2. Introduction
• Chemical machining
• Electro chemical machining
• Electrical discharge machining
• Wire EDM
• Laser beam machining
• Electron-beam machining and plasma-arc
cutting
• Water-jet machining
• Abrasive-jet machining
• Nanofabrication
• Micro machining
• Economics of advanced machining process
3. Situations where processes are not
satisfactory, economical or even possible
• High hardness and the strength of the material
• Work-piece too flexible
• Complex shape
• Surface finish and dimensional tolerances
• Undesirable Temperature rise and dimensional
tolerances
4. Examples of parts made by advanced Machining
Processes
Fig : Examples of parts made by advanced machining processes. These parts are made by advanced machining
processes and would be difficult or uneconomical to manufacture by conventional processes. (a) Cutting
sheet metal with a laser beam.(b) Microscopic gear with a diameter on the order of 100µm, made by a special
etching process.
5. Chemical machining
Chemical attacks metals and etch them by removing small
amounts of material from the surface using reagents or etchants
Fig : (a) Missile skin-panel section contoured by chemical milling to improve the stiffness-to weight
ratio of the part. (b) Weight 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. The design of the chemically machined rib
patterns can be modified readily at minimal cost.
6. Chemical milling:
milling
• Shallow cavities produced on plates, sheets, forgings, and
extrusions
Procedure for chemical milling Steps :
1 – Residual stresses should relieved in order to prevent warping
2 – Surfaces to be thoroughly degreased and cleaned
3 - Masking material(tapes,paints,elastomers & plastics ) is applied
4 – masking is peeled off by scribe and peel technique
5 – The exposed surfaces are etched with etchants
6 – After machining the parts to be thoroughly washed to prevent further
reactions with residue etchant
7 – rest of the masking material is removed and the part is cleaned and
inspected
8 – additional finishing operations are performed on chemically milled
parts
9 – this sequence is repeated to produce stepped cavities and various
contours
7. Process capabilities:
• Chemical milling used in the aerospace industry
• Tank capacities for reagents are as large as 3.7m
x15m
• Process also used for micro electronic devices
• Surface damage may result due to preferential etching
and intergranular attack
Chemical blanking:
• Chemical blanking is similar to chemical milling
• Material is removed by chemical dissolution rather
than by shearing
• Burr free etching of printed-circuit boards, decorative
panels, thin sheet metal stampings as well as
production of small and complex shapes
8. Chemical Machining
Fig : (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 machining; not the
undercut.
9. Photochemical blanking :
• Modification of chemical milling
• Material removed from flat thin sheet by photographic
techniques
10. Steps for photochemical blanking
• Design is prepared at a magnification of 100x
• Photographic negative is reduced to the size of finished
part
• Sheet blank is coated with photosensitive material
(Emulsion)
• Negative placed over coated blank and exposed to ultra
violet light which hardens the exposed area
• Blank is developed which dissolves the exposed areas
• Blank is then immersed into a bath of reagent or sprayed
with the reagent which etches away the exposed areas
• The masking material is removed and the part is washed
thoroughly to remove all chemical residues
11. Design considerations
• Designs involving sharp corners,deep & narrow cavities,
severe tapers or porous work piece should be avoided
• Undercuts may be developed because etchant attacks
both in horizontal and vertical direction
• To improve production rate the bulk of the work piece
should be shaped by other machining process priorly
• Dimensional variations can occur ,this can be minimized
by proper selection of artwork media by controlling the
environment
• Many product designs are now made with computer
aided design
12. Electro Chemical Machining
Fig : Schematic illustration of the electrochemical-machining
process. This process is the reverse of electroplating.
