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Rapid Prototyping_April18_2022.ppt

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Rapid Prototyping_April18_2022.ppt

  1. 1. RAPID PROTOTYPING(RP) 1. Fundamentals of Rapid Prototyping 2. Rapid Prototyping Technologies 3. Applications and Benefits of Rapid Prototyping
  2. 2. Introduction Rapid Prototyping (RP) techniques are methods that allow designers to produce physical prototypes quickly. It consists of various manufacturing processes by which a solid physical model of part is made directly from 3D CAD model data without any special tooling. The first commercial rapid prototyping process was brought on the market in 1987. Nowadays, more than 30 different processes (not all commercialized) with high accuracy and a large choice of materials exist. These processes are classified in different ways: by materials used, by energy used, by lighting of photopolymers, or by typical application range.
  3. 3. Rapid Prototyping Technique In the Rapid Prototyping process the 3D CAD data is sliced into thin cross sectional planes by a computer. The cross sections are sent from the computer to the rapid prototyping machine which build the part layer by layer. The first layer geometry is defined by the shape of the first cross sectional plane generated by the computer. It is bonded to a starting base and additional layers are bonded on the top of the first shaped according to their respective cross sectional planes. This process is repeated until the prototype is complete.
  4. 4. Rapid Prototyping Rapid Prototyping: Traditional manufacturing: additive material subtractive material
  5. 5. Rapid prototyping A technology that produces models and prototype parts from 3D CAD model data, computed tomography(CT) and Magnetic Resonance Imaging(MRI) scan data, and model data created from 3D object digitizing systems with minimum lead time. RP systems join together liquid, powder and sheet materials to form parts Layer by layer, RP machines fabricate plastic, wood, ceramic and metal objects RP also known as Solid Freeform Fabrication (SFF) or Layer Manufacturing (LM)
  6. 6. Basic process of Rapid Prototyping Three stages: pre-processing, building, and post processing Build Prototype RP Process Post Process Pre Process Generate .STL file Build Supports if needed Slicing Remove Supports Clean Surface Post Cure if needed Part Completed CAD Model Surface/Solid Model in RP systems in CAD
  7. 7. Why 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 design • A 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 part and assess its merits and shortcomings ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e
  8. 8. RP – Two Basic Categories: 1. Material removal RP - machining, using a dedicated CNC machine that is available to the design department on short notice • Starting material is often wax • Easy to machine • Can be melted and resolidified • The CNC machines are often small - called desktop machining 2. Material addition RP - adds layers of material one at a time to build the solid part from bottom to top ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e
  9. 9. Starting Materials in Material Addition RP 1. Liquid monomers that are cured layer by layer into solid polymers 2. Powders that are aggregated and bonded layer by layer 3. Solid sheets that are laminated to create the solid part Additional Methods • In addition to starting material, the various material addition RP technologies use different methods of building and adding layers to create the solid part • There is a correlation between starting material and part building techniques ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e
  10. 10. Steps to Prepare Control Instructions 1. Geometric modeling - model the component on a CAD system to define its enclosed volume 2. Tessellation of the geometric model - the CAD model is converted into a computerized format that approximates its surfaces by facets (triangles or polygons) 3. Slicing of the model into layers - computerized model is sliced into closely-spaced parallel horizontal layers ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e
  11. 11. Figure 34.1 Conversion of a solid model of an object into layers (only one layer is shown). ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e Solid Model to Layers
  12. 12. More About Rapid Prototyping • Alternative names for RP: • Layer manufacturing • Direct CAD manufacturing • Solid freeform fabrication • Rapid prototyping and manufacturing (RPM) • RP technologies are being used increasingly to make production parts and production tooling, not just prototypes ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e
  13. 13. Classification of RP Technologies • There are various ways to classify the RP techniques that have currently been developed • The RP classification used here is based on the form of the starting material: 1. Liquid-based 2. Solid-based 3. Powder-based ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e
  14. 14. 1. Liquid-Based Rapid Prototyping Systems • Starting material is a liquid • About a dozen RP technologies are in this category • Includes the following processes: I. Stereolithography II. Solid ground curing III. Droplet deposition manufacturing ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e
