Digital Modeling and Rapid Prototyping

Digital ModelingandRapid PrototypingPROJECT SUBMITTED BY:MURTAZA LOKHANDWALAMUSTAFA PARDAWALADigital modelingDigital modeling is a process that joins design with the construction/production through use of 3D modeling software and additive and subtractive manufacturing processes.These tools allow designers to produce digitally materiality, which is something greater than of an image on a screen, and actually tests the accuracy of the software and computer lines.Architects can propose complex surfaces, where the properties of material should put the design

Machines for digital modeling:1. COMPUTER NUMERICAL CONTROL (CNC)

2. LASER CUTTER

3. 3-D PRINTERS

MACHINES for fabricationsCNC router: CNC stands for computer numerical control. Through a computer controller , g-codes are read which represent specific CNC functions in alphabetical format. The g-codes drive a machine tool, a powered mechanical device used to fabricate componentsCNC machines are specifically successful in milling materials such as plywood, foam boards, and steels at a fast speed.

CNCLASER CUTTERUsed to cut materials such as chip board, matte board, felt, wood, and acrylic up to 3/8" (1cm) thickness.

The laser cutter is often bundled with a driver software which interprets vector drawings produced by any number of CAD software platforms.

It is able to modulate the speed of the laser head, as well as the intensity and resolution of the laser beam.

Objects cut out of materials can be used in the fabrication of physical models.

3D PRINTERS Use a variety of methods and technology to assemble physical versions of digital objects. A thin layer of an object is constructed at a time and then building another layer of the same object immediately on top of the prior one. Uses a 3-axis robotic system that extrudes material, one thin layer at a time and progressively builds up a shape. . Examples of machines are: Dimension 768 and the Ultimaker.

Rapid Prototyping (RP) A family of fabrication processes developed to make engineering prototypes in minimum lead time based on a CAD model of the item Traditional method is machiningCan require significant lead-times several weeks, depending on part complexity and difficulty in ordering materials RP allows a part to be made in hours or days, given that a computer model of the part has been generated on a CAD system7RAPID PROTOTYPINGTechnology which considerably speeds the iterative product development processIt is a group of techniques used to quickly fabricate a scale model of a physical part or assembly using a 3D computer aided design(CAD).

Fig: a) Examples of parts made by rapid prototyping b) Stereolithography model of cellular phoneWhy is Rapid Prototyping Important?Product designers want to have a physical model of a new part or product design rather than just a computer model or line drawing Creating a prototype is an integral step in designA virtual prototype (a CAD model of the part) may not be sufficient for the designer to visualize the part adequately Using RP to make the prototype, the designer can see and feel the art and assess its merits and shortcomings.9More About Rapid PrototypingAlternative names for RP:Layer manufacturing Direct CAD manufacturing Solid freeform fabricationRapid prototyping and manufacturing (RPM) RP technologies are being used increasingly to make production parts and production tooling, not just prototypes10CLASSIFICATION OF RAPID PROTOTYPINGRapid prototyping is classified to 3-major groups:

Subtractive ( Removal of material )

Additive ( Adding of material )

Virtual ( Advanced computer base visualization)Subtractive ProcessSubtractive process use computer based Prototype technology to speed the process

Essential Technologies for subtractive prototyping :

Computer based drafting packages ( 3-D representation of parts)

Interpretation software (Translation of cad file to manufacturing software)

Manufacturing Software (Planning Machining operations)

Computer-Numerical Control MachinerySUBTRACTIVE PROTOTYPING

ADDITIVE PROTOTYPING Additive prototyping refers to a class of manufacturing processes, in which a part is built by adding layers of material upon one another. Theydo not require custom tooling or planned tool movements. The part is constructed directly from a digital 3-D model created through Computer Aided Design (CAD) software. Advantages: speed, part complexity, material types, low-volume production.

Virtual prototypingVirtual prototyping is the modeling and simulation of all aspects of a prototype, i.e. mechanical design, kinematics, dynamics, and controls accompanied by a realistic visualization.

Realizing the best design in the shortest lead-time of complex products/processes

Allows the exotic, unconventional designs be prototyped, rapidly and cost-effectively CLASSIFICATION OF RP TECHNOLOGIES LIQUID BASED

SOLID BASED

POWDER BASED

1. Liquid-Based Rapid Prototyping SystemsStarting material is a liquid About a dozen RP technologies are in this categoryIncludes the following processes: StereolithographySolid ground curingDroplet deposition manufacturing17A. Stereolithiography

Here a photosensitive liquid resin which forms a solid polymer when exposed to ultraviolet light is used.the reaction only takes place near the surface and voxels of solid polymeric resin are formed.machine consists of a build platform (substrate), which is mounted in a vat of resin and a UV laser.Here the first layer is scanned, the platform is then lowered and held at that position for the proper settlement of the liquid polymer.After this a new layer is scanned and the process is continued.B. Solid Ground Curing (SGC)Like stereolithography, SGC works by curing a photosensitive polymer layer by layer to create a solid model based on CAD geometric data Instead of using a scanning laser beam to cure a given layer, the entire layer is exposed to a UV source through a mask above the liquid polymer Hardening takes 2 to 3 s for each layer19Figure 34.4 SGC steps for each layer: (1) mask preparation, (2) applying liquid photopolymer layer,(3) mask positioning and exposure of layer, (4) uncured polymer removed from surface, (5) wax filling, (6) milling for flatness and thickness.

Solid Ground Curing20C. Droplet Deposition Manufacturing (DDM)Starting material is melted and small droplets are shot by a nozzle onto previously formed layer

Droplets cold weld to surface to form a new layer

Deposition for each layer controlled by a moving x-y nozzle whose path is based on a cross section of a CAD geometric model that is sliced into layers

Work materials include wax and thermoplastics

212. Solid-Based Rapid Prototyping SystemsStarting material is a solidSolid-based RP systems include the following processes: Laminated object manufacturing Fused deposition modeling22Laminated Object ManufacturingConsists of layers which are adhesively bonded to one another

Uses layer of paper or plastic sheets with heat activated glue on one side of the product parts

Excess material to be removed manually

Simplified by preparing the laser to burn perforations in cross-sectional pattern

LOM uses sheets as thin as 0.05mm

Compressed paper has appearance and strength of soft wood , and often mistaken for elaborate wood carvings

Fused Deposition Modeling

Fused Deposition Modeling (FDM) is process in which a movable nozzle deposits threads of molten polymeric material.

The build material is heatedslightly above its melting temperature so that it solidifies within a very short time and after extrusion it welds to the previous layer.

Fig : (a)Fused-deposition-modeling process. (b)The FDM 5000, a fused-decomposition-modeling-machine. Recent FDM systemsinclude two nozzles, one for part material and other for support material.

Support material is relatively of poor quality and can be broken easily once the complete part is deposited and removed.ApplicationsDesigners are able to confirm their design by building a real physical model in minimum time using RP.Existence of part allows certain engineering analysis and planning activities to be accomplished that would be more difficult without the physical entity.Also applicable in various industries such as aerospace, automotive, biomedical, electronics etc.

25AdvantagesCAD data files can be manufactured in hours.

Tool for visualization and concept verification.

Prototype used in subsequent manufacturing operations to obtain final part

Tooling for manufacturing operations can be produced

Decreasing delivery time.

To increase effective communication.Problems with Rapid PrototypingMaterial issuesHigh prices of the equipmentsForming accuracy and quality issuesThe problem of softwareA single featureDuring part deposition generally two types of errors are observed:Curing errors: are due to over or under curing with respect to the curing line.Control errors: due to variation layer thickness and scan position.

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