13. Electrochemical machining
• This process is reversal of the electro plating
• Electrolyte acts as current carrier
• High rate of electrolyte movement in tool work piece gap washes
metal ions away from the work piece ( ANODE)
• This is washed just before they have a chance to plate on the tool
( cathode)
• Shaped tool made of brass , copper , bronze , or stainless steel
• Electrolyte is pumped at a high rate through the passages in the
tool
• Machines having current capacities as high as 40,000 A and as
low as 5A are available
14. Parts made by Electrochemical Machining
Fig : Typical parts made by electrochemical machining. (a) Turbine blade made of a nickel alloy, 360
HB; note the shape of the electrode on the right. (b) Thin slots on a 4340-steel roller-bearing cage.
(c) Integral airfoils on a compressor disk.
15. Process capabilities
• Used to machine complex cavities in high strength
material
• Applications in aerospace industry,jet engines parts
and nozzles
• ECM process gives a burr free surface
• No thermal damage
• Lack of tool forces prevents distortion of the part
• No tool wear
• Capable of producing complex shapes and hard
materials
16. Biomedical Implant
Fig : (a) Two total knee replacement systems showing metal implants (top pieces) with an ultrahigh
molecular weight polyethylene insert (bottom pieces) (b) Cross-section of the ECM process as
applied to the metal implant.
17. Design considerations for Electrochemical
Machining
• Electrolyte erodes sharp surfaces and profiles so not
suited for sharp edges
• Irregular cavities may not be produced to the desired
shape with acceptable dimensional accuracy
• Designs should make provisions for small taper for
holes and cavities to be machined
Pulsed electro chemical machining(PECM)
• Refinement of ECM
• Uses pulsed rather than direct
• Improves fatigue life, eliminates recast layer left on die
and mold surfaces by electrical discharge machining
• Very high current densities, but the current is
18. Electrochemical Grinding
Combines electrochemical machining with conventional grinding
Fig : Schematic illustration of the electrochemical – grinding process. (b) Thin slot
produced on a round nickel – alloy tube by this process.
19. Electrical-Discharge Machining
(a) (b) (c)
Fig : (a) Schematic illustration of the electrical-discharge machining process. This is one of the most widely used
machining processes, particularly for die-sinking operations. (b) Examples of cavities produced by the
electrical-discharge machining process, using shaped electrodes. Two round parts (rear) are the set of dies for
extruding the aluminum the aluminum piece shown in front. (c) A spiral cavity produced by ECM using a
slowly rotating electrode, similar to a screw thread.
20. Examples of EDM
Fig : Stepped cavities produced with a square
electrode by the EDM process. The workpiece
moves in the two principal horizontal
directions (x-y), and its motion is
synchronized with the downward movement
of the electrode to produce these cavities.
Also shown is a round electrode capable of
producing round or elliptical cavities.
Fig : Schematic illustration of producing an inner cavity by EDM, using a specially designed
electrode with a hinged tip, which is slowly opened and rotated to produce the large cavity.
21. WIRE EDM
Fig : (a) Schematic
illustration of the wire
EDM process. As
much as 50 hours of
machining can be
performed with one
reel of wire, which is
then discarded. (b)
Cutting a thick plate
with wire EDM. (c) A
computer-controlled
wire EDM machine.
22. Laser Beam Machining
Fig : (a) Schematic illustration of the laser-beam machining process. (b) and (c) Examples
of holes produced in nonmetallic parts by LBM.
23. Laser-Beam Machining
Fig : Schematic illustration of the electron-beam machining process. Unlike LBM, this process requires a
vacuum, so workpiece size is limited to the size is limited to the size of the vacuum chamber.
24. Water Jet Machining
Fig : (a) Schematic illustration of water-jet
machining. (b) A computer-controlled, water-
jet cutting machine cutting a granite plate. (c)
Example of various nonmetallic parts produced
by the water-jet cutting process.
26. Nanofabrication
Fig : (a) A scanning electron microscope view of a diamond-tipped (triangular piece at the
right) cantilever used with the atomic force microscope. The diamond tip is attached to
the end of the cantilever with an adhesive. (b) Scratches produced on a surface by the
diamond tip under different forces. Note the extremely small size of the scratches.
