Group 4 11/16/05The Process of grindingWork piecesNaturally Occurring AbrasivesGrinding WheelsSlide 6Common Grinding WheelsSuperabrasive wheelsTypes of BondsSlide 10Grinding FormulaChip FormationConsiderations while grindingWheel wearGrinding RatioShaping grinding wheelsGrindingHow Grinding Is UsedTypes of grinding MachinesSlide 20Slide 21Slide 22Slide 23Slide 24Slide 25Slide 26Process of Chem. MillingElectrochemical Machining (ECM)Slide 29Parts From Electrochemical MillSlide 31Design Considerations for ECMElectrochemical Grinding (ECG)Slide 34Slide 35Electrical discharge machiningSlide 37Slide 38Slide 39Slide 40Laser-Beam MachiningDesign consideration with LBMSlide 43Electron-Beam MachiningSlide 45Slide 46Water Jet MachiningSlide 48Slide 49Slide 50Slide 51Slide 52Abrasive water jet machiningReferencesGroup 411/16/05David ReisJeremy HuckinsAlberto BarrazaNick MelladyThe Process of grindingGrinding – a chip removal process that uses an individual abrasive grain as the cutting tool.Work piecesCylindrical, conical, fillets, helical, concave, slotting, internal grindingNaturally Occurring AbrasivesEmery, corundum, quartz, garnet, diamondGrinding WheelsStructure, wear, and fracture patternsGrinding Wheels•The surface of grinding wheels are made up of these grains.•Grains have random irregular shapes that are located at the edge of the grinding wheels.Common Grinding WheelsColored surfaces indicate grinding facesSuperabrasive wheelsColored surfaces indicate grinding facesTypes of BondsVitrified (ceramic bond) – most common type of bond. Resistant to water, oil, and acids. Sometimes made with steel backing plates to improve physical strength.Resinold (thermosetting resins) – Also known as organic wheels. Resistant to extremely high temperaturesReinforced Wheels – Made with layers of fiberglass. If it did break it would not disintegrate, it would just crack.Types of BondsThermoplastic – sol-gel abrasives bonded with thermo plasticsRubber – the most flexible bond. Metal – lowest cost. Used mainly in small quantity productionGrinding FormulaL = (Dd)Undeformed length = (Diameter)(depth)Chip Formation•When a chip forms ridges are formed where the chip left the material. This is known as plowing.Considerations while grindingTemperatureIf it gets too high it can:Affect surface properties, including metallurgical changeCause residual stress on the work pieceCause distortions in the work piece, therefore accuracy goes downWheel wearOnce a wheel starts wearing it becomes less accurateGrain wear – grains become flat and dullBond fracture – the bond breaks and the grains come off the wheelGrinding RatioG = Volume of material removedThese vary widely, ranging from 2 to 200+Using grinding fluids can increase the life of a grinding wheel 10 fold.Volume of wheel wearShaping grinding wheels•The edges of grinding wheels are shaped with diamond dressing tools controlled by computers.•Shaping the wheel sharpens it and restores its accuracy.GrindingAlmost any material can be ground - aluminum, steel, ceramics, even diamond or glass.Grinding is used whenever something needs to be smoothed or shaped.Grinding is used to form countless types of products such as automobile engines, sharp edges on knives, ball bearings and drills. The smooth, accurate surface of the Hubble Telescope lens was formed by a process of grinding and polishing. How Grinding Is UsedTypes of grinding MachinesSurface grinderCylindrical grinderUniversal Tool and Cutter Grinder Lapping and Polishing•Cylindrical grinding center cylindrical grinding centerless.The bench grinderChemical Milling @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@• chemical milling/blanking is a chemical process that dissolves material from unmasked (unprotected) areas of metallic parts immersed in a tank of heated and agitated chemical reagents. The term "blanking" denotes small, thin workpieces, and "milling" indicates relatively large workpieces. (a) Schematic illustration of the chemical machining process. Note that no forces or machine tools are involved in this process.(b) Stages in producing a profiled cavity by chemical machining; note the undercut.•considerable advantages compared to punching, laser-cutting and wire-erosion(left) Missile skin-panel section contoured by chemical milling to improve the stiffness to-weight ratio of the part.(top) Weight reduction of space launch vehicles by chemical millingaluminum-alloy plates. These panels are chemically milled after the plates have first been formedinto shape by processes such as roll forming or stretch forming.Chemical milling is used to reduce the overall weight and other non desirable factors of a workpieceProcess of Chem. Milling1. Artwork and Negative PreparationAn image is printed by a program with a laser plotter directly to the film at any size needed2. Photoresist Application / Exposure / DevelopApply Photoresist coating to make the metal sensitive to light.Expose coated metal to UV light source which applies the image from the art work to the metal part.Treat exposed metal part with a developing solution which removes the soft portion of the Photoresist.3. Etching / Resist RemovalProcess the metal through chemical etcher which dissolves all metal not protected by the hardened photoresist coating.Electrochemical Machining (ECM)uses an electrolyte at a high rate from the tool piece to wash away the metal ions from the workpiecethe tool is usually solid or tubular formMaterial removal rate is 1.5 – 4mm³ECM was developed in 1929Not as widely used as other processesGenerally used to make complex cavities and shapes Finishes parts burr-free and bright surfacesNever has any thermal damage to part or wear on the toolsParts From Electrochemical MillReplacement KneesDesign Considerations for ECMECM is not suitable for producing sharp edges or flat sufacesFlow of electrolyte can become difficultDesigns should make provision for a small taper for holes to be machinedElectrochemical Grinding (ECG)•Process that combines electrochemical machining with conventional grinding•Grinder wheel is embeded with abrasive particles of dimond or aluminum oxideAbrassives on the spindle have two functionsTo act as insulators between the wheel and workpieceTo remove electrolytic products