Prototype
Design Analysis Process
Rapid Prototyping What is rapid prototyping? A process that generates physical objects directly from geometric data without traditional tools
Rapid Prototyping What is Rapid Prototyping? a CAD technique to allow Automatic creation of a physical model or prototype from a virtual 3-D model. Create a 3-D Photocopy of a part. Computer -> Real life
Rapid Prototyping Why use Rapid Prototyping Decreases lead time Facilitates concurrent engineering Allows visualization of more ideas
Applications of Rapid Prototyping Prototype for design evaluation Prototype for function verification Rapid tooling processes
Rapid Prototyping OR OR OR
RP eliminates the following problems compared to other manufacturing processes: Feature based design Defining of blank geometry Defining different steps or complex sequences Considering clamping, jigs or fixtures Designing and manufacturing of molds and dies
Main stages in Rapid Prototyping 1- Creating cross sections of part 2- Deposition of sections of layers 3- Formation and combining layers
Layer Formation Methods Solid Liquid Powder Bulk Liquid Polymerization 1 Component Selective Laser Sintering Component & Binder 3D Printing & Gluing Gluing Sheets Laminated Object Manufacturing Polymerization Foil Polymerization Light Heat Thermal Polymerization Melting & Solidification Shape Melting Fused Deposition Modeling Ballistic Particle Manufacturing Lamps Lasers Solid Base Curing Photosolid. Layer at a Time Stereolithography
Stereo Lithography Stereo Lithography (SLA) was the first commercially available Solid Freeform Manufacturing system (1986). It is still the industry leader, setting many industry trends. 1) Laser traces current cross section onto surface of photo curable liquid resin 2) Polymer solidifies when is hited by the laser s intense UV light 3) Elevator lowers hardened cross section below liquid surface 4) Laser prints the next cross section directly on top of previous 5) After entire 3-d part is formed it is post-cured (UV light)
Mirror Stereolithograpy Overview Optics Laser Elevator Laser is focused/shaped through optics. A computer controlled mirror directs laser to appropriate spot on photopolymer surface. Polymer solidifies wherever laser hits it. When cross section is complete, elevator indexes to prepare for next layer.
SLA Interface 3-D Systems had to develop an interface between CAD systems and their machine STL files (*.stl) were developed by 3-D systems to allow CAD systems to interface with their machine Many CAD programs now can export the *.stl file for easy conversion from CAD to part
STL Files (*.stl) A boundary representation style was used, with all surfaces being approximated by polygons or groups of polygons *.stl files use triangles or groups of triangles to approximate all surfaces Obviously, one can never exactly form curved or rounded surfaces with triangles-- the accuracy of the model depends on the size of the triangles Triangles are all assigned a normal vector, which represents the outward surface normal Parts are defined by representing all their bounding surfaces as faceted surfaces, using the triangular patches
Processing of *.stl Files After the CAD system has generated *.stl file, it can be passed to the SLA machine Machine then processes the *.stl file, slicing it into many thin layers stacked on one another. The resulting files are called slice files. The shapes in each of the slices are the cross sections that the modeler will make In SLA (and in many SFM processes) thick solid sections of material are often removed and replaced with cross hatching Thus SLA parts are usually hollow, with cross hatching on the inside to add strength/stability
Stereo Lithography Apparatus
Manifold produced by SLA
Parts produced by SLA
Medical application
12/18/2014 Support Structure
(Photo solidification Layer at a Time) 1) Cross section shape is printed onto a glass mask 2) Glass mask is positioned above photopolymer tank 3) Another rigid glass plate constrains liquid photopolymer from above 4) UV lamp shines through mask onto photopolymer- light only can pass through clear part, polymer solidifies there, polymer in masked areas remains liquid 5) New coat of photopolymer is applied 6) New mask is generated and positioned, and process repeats 7) 12-15 minute post cure is required
Layer at a Time Solidification Mask is then placed under an ultraviolet lamp UV Lamp Clear Plate Glass Mask Photopolymer A glass mask is generated (using an electro-statically charged toner) Laser then shines through mask, solidifying the entire layer in one shot. Result is much more rapid layer formation, and more thorough solidification. (Light strikes every where.)
