5 快速原型及制造.ppt

快速成型制造 12.1 概要 原理：逐层地把合成材料堆叠起来生成原型 优点：可以直接利用零件的几何模型一步地把原型制造出来。整个过程中不需要工序计划，不需要预处理原材料的特种设备，也不需要在几个加工中心中进行移动和传输等 不足：它只能针对某种特定的材料，而NC机床则可以加工绝大多数的工业材料，包括金属 快速原型及制造（Rapid Prototyping and Manufacturing，简称RPM）：快速原型（Rapid Prototyping，简称RP）、分层制造（layer manufacturing）、3维打印（3D printing）、桌面制造（desktop manufacturing），以及实体自由形态制造（solid freeform manufacturing） 基本步骤：首先得到要制造物体的各截面数据，然后逐层地对各个截面进行堆叠，最后把所有的层合并起来。 不需要进行基本特征的设计和特征识别 不需要去定义一个原始坯型 不需要设定各种的装置或复杂的流程去处理材料 不需要考虑装夹、辅助夹紧、定位等工序 不需要对模具进行设计和制造 主要方法： 用激光或者其他光束使相应的树脂聚合 用激光束选择性地使固体微粒或粉末固化 用胶合或熔接的方法粘结液体或固体微粒 切削细薄材料并使其层合 熔化并再固化 Rapid Prototyping Class of technologies that can automatically construct physical models from CAD data. A combination of many thin layers, called slices. Excellent visual aids for communicating ideas. Design testing Faster and less expensive Synonyms: Solid Freeform Fabrication, Computer automated manufacturing, or layered manufacturing. RP vs. Traditional Manufacture (Machining) Rapid Prototyping Process Create a CAD model of the design Solid Modeling Convert the CAD model to STL format Pre-processing Size Location Orientation Auxiliary structure STL File Format The shape of the object is defined by a mesh of tiny triangles laid over the surfaces, like the facets of a cut diamond. It contains the coordinates of the vertices and the direction of the outward normal of each triangle. An approximation of the curved surfaces only. Increase the number of triangles improves the approximation, but at the cost of bigger file size. Sample STL file Auxiliary Structure Why need support? Rapid Prototyping Process Slice the STL file into thin cross-sectional layers 6、Clean and finish the model. Current Techniques and Materials There are more than ten commercial rapid prototyping processes and more than five concept modeling processes; Due to worldwide research, this range is growing quickly. Commercial techniques are available to produce objects from numerous plastics, ceramics, metals, and wood-like p