  15. 15. Stereolithography (STL) RP process for fabricating a solid plastic part out of a photosensitive liquid polymer using a directed laser beam to solidify the polymer • Part fabrication is accomplished as a series of layers - each layer is added onto the previous layer to gradually build the 3-D geometry • The first addition RP technology - introduced 1988 by 3D Systems Inc. based on the work of Charles Hull • More installations than any other RP method ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e
  16. 16. Stereolithography: (1) at the start of the process, in which the initial layer is added to the platform; and (2) after several layers have been added so that the part geometry gradually takes form. Stereolithography
  17. 17. Figure 34.3 A part produced by stereolithography (photo courtesy of 3D Systems, Inc.). ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e
  18. 18. Facts about STL • Each layer is 0.076 mm to 0.50 mm (0.003 in to 0.020 in.) thick • Thinner layers provide better resolution and more intricate shapes; but processing time is longer • Starting materials are liquid monomers • Polymerization occurs on exposure to UV light produced by laser scanning beam • Scanning speeds ~ 500 to 2500 mm/s ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e
  19. 19. Part Build Time in STL Time to complete a single layer : ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e where Ti = time to complete layer i; Ai = area of layer i; v = average scanning speed of the laser beam at the surface; D = diameter of the “spot size,” assumed circular; and Td = delay time between layers to reposition the worktable d i i T vD A T  
  20. 20. Part Build Time in STL - continued Once the Ti values have been determined for all layers, then the build cycle time is: ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e where Tc = STL build cycle time; and ni = number of layers used to approximate the part  Time to build a part ranges from one hour for small parts of simple geometry up to several dozen hours for complex parts    i n i i c T T 1
  21. 21. 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 layer ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e
  22. 22. Figure 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. ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e Solid Ground Curing
  23. 23. Facts about SGC • Sequence for each layer takes about 90 seconds • Time to produce a part by SGC is claimed to be about eight times faster than other RP systems • The solid cubic form created in SGC consists of solid polymer and wax • The wax provides support for fragile and overhanging features of the part during fabrication, but can be melted away later to leave the free-standing part ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e
  24. 24. 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 ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e
  25. 25. Solid-Based Rapid Prototyping Systems • Starting material is a solid • Solid-based RP systems include the following processes: • Laminated object manufacturing • Fused deposition modeling ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e
  26. 26. Laminated Object Manufacturing (LOM) Solid physical model made by stacking layers of sheet stock, each an outline of the cross- sectional shape of a CAD model that is sliced into layers •Starting sheet stock includes paper, plastic, cellulose, metals, or fiber-reinforced materials •The sheet is usually supplied with adhesive backing as rolls that are spooled between two reels •After cutting, excess material in the layer remains in place to support the part during building ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e
  27. 27. Figure 34.5 Laminated object manufacturing. ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e Laminated Object Manufacturing
  28. 28. Fused Deposition Modeling (FDM) RP process in which a long filament of wax or polymer is extruded onto existing part surface from a workhead to complete each new layer •Workhead is controlled in the x-y plane during each layer and then moves up by a distance equal to one layer in the z-direction •Extrudate is solidified and cold welded to the cooler part surface in about 0.1 s •Part is fabricated from the base up, using a layer-by-layer procedure ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e
  29. 29. Fused Deposition Modeling (FDM Part constructed by deposition of melted plastic 1. A 0.05” wire of plastic pulled from a spool into head 2. Plastic is melted 3. Molten plastic extruded through the pen nozzle to build layer Z-motion Melting head with XY-motion Build material wire spools: (a) Part (b) Support Extrusion nozzles Part Support Foam base Materials: ABS, Polycarbonate (PC), Polyphenylsulfonen (PPSF)
  30. 30. FDM™ is a patented technology of Stratasys™ Inc Monkey Cinquefoil Designed by Prof Carlo Sequin, UC Berkeley 5 monkey-saddles closed into a single edged toroidal ring Gear assembly Toy design using FDM models of different colors
