It integrates processing knowledge into the design of a part to obtain maximum benefits and capabilities of the manufacturing method.. To come up with the best design, the manufacturing
Trang 1a tool that guides the designer in coming up with better design choices and then provides the optimum design It is a tool for concept generation, concept approval, and concept improvement It integrates processing knowledge into the design of a part to obtain maximum benefits and capabilities of the manufacturing method To come up with the best design, the manufacturing engineer should have a good knowledge of the benefits and limitations of various composite manufacturing techniques The team members should also
be familiar with tools such as design for manufacturing (DFM), design for assembly (DFA), etc for developing high-quality design As compared to metals, composite materials offer the highest potential of utilizing DFM and part integration, and therefore can significantly reduce the cost of production Engineers utilizing isotropic materials such as aluminum and steel tradi-tionally fabricate parts by first selecting raw materials from a design hand-book based on performance requirements Once the raw material is selected, the manufacturing process to fabricate the part is identified This philosophy
is not viable in the field of composite materials With engineered composite materials, the material selection, design, and manufacturing processes all merge into a continuum philosophy embodying both design and manufac-ture in an integrated fashion For example, a rod produced by filament winding, pultrusion, RTM, or braiding would impart distinct stiffness, damping, and mass characteristics due to different fiber and resin distribu-tions and fiber volume fracdistribu-tions Composites manufacturing processes create distinct microstructural properties in the product
The best design example is Nature’s design in which different artifacts are grown in the entire system as a single entity In contrast, engineers fabricate various parts and assemble them together At present, we do not have bio-logical manufacturing processes but we have plenty of opportunities for innovation by learning and imitating the no-assembly designs of the natural
compliant Nature tries to make the design compliant, whereas engineers traditionally make the structure and mechanism stiff Ananthasuresh and
the conventional steel stapler with no-assembly design Compliant mecha-nisms are single-piece, flexible structures that deliver the desired motion by undergoing elastic deformation as opposed to rigid body motion
5.2 Design Problems
The defect or quality problem in the product is caused by three things: bad design, bad material, and wrong manufacturing process For example, if the product is correctly designed, and if the manufacturing method is not cor-rectly designed, then the product will be defective Similarly, an incorcor-rectly
Trang 2a tool that guides the designer in coming up with better design choices and then provides the optimum design It is a tool for concept generation, concept approval, and concept improvement It integrates processing knowledge into the design of a part to obtain maximum benefits and capabilities of the manufacturing method To come up with the best design, the manufacturing engineer should have a good knowledge of the benefits and limitations of various composite manufacturing techniques The team members should also
be familiar with tools such as design for manufacturing (DFM), design for assembly (DFA), etc for developing high-quality design As compared to metals, composite materials offer the highest potential of utilizing DFM and part integration, and therefore can significantly reduce the cost of production Engineers utilizing isotropic materials such as aluminum and steel tradi-tionally fabricate parts by first selecting raw materials from a design hand-book based on performance requirements Once the raw material is selected, the manufacturing process to fabricate the part is identified This philosophy
is not viable in the field of composite materials With engineered composite materials, the material selection, design, and manufacturing processes all merge into a continuum philosophy embodying both design and manufac-ture in an integrated fashion For example, a rod produced by filament winding, pultrusion, RTM, or braiding would impart distinct stiffness, damping, and mass characteristics due to different fiber and resin distribu-tions and fiber volume fracdistribu-tions Composites manufacturing processes create distinct microstructural properties in the product
The best design example is Nature’s design in which different artifacts are grown in the entire system as a single entity In contrast, engineers fabricate various parts and assemble them together At present, we do not have bio-logical manufacturing processes but we have plenty of opportunities for innovation by learning and imitating the no-assembly designs of the natural
compliant Nature tries to make the design compliant, whereas engineers traditionally make the structure and mechanism stiff Ananthasuresh and
the conventional steel stapler with no-assembly design Compliant mecha-nisms are single-piece, flexible structures that deliver the desired motion by undergoing elastic deformation as opposed to rigid body motion
5.2 Design Problems
The defect or quality problem in the product is caused by three things: bad design, bad material, and wrong manufacturing process For example, if the product is correctly designed, and if the manufacturing method is not cor-rectly designed, then the product will be defective Similarly, an incorcor-rectly
Trang 3Manufacturing Techniques
6.1 Introduction
Every material possesses unique physical, mechanical, and processing char-acteristics and therefore a suitable manufacturing technique must be utilized
to transform the material to the final shape One transforming method may
be best suited for one material and may not be an effective choice for another material For example, wood is very easy to machine and therefore machin-ing is quite heavily utilized for transformmachin-ing a wooden block to its final shape Ceramic parts are difficult to machine and therefore are usually made from powder using hot press techniques In metals, machining of the blank
or sheet to the desired shape using a lathe or CNC machine is very common
In metals, standard sizes of blanks, rods, and sheets are machined and then welded or fastened to obtain the final part In composites, machining of standard-sized sheets or blanks is not common and is avoided because it cuts the fibers and creates discontinuity in the fibers Exposed and discon-tinuous fibers decrease the performance of the composites Moreover, the ease of composites processing facilitates obtaining near-net-shape parts Composites do not have high pressure and temperature requirements for part processing as compared to the processing of metal parts using extrusion, roll forming, or casting Because of this, composite parts are easily trans-formed to near-net-shape parts using simple and low-cost tooling In certain applications such as making boat hulls, composite parts are made at room temperature with little pressure This lower-energy requirement in the pro-cessing of composites as compared to metals offers various new opportuni-ties for transforming the raw material to near-net-shape parts
There are two major benefits in producing near-net- or net-shape parts First, it minimizes the machining requirement and thus the cost of machin-ing Second, it minimizes the scrap and thus provides material savings There are cases when machining of the composites is required to make holes or to create special features The machining of composites requires a different approach than machining of metals; this is discussed in Chapter 10