate the stair-stepping effect described later. Note that the object in Figure 4.2 has overhanging .