机械工程英语第二版 part2 第11单元翻译

Unit11 Rapid Prototyping and Manufacturing Technologies 快速成型与制造技术Introduction 导言

Manufacturing community is facing two important challenging tasks: Substantial reducition of product development time; and Improvement on flexibility for manufacturing multi-variety and small batch-size products. Computer-aided design and manufacturing(CAD and CAM) have significantly improved the traditional production design and manufacturing. However, there are a number of obstacles in true integration of computer-aided design with computer-aided manufacturing for rapid development of new prodcts.

制造社会面临两个重要的富有挑战性的任务：大幅度减少产品开发时间，提高多种产品，小批量大小产品的制造灵活性。计算机辅助设计与制造(CAD 和CAM)有着显著改善了传统的产品设计及制造。然而，在新产品快速开发方面有一些障碍，这些障碍阻碍着计算机辅助设计与计算机辅助制造的真正集成。

To substantially shorten the time for developing patterns, moulds, and prototypes, some manufacturing enterprise have started to use rapid prototyping(RP) methods for complex partterns making and component prototyping. Over the past few years, a variety of new rapid manufacturing technologies, generally called Rapid Prototyping and Manufacturing(RP & M) have emerged; the technologies developed include stereo lithography(SL),selective laser sintering(SLS), fused deposition modeling(FDM), laminated object manufacturing(LOM), and three dimensional printing(3D Printing). These technologies are capable of directly generating physical objects from CAD databases. They have a common important feature: the prototype part is produced by adding materials rather than removing materials, that is , a part is first modeled by a geometric modeler such as a solid modeler, and then is mathematically sectioned(sliced) into a series of parallel cross-section pieces. For each piece, the curing or binding paths are generated. These curing or binding paths are directly used to instruct the machine for producing the part by solidifying or binding a line of material. After a layer is built, a new layer is built on the previous one in the same way. Thus, the model is built layer by layer from the bottom to top.

为了大大缩短母模，模具和样件的制作时间，一些制造厂开始利用快速原型制造技术(RP)来制作复杂的母模和零

部件的原型。在过去的几年，各种新型的快速制造技术，通常称为快速成型制造(RP&M)已经出现.已开发的技术包括立体光刻(SL), 选择性激光烧结(SLS)，熔融沉积制造(FDM)，分层实体制造(LOM)和三维打印(3D Printing)。这些技术都是直接从CAD数据库生成物体的能力。它们都有一些共同的重要特征：原型件都是通过增材制造，而不是材料去除工艺制作的，也就是说，零件首先通过几何建模软件，如一个零件建模模块来建模，然后用数学的方法进行切层处理，使其成为一连串平行的横截面片，每一平行的横截面片固化的或者具有约束力的路径便生成了。这些固化的或具有约束力的路径就直接用于指导机器通过固化的或者具有约束力的线性层材料生产零部件。每建完一层材料实体，新一层材料实体就会以相同的形式建立在前一层材料实体上。因此，模型是从下到上一层一层建立起来的。

RP Processes 快速成型过程

As mentioned earlier, there are several technologies available for model production based on the principle of "growing" or "additive" manufacturing. The major differences among these technologies are in two aspects: (1) Materials used, and (2) Part building techniques. The following sections will explain in detail these rapid prototyping technologies with respect to the above two aspects.

如前所述，有几种技术的模型制作上载于“成长“或“添加剂“的制造原则为基础。在这些技术的主要区别是在两个方面：(1)所用材料，以及(2)零件创建技术。下面几节将详细说明就上述这些快速原型技术的两个方面。

1.Stereolithography 1.光固化成型机

Stereolithography apparatus (SLA) was invented by Charle Hull of 3D Systems Inc. It is the first commerically available rapid prototyper and is considered as the most widely used prototyping machine. The material used is liquid photo-curable resin. acrylate. Under the initialtion of photons, small molecules(monomers) are polymerized into large molecules. Based on this principle, the part is built in a vat of liquid resin as shown in Fig1.1.

光固化成型机是由3D System公司的Charle Hull发明。它是世界第一台使用最广的商业快速成型机。使用的材料为丙烯酸光敏树脂。在光子的引发下，小分子(单体)聚合成大分子。原型零件就是根据这一原理从树脂槽中制作出来的。如图1.1所示。

The SLA machine creates the prototype by tracing layer cross-section on the surface of the liquid photopolymer pool with a laser beam. Unlike the contouring or zigzag cutter movement used in CNC