ME260 Mechanical Engineering Design IIForming and Shaping Processes/EquipmentForming and Shaping Plastics and Composite MaterialsSlide 4Slide 5Slide 6Slide 7Rapid Prototyping OperationsSlide 9Slide 10Machining FundamentalsSlide 12Cutting-Tool MaterialsMachining Round ObjectsSlide 15Slide 16Different Machining Operations: MillingSlide 18Different Machining Operations: SawingSlide 20Grinding WheelCylindrical Grinding OperationsThread GrindingAdvanced Machining Processes: Chemical MillingAdvanced Machining Processes: Chemical MachiningAdvanced Machining Processes: Laser-Beam Machining (LBM)Advanced Machining Processes: Electron-Beam MachiningAdvanced Machining Processes: Water-Jet MachiningSmall-scale Machining: Clean RoomsSmall-scale Machining: Microelectronic DevicesSmall-scale Machining: Film DepositionSmall-scale Machining: LithographySmall-scale Machining: Isotropic and Anisotropic EtchingSmall-scale Machining: MEMSSmall-scale Machining: Bulk MicromachiningSmall-scale Machining: Surface MicromachiningSmall-scale Machining: MEMS ExampleME260 Mechanical Engineering Design IIInstructor notesForming and Shaping Processes/EquipmentCastingRolling (metals)Forging (metals)Extrusion and Drawing (metals)Sheet-metal FormingMetal-Powder ProcessingGlass and Ceramic ProcessingForming and Shaping Plastics/CompositesRapid PrototypingMachining OperationsForming and Shaping Plastics and Composite MaterialsMany ways that we’ve learned before apply to forming and shaping plasticsExamples are: casting, extrusion, different molding operations (i.e. the plastic fills a mold)Forming and Shaping Plastics and Composite MaterialsExample 1: Casting (applies to both thermoplastics and thermosets)A typical application is covering an electric coil. Here, the plastic serves as a dielectric or an insulatorForming and Shaping Plastics and Composite MaterialsExample 2: ThermoformingHeat is used to mold a plastic sheet, assisted by vacuum or air pressureUsed for thermoplasticsSome applications: packaging trays for cookies and candy, and advertising signsForming and Shaping Plastics and Composite MaterialsExample 2: Molding of Reinforced PlasticsResin and reinforcement (e.g. carbon and boron fibers) are mixed at the time of moldingCan be applied in layers using (a) hand lay-up or (b) Spray lay-upSome applications: Boat hulls, swimming poolsForming and Shaping Plastics and Composite MaterialsExample 2: Metal Matrix Composites (MMCs)Typically a relatively soft matrix (e.g. aluminum) and hard reinforcement particles (e.g. SiC)Can be done by casting the molten metal with the high melting-point reinforcementSome applications: Brake rotorsSiCAluminumRapid Prototyping OperationsDefinition: Relatively fast production of a single example (or prototype) of a designed product or system before actual large-scale productionNeed: for design evaluation and troubleshooting especially of complex parts/systems(a)(a)Rapid Prototyping OperationsPrototype is typically built layer by layer to replicate a 3-D CAD drawingOne method is using FDM (Fused-Deposition-Modeling) --- each layer is composed of multiple deposited lines of plastic that fuse togetherCommercial machines start at about $25kRapid Prototyping OperationsAnother method is StereolithographyMethod based on the principle of curing (hardening) a liquid photopolymer into a specific shapeMachining FundamentalsClassic machining of materials is based on the concept that a harder/stronger material with a sharp edge is able to cut through another softer/weaker materialThis is typically done by chipping away, i.e. cutting, a layer at a timeMachining FundamentalsCutting produces “chips”Chips typically represent scrap (i.e. wasted material), need to be cleaned up, and can be hazardousChip hazards: small high-temperature and high-velocity flying objects (discontinuous chips), as well as long continuous chips that can serve as distraction for the operatorSafety: personal safety equipment (e.g. special eye protection goggles, work clothes), protective shields or enclosures, chip breakers, lubrication fluids to reduce temperature, among othersRubbing (friction) causes heat generationCutting-Tool MaterialsPosses the following characteristics- Hot hardness (maintains hardness at hot temperatures)- Toughness and impact strength (mechanical shock)- Thermal shock resistance- Wear resistance- Chemically inert or stable (not flammable or does not interact with the cut material)Examples:- High-speed steel (HSS), which are highly alloyed steels- Carbides (tungsten or titanium carbides in a cobalt or nickel-molybdenum matrix, respectively)- Cobalt alloys- Diamond or Cubic Boron NitrideMachining Round ObjectsMachining Round ObjectsDrilling and Reaming (for cylindrical holes)(a)(a)Machining Round ObjectsTapping (making threads in cylinders or cylindrical holes)Different Machining Operations: MillingMilling cutters and operationsDifferent Machining Operations: MillingMilling cutters and operationsDifferent Machining Operations: SawingVarious sawing operationsDifferent Machining Operations: SawingSaw tooth typesCut width (at least, why?)Grinding WheelThe structure, wear and fracture patterns in a grinding wheelSimilar to the concept of sawing and filing (e.g. using sand paper). The idea is to use small hard particles or grains to chip away at the surface of the machined part.The pores allow for cooling and space for chipsThe breakage of bonds and grains allows for re-sharpening of the cutting surfaceCylindrical Grinding OperationsVarious cylindrical grinding operationsThread GrindingThread grinding by (a) traverse, and (b) plunge grinding.Advanced Machining Processes: Chemical MillingWeight reduction of space launch vehicles by chemical milling aluminum-alloy plates. These panels are chemically milled after the plates have first been formed into shape by processes such as roll forming or stretch forming.Advanced Machining Processes: Chemical MachiningSchematic illustration of the chemical machining process. Note that no forces or machine tools are involved in this process. Note also that the mask does not react with the reagent Reagent=etchant (typically an acid)Advanced Machining Processes: Laser-Beam Machining (LBM)Schematic illustration of the laser-beam machining process.Concept: use laser power to cut through material by melting or evaporating it awayCan cut metals, plastics or ceramicsAdvanced Machining Processes: Electron-Beam MachiningSchematic illustration of the electron-beam