Micro and nano grinding
Post on 12-Apr-2017
Micro and Nano Grinding
Micro and Nano Grinding7ME6.1A (Part III)
Er. Mohit OstwalAssistant ProfessorDepartment of Mechanical EngineeringJodhpur Institute of Engineering and Technology-Coed
Conventional GrindingHorizontal Wheel surface grinding
Vertical spindle surface grinding
Conventional GrindingCreep feed grinding
Outside Diameter cylindrical grinding
Conventional GrindingInternal grinding with chucking machine
workpiece is supported by a blade instead of by centers or chucks. Two wheels are used. The larger one is used to grind the surface of the workpiece and the smaller wheel is used to regulate the axial movement of the workpiece.
Conventional GrindingJig Grinding
Double disk Grinding
Conventional GrindingThread Grinding
Micro Grinding and Ultra Precision ProcessIn order to achieve fully ductile mode grinding, material removal must take place at the nanoscale. The nanogrinding process is a process that relies on using a nickel coated ceramic material with microscale diamond particles bonded to it that are cubo-octahedral in shape to machine nanoscale features in a variety of workpiece materials. The diamonds are bonded to the piezoelectric material by gaseous deposition, laser cladding or directly bonding a porous tool to the material via an adhesive paste. The process is executed by applying a known sinusoidal frequency to the piezoelectric crystal in order to achieve a desired oscillatory displacement.Rapid vibration of the crystal will allow material removal rates to be increased, thus making it a nanomanufacturing process. The nanogrinding process is accompanied by wear of the diamond grains, and the rate of this wear plays an important role in determining the efficiency of the nanogrinding process and the quality of the nanomachined surface. Wear mechanisms in nanogrinding processes appear to be similar to that of single-point cutting tools, the only difference being the size of swarf particles generated.
Ultraprecision GrindingUsing this machine coupled with ductile mode theory, mirror finishes can be achieved on the workpiece without the intervention of polishing.Dimensional accuracy in the range of a few micrometersSurface form accuracy in the range of lOO nm or better.Surface texture in the range of 5nm, or better.Speed range of 10,000 -70,000 rpm.Grinding wheels from 3 mm - 15 mm in diameter. Sometimes 30 mm(small aspheric components, particularly lenses and lens molds).
Ultraprecision GrindingThe machine is capable of generating arbitrary confocal shapes on materials ranging from optical glass and infrared materials to non-ferrous metals, crystals, polymers, and ceramics.The machine temperature is maintained stable to less than 0.5 C. Grinding is done in a flood-cooled environment.Machine has two vertical spindles with hydrostatic bearing of high precision and rigidity.It can machine at extremely fine depth of cut (0.1 |Lim) and capable of producing at submicron flatness and nanometer surface Micro grinding roughness (5 nm Rmax) on optical glass (NbF), Mn-Zn ferrite and electronic materials using diamond abrasive grinding wheels.
Piezoelectric Nano grinding Process
Piezoelectric Nano grinding ProcessPiezoelectricEffect is the ability of certain materials to generate an electric charge in response to applied mechanical stress.The process relies on applying an electric current to the diamond coated piezoelectric material that causes material to strain.When the diamond coated piezoelectric material is placed in closed proximity to substrate, the diamond removes extremely small fragments of substrate, when the electric current is applied to the material.The magnitude of the applied current controls the material removal rate.Used to process the biomedical materials especially in the production of nanoscale ducts and channels in micro and nanofluidic devices.Asubstrateis a solid substance or medium to which another substance is applied and to which that second substance adheres.
Nanogrinding apparatusHolding a polished specimen between the jaws of a vise so that a piezoelectric crystal oscillator traverses back-and-forth across the specimen, thus machining the specimen by creating a cut depth between the diamonds adhered on the piezoelectric crystal and the workpiece material.The work pieces are mounted in a vise that was attached to a x-y-z linear slide in order to achieve accurate positioning of the workpiece.The piezoelectric crystal was mounted on a steel framework that was orthogonal to the workpiece. The whole unit was located within a tetrahedral space frame to dampen excess vibrations.
Nanogrinding ToolsPorous nanogrinding tools are composed of abrasive particles (sub micron) embedded in vitrified bond.
Vitrified bonds are composed of glasses that are formed when clays, ground glass frits, mineral fluxes (feldspars & chemical fluxes such as forax) melt when grinding wheel is fixed at temperature in range 1000C to 1200 C.
NANOGRINDINGSOME TERMS RELATED TO NANOGRINDINGFrits- Pre-grounded glass with a predetermined oxide content.
Flux- Low MP silicious clay that reduces surface tension at bond bridge abrasive grain interface.
Pre-fitted bond- Bond that contains no clay minerals.
Clays are used to provide to provide vitrified grinding wheels with green strength during heat treatment process.
Bonding Layer is approx. a few micrometer in thickness and is caused by use of high clay content bonding system.
Preparation of Nanogrinding WheelsRaw materials use are:1. Hymen Prima Ball Clay2. Standard poreclain clay3. Potash Feldspar4. Synthetic QuartzFollowing Analysis are performed:Chemical AnalysisRational Analysis- Mineralogical composition of raw materials.Fusible Bonding system Ball Clay (66 wt%) and Feldspar (34 wt%)In general Ball clay (12.77 wt%) and Feldspar (4.93 wt%) quartz.Raw materials are mixed in mortar, pressed in a mold and fired at various temperatures. Heating rate of 2.9 C/min. (950 to 1050 C).Cooled down at a rate of 1.8 C/min. To avoid thermal fracture.