RAPID PROTOTYPING

RAPID PROTOTYPINGINTRODUCTION OF RAPID PROTOTYPINGIs a revolutionary and powerful technology with wide range of application.The process of prototyping involve quick building up of a prototype or working model for the purpose of testing the various design features, ideas,concepts,funtionality,output and performance.HISTORY OF RAPID PROTOTYPINGIn 60s ,the first rapid prototyping technique became accessible in the later eighties and used for production of prototype and model parts.In 70s ,Herbert Voelcker, engineering professor developed the basic tools of mathematics that clearly describe the three dimensional aspects and resulted in the earliest theories of algorithmic and mathematical theories for solid modeling.In 80s, Carl Deckard ,researcher from the University of Texas. He pioneered the layer based manufacturing , he thought of building up the model layer by layer. He printed 3D models by utilizing laser light for fusing metal powder in solid prototypes,single layer at a time. Technique called Selective Laser Sintering.Nowadays , the computer engineer has to simply sketch the ideas on the computer screen with the help of a design program that is computer aided. Computer aided designing allows to make modification as required and can create a physical prototype that is a precise and proper 3D object.THE ADVANTAGE OF RAPID PROTOTYPINGCAD data files can be manufactured in hours.Tool for visualization and concept verification.Prototype used in subsequent manufacturing operation to obtain final part.Tooling for manufacturing operation can be produce.SUBTRACTIVE PROCESSIs the prevent process in the history of model making. Model makers once utilized materials like clay and wood or other hard material, to whittle, carve, or sculpt a model component. The excess material was basically chiseled, cut, and sanded to expose the design within the carving medium. This process was understandably time intensive and resulted in a finished product that was a one of a kind and could not be easily replicated without remaking the part from scratch.ADDITIVE PROCESSIs built by adding layers of material upon one another.This process are inhenrently different from subtractive processes or consolidation processes. Example such as milling ,turning or drilling, use carefully planned tool movement to cut away material from a workpiece to form the desired part.The part is constructed directly from a digital 3D model created through Computer Aided Design (CAD) software.VIRTUAL PROCESSTo create each virtual cross section in then takes physical form layer after until an identical prototype model is created.THE FUSED DEPOSITION MODELLING (FDM)Process constructs three-dimensional objects directly from 3D CAD data. A temperature controlled head extrudes thermoplastic material layer by layer.This model is oriented and mathematically sliced into horizontal layers varying from +/- 0.127 0.254mm thickness.The system operates in X, Y and Z axes, drawing the model one layer at a time.

STEREOLITHOGRAPHYis an additive manufacturing process using a vat of liquid UV curable photopolymer resin and UV laser to build parts a layer at a time.The laser beam traces a part cross section pattern on the surface of the liquid resin.After a pattern has been traced, the SLAs elevator platform descends by a single layer thickness, typically 0.05mm to 0.15mm. Then, a resin filled blade sweeps across the part cross section,recoating it with fresh material.

SELECTIVE LASER SINTERING (SLS)Is a layer additive production process that creates three dimensional object using CO2 laser to melt, or sinter and fuse selective powder molecules based on information supplied by a computer aided design (CAD) file.Commonly called thermoplastic material or in some cases, thermoplastic binders for use in metals. Allows for these materials to be fused together in tiny layers ranging between .003 and .006.Parts and or assemblies that move and work that have a good surface finish and feature detail.SLS gives the capability of flexible snaps and living hingers as well as high stress and heat tolerance. BALLISTICThe BPM personal modeler came with all hardware and software enclosed in one compact unit.The BPM utilized ink jet or droplet based manufacturing techniques, it builds the models by firing micro droplets of molten wax material from a moving nozzle or jet onto a stationary platform, the platform then lowers and the process is repeated for each layer of the model.The parts can be scaled, rotated or translated to a desired orientation. This is performed on a 5 axis workstation.LAMINATEDThat uses a carbon dioxide laser to create successive cross section of a three dimentional object from layers of paper with a polythylene coating on the backside. The first step is to creates a base om which the paper can attach itself.

HIGHLIGHTS OF LAMINATED OBJECT MANUFACTURINGLayers of glue-backed paper form the model.Low cost:Raw material is readily availabel.Large parts: Because there is no chemical reaction involved,parts can be made quite large.Accuracy in z is less than that for sterrolithography and selective laser sintering . No milling stepOutside of model,cross hatching removes materialModel should be sealedin order to prohibit moisture.Before sealing ,models have a wood-like texture.Not as prevalent as stereolithograhy and selective laser siterning.METHODOLOGY FOR RP PROCESS The basic methodology for all current rapid prototyping techniques can be summarized as follows:

A CAD model is constructed, then converted STL format . The resolution can be set to minimize stair stepping.The RP machine processes the STL file by creating sliced layers of the model.The fisrt layer of the physical model is created .The model is then lowered by the thickness of the next layer, and the process is repeated until completion of the modelThe model and any supports are removed. The surface of the model is then finished and cleaned. RAPID TOOLINGA process that is the result of combining Rapid Prototyping techniques with conventional tooling practices to produce a mold quickly or part of a functional model from CAD data in less time and at lower cost relative to traditional machining method .Rapid Tooling can act as brige to production injection molded parts.The main advantage are tooling time is much shorter than for a conventional tool. Time to first articles can be less than one fifth that of conventional tooling; tooling cost is much less than for a conventional tool. Cost can be below five percent of conventional tooling cost.The main challrnges are tool life is less than for conventional tools and tolerances are wider than for conventional tools.

TYPES OF RAPID TOOLING PROCESS-Low Volume (from tens to hundreds)- Soft tooling-Reaction injection molding-Bridge Tooling Direct Access Injection Molding Intermediate (from hundreds to thousands)- Metal filled epoxy tooling- Powdered metal tooling - space puzzle molding