  31. 31. 3.Powder-Based RP Systems • Starting material is a powder • Powder-based RP systems include the following: • Selective laser sintering • Three dimensional printing ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e
  32. 32. Selective Laser Sintering (SLS) Moving laser beam sinters heat-fusible powders in areas corresponding to the CAD geometry model one layer at a time to build the solid part •After each layer is completed, a new layer of loose powders is spread across the surface •Layer by layer, the powders are gradually bonded by the laser beam into a solid mass that forms the 3-D part geometry •In areas not sintered, the powders are loose and can be poured out of completed part ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e
  33. 33. Selective Laser Sintering (SLS) Technology invented at Sandia Labs, USA, Part constructed with metal powder 1.High power laser melts site of deposition 2. Powder deposited by nozzle into hot- spot 3.Laser builds cross-section in raster-scan fashion 4.Table lowered by layer thickness 5.New layer constructed on top of previous layer 6.Repeat process till build is complete
  34. 34. Selective Laser Sintering (SLS) Machine
  35. 35. Example of Selective Laser Sintering (SLS) [source: www.optomec.com]
  36. 36. Application Range • Visual Representation models • Functional and tough prototypes • cast metal parts Advantages • Flexibility of materials used • PVC, Nylon, Sand for building sand casting cores, metal and investment casting wax. • No need to create a structure to support the part • Parts do not require any post curing except when ceramic is used. Disadvantages • During solidification, additional powder may be hardened at the border line. • The roughness is most visible when parts contain sloping (stepped) surfaces.
  37. 37. Three Dimensional Printing (3DP) Part is built layer-by-layer using an ink-jet printer to eject adhesive bonding material onto successive layers of powders •Binder is deposited in areas corresponding to the cross sections of part, as determined by slicing the CAD geometric model into layers •The binder holds the powders together to form the solid part, while the unbonded powders remain loose to be removed later •To further strengthen the part, a sintering step can be applied to bond the individual powders ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e
  38. 38. Figure: Three dimensional printing: (1) powder layer is deposited, (2) ink-jet printing of areas that will become the part, and (3) piston is lowered for next layer (key: v = motion). ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e Three Dimensional Printing
  39. 39. Three Dimensional Printing
  40. 40. RP Applications • Applications of rapid prototyping can be classified into three categories: 1. Design 2. Engineering analysis and planning 3. Tooling and manufacturing ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e
  41. 41. Design Applications • Designers are able to confirm their design by building a real physical model in minimum time using RP • Design benefits of RP: • Reduced lead times to produce prototypes • Improved ability to visualize part geometry • Early detection of design errors • Increased capability to compute mass properties ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e
  42. 42. Engineering Analysis and Planning • Existence of part allows certain engineering analysis and planning activities to be accomplished that would be more difficult without the physical entity • Comparison of different shapes and styles to determine aesthetic appeal • Wind tunnel testing of streamline shapes • Stress analysis of physical model • Fabrication of pre-production parts for process planning and tool design ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e
  43. 43. Tooling Applications • Called rapid tool making (RTM) when RP is used to fabricate production tooling • Two approaches for tool-making: 1. Indirect RTM method 2. Direct RTM method ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e
  44. 44. Indirect RTM Method Pattern is created by RP and the pattern is used to fabricate the tool • Examples: • Patterns for sand casting and investment casting • Electrodes for EDM ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e
  45. 45. Direct RTM Method RP is used to make the tool itself • Example: • 3DP to create a die of metal powders followed by sintering and infiltration to complete the die ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e
  46. 46. Manufacturing Applications • Small batches of plastic parts that could not be economically molded by injection molding because of the high mold cost • Parts with intricate internal geometries that could not be made using conventional technologies without assembly • One-of-a-kind parts such as bone replacements that must be made to correct size for each user ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e
  47. 47. Problems with Rapid Prototyping • Part accuracy: • Staircase appearance for a sloping part surface due to layering • Shrinkage and distortion of RP parts • Limited variety of materials in RP • Mechanical performance of the fabricated parts is limited by the materials that must be used in the RP process ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e

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