先进制造技术 第十单元

10 Rapid Prototyping and Manufacturing

10.1 Introduction

10.1.1 What Is RP&M

Manufacturing community is facing two important challenging tasks:

(1) Substantial reduction of product development time; and (2) improvement on the flexibility for manufacturing small batch and diversified products. Computer-aided design and manufacturing (CAD and CAM) have significantly improved the traditional product 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 products. Although substantial research has been done in the past for computer-aided design and manufacturing integration, such as feature recognition, CNC programming and process planning, the gap between CAD and CAM remains unfilled in the following aspects:

(1) Rapid creation of 3D models and prototypes.

(2) Cost-effective production of patterns and moulds with complex surfaces.

To substantially shorten the time for developing patterns, moulds, and prototypes, some manufacturing enterprises have started to use rapid prototyping (RP) methods for complex patterns 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 Stereolithography (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.

10.1.2 The History of RP&M

As usual with invention, one individual's impatience was the propellant for the rapid prototyping industry, now barely two decades old. Its father, Charles

W Hull, founded 3D Systems of Valencia, Calif. in 1986. As an engineer, Hull had always been bothered by the long time it took to make prototype models of plastic. They had to be machined by hand, he recalls. If more than one was needed, generally the case in industry, molds for making plastic prototypes had to be individually machined.

Hull had been working for a small company that used ultraviolet lamps to