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Advanced Manufacturing Processes

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Title: Advanced Manufacturing Processes


1
Chapter 1. Machining
2
M.Tech 1st year
  • MI 572 Advanced Manufacturing
    Processes
  • LTP 3 1 2/2
  • Weight-age Mid term 20
  • End term 40
  • Practical class work 2020
  • Credit 04

3
DIAMOND TURNING

4
INTRODUCTION
  • Diamond turning is a process of mechanical
    machining of precision elements using lathes or
    derivative machine tools (e.g., turn-mills,
    rotary transfers) equipped with natural or
    synthetic diamond-tipped tool bits.
  • The process of diamond turning is widely used to
    manufacture high-quality aspheric optical
    elements from crystals, metals, acrylic, and
    other materials.

5
PROCESS
  • Diamond turning is a multi-stage process.
  • Initial stages of machining are carried out using
    a series of CNC lathes of increasing accuracy.
  • A diamond-tipped lathe tool is used in the final
    stages of the manufacturing process to achieve
    sub-nanometre level surface finishes and
    sub-micrometre form accuracies.

6
  • Quality of surface finish and form accuracy is
    monitored throughout the manufacturing process
    using such equipment as contact and laser
    profilometers, laser interferometers, optical and
    electron microscopes.
  • Temperature control is crucial, because the
    surface must be accurate on distance scales
    shorter than the wavelength of light. Temperature
    changes of a few degrees during machining can
    alter the form of the surface enough to have an
    effect.

7
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8
TYPES OF TURNING
  • TRADITIONAL TURNING is a turbocharged version of
    classic lathe work. The part is chucked on a
    lathe having an incredibly accurate spindle and
    slides. An ultra sharp diamond of extremely
    accurate nose radius is used to turn and face the
    part. The CNC interpolation of the X and Z axis
    of the machine can produce arbitrary rotationally
    symmetric parts. In principle it is just as easy
    to produce the parabola of a reflecting telescope
    as it is to produce a basic cylindrical shape.

9
  • OFF-AXIS TURNING is an approach where a workpiece
    is mounted to the spindle in an asymmetric
    fashion. This allows cutting of multiple parts
    simultaneously or producing contours whose
    rotational center is not coincident with the
    center of the part. Certain optical
    configurations take advantage of this approach.

10
  • FLY-CUTTING AND MILLING reverses the position of
    work and tool. The tool is mounted to the
    spindle and the work is mounted to the slide.
    This allows the generation of flat or elliptical
    surfaces.

11
MATERIAL THAT CAN BE MACHINED USING SPDT
  • Plastics
  • Acetal
  • Acrylic
  • Nylon
  • Polycarbonate
  • Polypropylene
  • Polystyrene
  • Zeonex

12
  • Metals
  • Aluminum and aluminium alloys
  • Brass
  • Copper
  • Gold
  • Electroless nickel plating on other materials
  • Silver
  • Tin
  • Zinc

13
  • Infrared crystals
  • Cadmium sulfide
  • Cadmium telluride
  • Calcium fluoride
  • Cesium iodide
  • Gallium arsenide
  • Germanium
  • Lithium niobate
  • Potassium bromide
  • Potassium dihydrogen phosphate (KDP)

14
APPLICATIONS
  • The process of diamond turning is widely used to
    manufacture high-quality aspheric optical
    elements from crystals, metals, acrylic, and
    other materials like-
  • assemblies in telescopes
  • video projectors
  • missile guidance systems
  • Lasers
  • scientific research instruments
  • numerous other systems

15
DRAWBACK
  • Ferrous materials are not readily machinable
    because the carbon in the diamond tool chemically
    reacts with the substrate, leading to tool damage
    and dulling after short cut lengths.
  • Several techniques have been investigated to
    prevent this reaction, but few have been
    successful for long diamond machining processes
    at mass production scales.

16
HYBRID MACHINING

17
INTRODUCTION
  • Technological improvement of machining processes
    can be achieved by combining different machining
    actions or phases to be used on the material
    being removed for eg-
  • A mechanical conventional single cutting or MA
    action process can be combined with the
    respective machining phases of electrodischarge
    (ED) in electrodischarge machining (EDM)

18
NEED OF HYBRID MACHINE
  • To make use of the combined advantages and to
    avoid or reduce some adverse effects the
    constituent processes produce when they are
    individually applied.
  • The performance characteristics of a hybrid
    process are considerably different from those of
    the single-phase processes in terms of-
  • Productivity
  • Accuracy
  • Surface quality

19
DIFFERENT PROCESS COMBINATION AND APPLICATION
20
HYBRID CHEMICAL AND ELECTROCHEMICAL PROCESSES.

21
  • In this family of hybrid machining processes, the
    major material removal phase is either CD or ECD.
  • machining action can be combined with the thermal
    assistance by local heating in case of
    laser-assisted electrochemical machining (ECML).

22
HYBRID THERMAL MACHINING PROCESS

23
  • the main material removal mechanism is a thermal
    one.
  • The combination of this phase with the ECD phase,
    MA action, and ultrasonic (US) vibration
    generates a family of double action processes.
  • The triplex hybrid machining is also achievable
    by combining the electrodischarge erosion (EDE)
    phase, the ECD action, and the main grinding (G)
    as shown in above fig 1.9.

24

25
MICRO MACHINING

26
INTRODUCTION
  • Refers to techniques for fabrication of 3D
    structures on the micrometer scale
  • Applications include MEMS devices e.g. airbag
    sensor, medical devices, micro-dies and molds,
    etc.
  • Most methods use silicon as substrate material

27
BASICS OF MICROMACHINING
  • Two Different Approaches of Micromachining
  • Bulk or Surface
  • Fundamental Four Techniques of Micromachining
  • Thin Film Deposition
  • Photolithography
  • Etching
  • Sacrificial Release

28
PHOTOLITHOGRAPHY

29
  • The wafers are chemically cleaned to remove
    particulate matter, organic, ionic, and metallic
    impurities
  • High-speed centrifugal whirling of silicon wafers
    known as "Spin Coating" produces a thin uniform
    layer of photoresist (a light sensitive polymer)
    on the wafers
  • Photoresist is exposed to a set of lights through
    a mask often made of quartz
  • Wavelength of light ranges from 300-500 nm (UV)
    and X-rays (wavelengths 4-50 Angstroms)

30
ETCHING
  • Process Variations
  • Wet etching
  • Dry etching

31
WET ETCHING
  • The key ingredients are
  • Oxidizer (e.g. H2O2, HNO3)
  • Acid or base to dissolve the oxidized surface
    (e.g. H2SO4, NH4OH)
  • Dilutent media to transport the products through
    (e.g. H2O)

32
DRY ETCHING

THE ABOVE FIG SHOWS PLASMA BASED ETCHING PROCESS
PRODUCTS MANUFACTURED BY ETCHING
33
THIN FILM DEPOSITION
  • Chemical Vapor Deposition

34
  • sputtering

35
  • evaporation

36
BULK OR SURFACE
  • Process for producing 3D MEMS structures older
    process
  • Uses anisotropic etching of single crystal
    silicon

37
SURFACE
  • Newer process for producing MEMS structures
  • Uses etching techniques to pattern microscale
    structures from polycrystalline (poly)silicon, or
    metal alloys

38
APPLICATIONS
  • MEMS
  • medical device
  • Fabrication etc.

39
Thank You
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