Solid Ground Curing (SGC) 1) Cross section shape is printed onto a glass mask 2) Glass mask is positioned above photopolymer tank 3) UV lamp shines through mask onto photopolymer- light only can pass through clear part, polymer solidifies there, polymer in masked areas remains liquid 4) All excess polymer is removed- part is again hit with UV light 5) Melted wax is spread over workpiece, filling all spaces 6) Workpiece is precisely milled flat 7) Glass is erased and re-masked, workpiece is placed slightly below surface in photopolymer, process repeats 8) After fabricating part, wax is melted and removed. Accurate, no support or post cure needed, but expensive & toxic
Solid Ground Curing Cycle Photopolymer UV Lamp Glass Mask Generate glass mask Shine UV Lamp through mask to solidify photopolymer Wax Remove excess polymer, and fill gaps with liquid wax. Chill to solidify wax. Chiller Liquid Wax Solid Wax Workpiece Wax Mill wax & workpiece Coat with photopolymer Milling Cutter
Fused Deposition Modeling (FDM) 1) A spool of thin plastic filament feeds material to FDM head 2) Inside FDM, filament is melted by a resistance heater 3) The semiliquid thermoplastic is extruded through FDM head 4) Material is deposited in a thin layer on formation 5) Material solidifies, forming a laminate 6) Next layer is formed on previous- lamina fuse together
FDM Layer Formation Filament Heated FDM Head Molten Filament FDM generated cross section Supply Notice that the FDM filament cannot cross itself, as this would cause a high spot in the given layer
Produced by FDM
3-D Printing Direct Shell Production Casting (DSPC) First creates a disposable mold which is used to cast actual part 1) Thin distribution of powder is spread over powder bed 2) Inkjet print heads deposit small droplets of binder 3) Upon contact, binder droplets join powder to form solid 4) Piston supporting powder bed lowers so that the next layer can be spread and joined 5) Process repeats until completion 6) The shell that has been created is fired 7) Shell is filled with molten metal 8) Metal solidifies & shell is broken away from part Process allows use of metal for parts. Uses alumina powder & silica binder for shell. 3-D printing can have other uses.
3-D Printing Process Powder Bed Binder Print- head Printhead Powder Bed "Fast" Axis Piston "Slow" Axis
3-D Printing Part
Selective Laser Sintering (SLS) 1) A cartridge feeding system deposits a thin layer of heat fusible powder into a workspace container 2) The layer of powder is heated to just below its melting point 3) Laser traces the cross section. Particles hit by laser are heated to sintering point and bond into a solid mass. 4) A new layer of material is deposited on top of previous layer 5) Process repeats SLS modelers use nylon/polycarbonate powders, which are health hazards (dangerous to breathe). SLS does not require external support of overhangs, as loose powder provides support for new layers. Improvements in SLS technology have expanded allowed materials to ABS, PVC, and metals encapsulated in plastic. Some powdered metals have been directly sintered.
SLS Process Powder Bed Mirror Optics Laser Powder Bed Leveling Roller Piston Powder Feeding System
SLS Process
Laminated Object Manufacturing (LOM) 1) Sheet of material is laminated onto existing stack-up 2) Laser perforates the outline of cross section into top sheet (cross section is NOT completely cut out- full sheet remains) and outer sheets are cut by laser hatching 3) Edges of top sheet are trimmed to match rest of stack-up 4) Next layer is bonded and process repeats 5) When finished- have solid block with perforations separating the actual workpiece from extra material. Extra material must be removed & part is sanded. LOM modelers use paper w/ polyester adhesive. They pose no health hazards and can be set up in offices. Further they are comparatively inexpensive, and require no supports for any overhangs. Unfortunately, LOM modelers also require more post-processing work (removing part from block).
LOM Process Mirror Laser Cut "edge" of layer Heated Roller Optics Lamination Material Perforate Workpiece Boundary Take-up Reel Platform Supply Reel Cross Hatch "Excess Material"
Produced by LOM Process
Ballistic Particle Manufacturing (BPM) Employs a technology called Digital Microsynthesis 1) Molten plastic is fed to a piezoelectric jetting mechanism, similar to those on inkjet printers. 2) A multi-axis controlled NC system shoots tiny droplets of material onto the target, using the jetting mechanism. 3) Small droplets freeze upon contact with the surface, forming the surface particle by particle. Process allows use of virtually any thermoplastic (no health hazard) & offers the possibility of using material other than plastic.
BPM Process Ejector Head Has multi-axis control to "aim" droplet stream Droplets of Molten Material Build Platform
Laser Engineered Net Shaping