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Advanced Manufacturing Technology

Module 5.1

Concurrent Engineering and Rapid Prototyping

© Dr. R.Siriram 10 January 2006, adapted from McCord, K,R; Eppindeger, S,D, August 1993

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Views of the Enterprise Model• The enterprise model consists of several interrelated view models.

• Each view describes a specific aspect of the enterprise and has its own modeling method.

• Some of these views include:

• Process view: Takes a major role in defining, establishing, analyzing, and extracting the business process of a company. It fulfills the requirements of transforming the business process, manufacturing process and product-development process into a process view model.

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Views of the Enterprise Model• Typical modeling tools for process view include WFMC (Workflow management coalition),

• Function view: The function view is used to describe the functions and their relationships in a firm.

• These functions fulfill the objectives of the company, such as sales, order planning, product design, part manufacturing, and human resource management.

• Typical modeling tools for the function view include IDEF (0)

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• Information View: The information view organizes the information necessary to support the enterprise function and process using an information model.

• Organization View: Is used to define and represent the organization model of the firm. The model includes the organization tree, team, faculty, role and authority. In an organization view, the relationships between different organization entities are defined.

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• Resource View: Is similar to the organization view. It describes resources used by the processes to fulfill the firm’s business functions.

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Rapid Prototyping• Rapid Prototyping (RP) can be defined as a group of techniques used to fabricate a scale model of a part or assembly using 3-dimensional computer aided design (CAD) data.

• Rapid Prototyping has also been referred to as solid free-form manufacturing, automated manufacturing, and layered manufacturing.

• RP has obvious use a tool for visualization.

• In addition, RP models can be used for testing, such as where shape is put into a wind tunnel.

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Rapid Prototyping• RP models can be used to create male models for tooling, such as silicone rubber models and investment casts.

• In some cases can be the final part, but typically the RP material is not strong or accurate enough.

• When RP material is suitable, highly convoluted shapes (including parts within parts) can be produced because of the nature of RP)

• There is a multitude of experimental RP methodologies either in development by small groups or individuals.

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Why Rapid Prototyping?• The reasons for Rapid Prototyping are:

• To increase effective communication.

• To decrease development time.

• To decrease costly mistakes.

• To minimize sustaining engineering changes.

• To extend product lifetime by adding necessary changes and eliminating features early in the design.

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Why Rapid Prototyping?• The trends in manufacturing industries continue to emphasize the following:

• Increasing number of variants or products.

• Increasing product complexity.

• Decreasing product lifetime before obsolescence.

• Decreasing delivery time.

• Rapid prototyping improves product development by enabling better communication in a concurrent engineering environment.

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Methodology for Rapid Prototyping?• The basic methodology for all concurrent rapid prototyping techniques can be summarized as follows:

• A CAD model is constructed, then converted to STL format. The resolution set to minimize stair stepping.

• The RP machine processes the .STL file by creating sliced layers of the part.

• The first layer of the physical model is created. The model then lowers the thickness of the next layer, and the process is repeated until completion

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Methodology for Rapid Prototyping?• of the model.

• The model and any supports are removed. The surface of the model is finished and cleaned.

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Rapid Prototyping• RP techniques that are commercially available, include Stereolithography (SLA), Selective Sintering, Solid Ground Curing (SGC), and Ink Jet Printing Techniques.

Highlights of Stereolithography • The first RP technique and is still most widely used.

• Inexpensive compared to other techniques.

• Uses light-sensitive liquid polymer.

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• Requires post-curing since laser is not of high enough power to complete.

• Long-term curing can lead to warping.

• Parts are quite brittle and have a tacky surface.

• No milling step so accuracy in Z can suffer.

• Support structures are typically required.

• Process is simple: There are no milling or masking steps required.

• Uncured material can be toxic. Ventilation is a must

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Stereolithography

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Stereolithography Process

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Stereolithography Process-supports for weak parts

• During fabrication, if extremities of the part become too weak, it may be necessary to use supports to prop up the model

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Highlights of Selective Laser Sintering• Patented in 1989.

• Considerably stronger than SLA; sometimes structurally functional parts possible.

• Laser beam selectively fuses powder materials: nylon, elastomer and..S

• Advantage over SLA: Variety of materials and ability to approximate co engineering plastic materials.

• No milling step so accuracy in Z can differ.

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Highlights of Selective Laser Sintering• Process is simple: There are no milling or masking steps required.

• Living hinges are possible with thermoplastic-like materials.

• Powdery, porous surface unless sealant is used. Sealant also strengthens.

• Uncured material is easily removed after a build by brushing or blowing.

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SLA vs SLS• Material properties: The SLA process is limited to photo resins which are typically brittle. The SLS process can utilize polymer powder when sintered, approximate thermoplastics quite well.

• Surface finish: The surface of an SLS part is powdery, like the base material particles are fused together without complete melting. SLA is a better process where fine, accurate surface is required. However, a varnish-like coating can be applied to SLS parts to strengthen them.

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SLA vs SLS• Dimensional accuracy: SLA is more accurate immediately after completion of the model.

• Support structures: SLA parts typically need support structures during the process. SLS parts, because of the supporting powder, sometimes do not need any supports but this depends upon part configuration.

• Machining properties: In general, SLA materials are brittle and difficult to machine whereas SLS thermoplastic-like materials are easily machined.

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SLA vs SLS• Size: SLS and SLA parts can be made from the same size, but if sectioning of a part is required, SLS parts are easier to bond.

• Investment Casting: The investment casting industry has been conservative moving to RP male models, so SLS made from traditional waxes are preferred.